Time Of Primary Immunization Research Articles

α-Galatosylceramide and retinoic acid regulate splenic follicular B cell differentiation and antibody production in a CD1d-dependent manner

Abstract α-Galactosylceramide (αGalCer) and all-trans-retinoic acid (RA) are each potent immune regulators able to increase immune responses in various conditions. αGalCer is particularly known for its direct activation of invariant NKT cells and B cells. In the present study, we used wildtype (WT) and CD1d knockout (KO) mice to characterize the specificity of αGalCer and its interaction with RA on B cell activation. WT and CD1dKO spleen cells were cultured ± αGalCer (100 ng/ml), or LPS (100 ng/ml) as a direct B-cell stimulus, and RA (20 nM), and B cell proliferation and differentiation were determined by flow cytometry. αGalCer and LPS both markedly increased the CD19+ B cell division. Whereas αGalCer mainly enriched spleen follicular CD23+ B cells, LPS increased the marginal zone CD21+ B cell population. The effects of αGalCer were completely absent in CD1dKO mice. However, although spleen B cells of CD1dKO mice failed to respond to αGalCer, these cells had a higher rate of proliferation compared to cells of WT mice, suggesting that CD1d molecules may have immune tonic effects in addition to reacting to αGalCer. Moreover, RA worked together with αGalCer to increase the proportions of IgG+ and CD138+ cells among CD23+ B cells, suggesting enhanced B-cell differentiation in splenic follicles. An in vivo immunization study using Keyhole limpet hemocyanin (KLH, 50 μg, ip) further confirmed that administration of RA (37 μg, po) and αGalCer (2 μg, sc), given at the time of primary immunization, increased antibody production in both the primary and secondary responses, which was not observed in CD1dKO mice. Thus, immune enhancement by αGalCer requires CD1d, and, when combined with RA promotes follicular B cell differentiation and increased antibody production.

α-Galactosylceramide stimulates splenic lymphocyte proliferation in vitro and increases antibody production in vivo in late neonatal-age mice.

The neonatal stage is characterized by weak responses to various infections and vaccines, thus the development of efficient formulas to improve vaccine effectiveness is of high priority. The glycolipid alpha galactosylceramide (αGalCer) is known as a potent immune modulator due mainly to natural killer (NK) T cell activation. Using a mouse tetanus toxoid (TT) immunization model, we observed that neonatal mice given αGalCer at the time of primary immunization on postnatal day (pnd) 17 had a significantly higher TT-specific immunoglobulin (Ig)M response as well as a memory IgG response, while αGalCer given on pnd 7 resulted in only marginal boosting. Consistently, immunostaining of the spleen sections from αGalCer-treated pnd 17 immunized neonates showed a higher number of Ki67(+) cells in the splenic germinal centre area, suggesting a stronger response after immunization. In-vitro kinetic studies revealed that spleen cells from newborn to pnd 7 neonates did not respond to αGalCer stimulation, whereas cell proliferation was increased markedly by αGalCer after pnd 7, and became dramatic around neonatal pnd 17-18, which was accompanied by increased B, T and NK T cell populations in the spleen. In addition, in pnd 17 spleen cells, αGalCer significantly stimulated the production of NK T cytokines, interleukin (IL)-4 and interferon (IFN)-γ, and promoted the proliferation of CD23(+) B cells, a subset of B cells enriched in germinal centres. These data suggest that αGalCer is an effective immune stimulus in the late neonatal stage, and thus may be useful in translational studies to test as a potential adjuvant to achieve a more efficient response to immunization.

α-galactosylceramide may lead to an enhanced affinity immune response (IRC3P.459)

Abstract α-galactosylceramide (αGalCer) has been shown to stimulate B cell proliferation in mice, leading to enhanced antibody titers. We sought to discover whether, in addition to antibody titer, we could develop a higher affinity immune response in mice administered αGalCer in the context of our standard, adjuvant based immunization methodologies. Mice were immunized three times, every 4-6 weeks, with various antigens emulsified in Freund’s adjuvant. Test animals were administered αGalCer at the time of primary immunization, in addition to the antigen. Relative affinity was determined by testing serum antibody for reactivity to limiting concentrations of solution phase antigen. Results show that, for some antigen systems, administration of αGalCer does result in a trend toward a higher relative affinity vs. control animals. Pooled data from 3 antigen systems shows an average relative affinity of 2.105 nM for αGalCer mice vs. 3.134 nM for control mice. It was also observed, for one antigen system, that only those animals administered αGalCer developed a significant immune response. Our results indicate that administration of αGalCer at the time of primary immunization may lead to a slightly higher average affinity response in mice and can also be the difference between the development of a significant immune response vs. a very weak response.

α-Galactosylceramide stimulates splenic lymphocyte proliferation in vitro and increases antibody production in vivo in the late neonatal-age mouse. (VAC12P.1028)

Abstract The neonatal stage is characterized by weak responses to various infections and vaccines; thus the development of efficient formulas to improve vaccine effectiveness is of high priority. The glycolipid alpha galactosylceramide (αGalCer) is known as a potent immune modulator mainly due to NKT cell activation. Using a mouse tetanus toxoid (TT) immunization model, we observed that neonatal mice given αGalCer at the time of primary immunization on day (d) 17 had a significant higher TT-specific IgM response (ELISA), while given αGalCer at d7 during immunization only resulted in a marginal boosting. Consistently, immunostaining of the spleen sections from αGalCer-treated d17 immunized neonates showed higher number of Ki67+ cells in the splenic germinal center area, suggesting stronger response after immunization. In vitro kinetic studies revealed that spleen cells from newborn to d7 neonates did not respond to αGalCer stimulation, whereas cell proliferation was markedly increased by αGalCer after d7, and became dramatic around neonatal d17-18, which was accompanied by increased B and T lymphocyte populations in the spleen. In addition, in d17 spleen cells, αGalCer significantly stimulated the proliferation of CD23+ B cells, a subset of B cells enriched in germinal centers. These data suggest that αGalCer is an effective stimulator of the immune system in late neonatal stage and thus may be useful as a potential adjuvant to achieve an efficient immunization.

Role of Complement Receptor Type 2 and Endogenous Complement in the Humoral Immune Response to Conjugates of Complement C3d and Pneumococcal Serotype 14 Capsular Polysaccharide

Conjugation of the complement fragment C3d to both T-cell-dependent (TD) protein and T-cell-independent type 2 (TI-2) polysaccharide antigens enhances the humoral immune response in mice immunized with either type of antigen. However, the ability of C3d-protein conjugates to enhance the antibody response in mice deficient in complement receptor types 1 and 2 (CR1 and CR2) has raised questions about the role of C3d-CR2 interactions in the adjuvant effect of C3d. In this study, we examined the role of CR2 binding and endogenous complement activation in the antibody response to conjugates of C3d and serotype 14 pneumococcal capsular polysaccharide (PPS14). To block binding of PPS14-C3d conjugates to CR2, mice were immunized with a mixture of vaccine and (CR2)2-immunoglobulin G1 (IgG1). Mice receiving (CR2)2-IgG1 at the time of primary immunization had a marked reduction in the primary anti-PPS14 antibody response but an enhanced secondary anti-PPS14 response, suggesting that C3d-CR2 interactions are required for the primary response but can have negative effects on the memory response. Further, compared with mice receiving PPS14-C3d having a high C3d/PPS14 ratio, mice immunized with PPS14-C3d with low C3d/PPS14 ratios had an enhanced secondary antibody response. Treatment of mice with cobra venom factor to deplete complement had insignificant effects on the antibody response to PPS14-C3d. Experiments with CBA/N xid mice confirmed that PPS14-C3d conjugates retain the characteristics of TI-2 rather than TD antigens. Thus, the adjuvant effect of C3d conjugated to PPS14 requires C3d-CR2 interactions, does not require activation of endogenous complement, and is not mediated by TD carrier effects.

Short-term stress experienced at time of immunization induces a long-lasting increase in immunologic memory

It would be extremely beneficial if one could harness natural, endogenous, health-promoting defense mechanisms to fight disease and restore health. The psychophysiological stress response is the most underappreciated of nature's survival mechanisms. We show that acute stress experienced before primary immunization induces a long-lasting increase in immunity. Compared with controls, mice restrained for 2.5 h before primary immunization with keyhole limpet hemocyanin (KLH) show a significantly enhanced immune response when reexposed to KLH 9 mo later. This immunoenhancement is mediated by an increase in numbers of memory and effector helper T cells in sentinel lymph nodes at the time of primary immunization. Further analyses show that the early stress-induced increase in T cell memory may stimulate the robust increase in infiltrating lymphocyte and macrophage numbers observed months later at a novel site of antigen reexposure. Enhanced leukocyte infiltration may be driven by increased levels of the type 1 cytokines, IL-2 and IFN-gamma, and TNF-alpha, observed at the site of antigen reexposure in animals that had been stressed at the time of primary immunization. In contrast, no differences were observed in type 2 cytokines, IL-4 or IL-5. Given the importance of inducing long-lasting increases in immunologic memory during vaccination, we suggest that the neuroendocrine stress response is nature's adjuvant that could be psychologically and/or pharmacologically manipulated to safely increase vaccine efficacy. These studies introduce the novel concept that a psychophysiological stress response is nature's fundamental survival mechanism that could be therapeutically harnessed to augment immune function during vaccination, wound healing, or infection.

Depletion of Complement Has Distinct Effects on the Primary and Secondary Antibody Responses to a Conjugate of Pneumococcal Serotype 14 Capsular Polysaccharide and a T-Cell-Dependent Protein Carrier

Complement activation plays a critical role in the immune response to T-cell-dependent and T-cell-independent antigens. However, the effect of conjugation of T-cell-dependent protein carriers to T-cell-independent type 2 antigens on the requirement for complement in the humoral immune response to such antigens remains unknown. We studied the role of complement activation on the antibody response of BALB/c mice immunized with the T-cell-independent type 2 antigen serotype 14 pneumococcal capsular polysaccharide (PPS14), either in unmodified form or conjugated to ovalbumin (OVA). In mice immunized with either PPS14 or PPS14-OVA, depletion of endogenous complement at the time of primary immunization by treatment with cobra venom factor (CVF) diminished serum anti-PPS14 concentrations after primary immunization but enhanced antibody responses after secondary immunization. The secondary immunoglobulin G (IgG) anti-PPS14 antibody response after immunization with PPS14-OVA was especially enhanced by complement depletion, was observed at doses as low as 0.2 mug of antigen, and was maximal when CVF was administered within 2 days of immunization. The avidity and opsonophagocytic functions of IgG anti-PPS14 antibodies were comparable in mice immunized with PPS14-OVA with or without complement depletion. Serum anti-PPS14 antibody concentrations were near normal, and the enhancing effects of CVF treatment on the secondary anti-PPS14 antibody response were also apparent in splenectomized mice immunized with PPS14-OVA. These results demonstrate that complement activation can have distinct effects on the primary and secondary antibody responses to a T-cell-independent type 2 antigen, either unmodified or conjugated to a T-cell-dependent protein carrier. These differences should be taken into consideration when using complement to modulate the immune response to vaccines.

Maternal immunization with Haemophilus influenzae type b vaccines in different populations

Haemophilus influenzae type b (Hib) vaccines provide an excellent model for maternal immunization because effective vaccines are readily available and the vaccines are safe and reliable, and markers of efficacy have been established and standardized. Studies of polysaccharide and conjugate Hib vaccines administered to pregnant women and women of childbearing ages are reviewed in this paper. The type of vaccine has been shown to be important in increasing transplacental passage of maternal antibody. The timing of vaccine during pregnancy is also important in the transfer of this antibody. The total amount of IgG antibody in the mother, as well as the isotype class and subclass of IgG antibody, influences the final levels of antibody in the neonate. Placental integrity has been shown to be important in the active transport of antibody from mother to fetus. The impact of increased levels of Hib antibody in infants at the time of primary immunization with Hib does not appear to interfere with vaccine efficacy, although higher antibody levels in infants at the time of immunization may result in lower total antibody levels following all doses of vaccine. Principles observed in these studies have potential application against other important neonatal pathogens.

Endogenous pro- and anti-inflammatory cytokines differentially regulate an in vivo humoral response to Streptococcus pneumoniae.

Proinflammatory cytokines play a critical role in innate host defense against extracellular bacteria. However, little is known regarding the effects of these cytokines on the adaptive humoral response. Mice injected with a neutralizing anti-tumor necrosis factor alpha (TNF-alpha) monoclonal antibody (MAb) at the time of primary immunization with intact Streptococcus pneumoniae (strain R36A) showed a substantial reduction in both the primary immunoglobulin G (IgG) response specific for the cell wall protein, pneumococcal surface protein A (PspA), as well as in the development of PspA-specific memory. In contrast, anti-TNF-alpha MAb injected only at the time of secondary immunization with R36A failed to alter the boosted anti-PspA response. TNF-alpha was required only within the first 48 to 72 h after primary immunization with R36A and was induced both by non-B and non-T cells and by lymphoid cells, within 2 to 6 h after immunization, with levels returning to normal by 24 h. Thus, the early innate release of TNF-alpha was critical for optimal stimulation of the subsequent adaptive humoral response to R36A. Additional proinflammatory (interleukin 1 [IL-1], IL-6, IL-12, and gamma interferon [IFN-gamma]) as well as anti-inflammatory (IL-4 and IL-10) cytokines were also transiently induced. Mice genetically deficient in IL-6, IFN-gamma, or IL-12 also showed a reduced IgG anti-PspA response of all IgG isotypes. In contrast, IL-4(-/-) and IL-10(-/-) mice immunized with R36A showed a significant elevation in the IgG anti-PspA response, except that there was decreased IgG1 in IL-4(-/-) mice. In this regard, a marked enhancement in the induction of proinflammatory cytokines was observed in the absence of IL-10, relative to controls. Ig isotype titers specific for the phosphorycholine determinant of C-polysaccharide were similarly regulated, but to a much more modest degree. These data suggest that proinflammatory and anti-inflammatory cytokines differentially regulate an in vivo protein- and polysaccharide-specific Ig response to an extracellular bacteria.

Inhibition of murine IgE and immediate cutaneous hypersensitivity responses to ovalbumin by the immunomodulatory agent leflunomide.

Leflunomide has been identified as an immunoregulatory and anti-inflammatory compound. Allergic disease is characterized by elevated serum IgE levels, production of allergen-specific IgE and the release of inflammatory mediators from mast cells and granulocytes. Here we demonstrate, using an in vivo murine model, the ability of leflunomide to down-regulate levels of total and allergen-specific serum IgE production. Mice receiving leflunomide (45 mg/kg) orally at the time of primary immunization with ovalbumin adsorbed to aluminium hydroxide adjuvant, showed a reduction in total serum IgE levels of 95%, 41% and 32% following primary, secondary and tertiary immunizations, respectively (P < 0.05). When leflunomide was administered both at the time of primary and subsequent immunizations, reductions in total and specific serum IgE levels of > 80% and > 38%, respectively, were observed (P < 0.05). Administration of leflunomide to mice which had already developed an IgE response resulted in reductions in total and specific serum IgE levels of > 80% and > 45%, respectively (P < 0.05). Following leflunomide treatment, animals failed to develop immediate cutaneous hypersensitivity responses when challenged intradermally with allergen. Down-regulation of immunoglobulin production was not restricted to IgE, since levels of allergen-specific IgG1 and IgG2a in serum were also reduced. The finding of significant reductions in total and allergen-specific IgM suggests that the mechanism of action does not involve selective inhibition of immunoglobulin class switching. A loss in production of the T helper cell-derived B cell differentiation factor IL-5 may account for the reduction in immunoglobulin levels. In adoptive transfer experiments leflunomide did not induce tolerance in allergen-reactive Th2 populations, contrary to animal disease models of transplantation and autoimmunity, where leflunomide was shown to induce tolerance in the effector T cell population.

Competitive inhibition in vivo and skewing of the T cell repertoire of antigen-specific CTL priming by an anti-peptide-MHC monoclonal antibody.

We have recently described a mAb, KP15, directed against the MHC-I/peptide molecular complex consisting of H-2D(d) and a decamer peptide corresponding to residues 311-320 of the HIV IIIB envelope glycoprotein gp160. When administered at the time of primary immunization with a vaccinia virus vector encoding gp160, the mAb blocks the subsequent appearance of CD8(+) CTL with specificity for the immunodominant Ag, P18-I10, presented by H-2D(d). This inhibition is specific for this particular peptide Ag; another H-2D(d)-restricted gp160 encoded epitope from a different HIV strain is not affected, and an H-2L(d)-restricted epitope encoded by the viral vector is also not affected. Using functional assays and specific immunofluorescent staining with multivalent, labeled H-2D(d)/P18-I10 complexes (tetramers), we have enumerated the effects of blocking of priming on the subsequent appearance, avidity, and TCR Vbeta usage of Ag-specific CTL. Ab blocking skews the proportion of high avidity cells emerging from immunization. Surprisingly, Vbeta7-bearing Ag-specific TCR are predominantly inhibited, while TCR of several other families studied are not affected. The ability of a specific MHC/peptide mAb to inhibit and divert the CD8(+) T cell response holds implications for vaccine design and approaches to modulate the immune response in autoimmunity.

Retinoic acid and polyriboinosinic acid act synergistically to enhance the antibody response to tetanus toxoid during vitamin A deficiency: possible involvement of interleukin-2 receptor-beta, signal transducer and activator of transcription-1, and interferon regulatory factor-1.

Antibody responses to T cell-dependent antigens are reduced during vitamin A (VA) deficiency and restored by retinoids. To test whether retinoic acid (RA) and polyinosinic:polycytidylic acid (PIC), an inducer of interferons, can increase specific antibody production, VA-deficient rats were treated with all-trans-RA, PIC, or both at the time of primary immunization with tetanus toxoid. VA-deficient rats produced low primary and secondary anti-tetanus IgG responses (P<.001 vs. VA-sufficient controls). Both responses were increased synergistically by RA plus PIC (P<.0001). In VA-deficient spleens, mRNAs were low for interleukin (IL)-2 receptor-beta, interferon regulatory factor-1, and signal transducer and activator of transcription 1. Each, however, was induced by RA plus PIC (P<.0001 vs. controls). Conversely, IL-12 and IL-10 mRNAs were elevated in VA deficiency and were induced by PIC and suppressed by RA. Thus, RA plus PIC appears to be a promising combination for stimulating antigen-specific immunity. Several molecular factors identified here may partially account for the observed enhancement.

Effect of long-term immunization against inhibin on sperm output in bulls.

To determine the effect of neutralization of inhibin on sperm output, 12 Holstein bulls were paired by birth date and weight on Day 1 of age. Each bull was actively immunized against bovine inhibin alpha1-26 gly-tyr (bINH) conjugated to human alpha globulin (HAG, n = 6 bulls) or HAG alone (controls, n = 6) at 60 days of age; booster immunizations were administered at 90, 104, 124, 270, and 395 days of age. Body weights and scrotal circumferences were measured at the time of primary immunization and at 10 days after each booster. In addition, jugular blood was obtained at 60, 70, 100, 114, 134, 280, and 405 days of age, during the 3-wk sperm collection period, and during a 6-h blood-sampling period after sperm collection to determine bINH antibody titer and concentrations of FSH, LH, testosterone, and estradiol. Beginning at 405 days of age, sperm output was measured 3 days/wk for 3 wk with two successive ejaculates collected each day for a total of 18 ejaculates per bull. During Days 60-405 of age, the increase in titer of bINH antibodies, scrotal circumference, and serum concentration of FSH was greater (p < 0.01) for the bINH-immunized compared with control bulls. There were significant (p < 0.01) pair x treatment interactions for sperm output and serum FSH and LH concentrations. Specifically, bINH-immunized bulls for four of the six pairs had nearly 50% greater serum FSH concentrations and sperm output. For the remaining two pairs, sperm output was lower and FSH was either lower or only marginally higher in the bINH-immunized bulls compared with controls. Also, the control bulls for the two remaining pairs produced more sperm than all but one bINH-immunized bull, and had markedly higher serum LH concentrations than all other bulls. To summarize, enhancement of sperm output after immunization against inhibin depends on the subsequent increment in FSH concentrations. We conclude that inhibin suppresses spermatogenesis. Thus, methods to immunoneutralize inhibin may have merit as a therapeutic route to enhance sperm production in reproductively maturing bulls.

Enhancement of a secondary antibody response to vesicular stomatitis virus "G" protein by IFN-gamma treatment at primary immunization.

Abstract IFN-gamma is a secreted polypeptide product of stimulated T lymphocytes with immunomodulatory properties as well as antiviral activity. We have investigated the effects of IFN-gamma treatment on a neutralizing antibody response to vesicular stomatitis virus (VSV) when administered in conjunction with immunization using purified envelope glycoprotein "G" of VSV. Administration of rIFN-gamma to mice or cattle at the time of primary immunization with VSV G glycoprotein enhanced the magnitude of a secondary virus-neutralizing antibody response after a booster administration of the same Ag without IFN-gamma treatment. Enhancement was statistically significant and occurred at relatively low doses of IFN-gamma in the absence of any additional adjuvants. Furthermore, cattle treated with IFN-gamma at the time of a single primary immunization were more resistant to VSV challenge than those immunized without IFN-gamma treatment. IFN-gamma treatment in conjunction with a single primary immunization may therefore provide a practical means of enhancing protection from a viral challenge without the use of inflammatory adjuvants or booster immunizations.

B lymphocyte regulation of the immune system. I. In vivo biologic activity of the novel lymphokine, B cell-derived enhancing factor (BEF).

B cell-derived enhancing factor (BEF) is a lymphokine of B cell origin which was originally identified and characterized by its ability to enhance in vitro antibody responses, an effect shown to be due to the ability of BEF to reduce the activation of suppressor T cells. The present study was undertaken to determine whether BEF could also be active in modulating antibody responses in vivo. The data presented here demonstrate that BEF is biologically active in vivo, as manifested by significantly enhanced primary IgM and IgG antibody responses in mice that were either injected with BEF prepared exogenously or implanted with growing BEF-secreting cells of a B cell line. Moreover, BEF was shown to enhance subsequent development of immunologic memory in mice pretreated with BEF at the time of primary immunization; these mice then displayed enhanced secondary responses when challenged with the same antigen some weeks later. The mechanism by which BEF exerts biologic activities to positively modulate in vivo antibody responses and immunologic memory reflects the ability of BEF to modulate one or more T cell functions, as evidenced by the following findings. 1) Transient in vitro exposure to BEF of T cells, but not of B cells, endowed such cells with the capacity to adoptively transfer enhanced primary antibody responses to irradiated recipients. 2) Utilizing adoptive in vivo antibody responses, in which fractionated B cell or T cell populations were obtained from BEF-pretreated mice, revealed that one effect of BEF which results in enhanced immunologic memory is related to its activity on T cells during the priming phase of the immune response. Finally, the existence of this B cell-derived lymphokine and the demonstration of its in vivo regulatory effects on the immune system provide yet another example of the emerging biologic importance of B lymphocytes in the overall regulation of the immune system.

Immunomodulating effects of 13-cis-Retinoic acid on the IgE response of BALB/c mice.

The results reported here are an extension of our previously reported studies on the adjuvant effects of 13-cis-retinoic acid (13-cRA). Previous results, as well as those reported herein, show the lack of a primary IgE response with elevated and sustained secondary IgE responses in animals treated with 13-cRA. It was determined that this lack of a primary IgE response was not due to overt immunotoxicity by 13-cRA, suggesting that 13-cRA is priming a population of memory cells; however, either the formation of suppressor cells or the lack of an appropriate stimulus at the time of primary immunization also prevented a demonstrable primary IgE antibody response. It was also demonstrated that the absence of a primary response was not due to a sensitivity of the immune system to the timing of the administration of 13-cRA relative to immunization, as all animals given 13-cRA at either day -2, -1, 0, 1, 2 or 3 relative to primary immunization showed no primary response but high secondary IgE responses. These experiments, which closely mimic the clinical treatment regimen, indicate that patients receiving retinoid therapy should be closely monitored for immunological side effects, such as immediate hypersensitivity to environmental allergens.

Regulation of IgE Antibody Production by Serum Molecules

Abstract Exposure of mice to low doses of ionizing x-irradiation at or near the time of primary immunization with 2,4-dinitrophenyl (DNP)-Ascaris suum extract (ASC) results in substantial enhancement of IgE anti-DNP antibody responses; the IgG antibody responses of such mice do not increase after such manipulations. This selective enhancement of IgE antibody production occurs in mice of both high and low IgE responder phenotype, although the extent of enhancement compared to unmanipulated control animals is more striking in low IgE responder mice. The studies presented here demonstrate that the irradiation-enhanced IgE antibody responses of low responder SJL and C57BL/6 mice as well as of intermediate responder AKR mice can be effectively suppressed by passive transfer of CFA-immune serum obtained from isologous donor mice. Moreover, adoptive secondary IgE antibody responses in SJL recipients of primed syngeneic spleen cells can be totally abolished by passive transfer of CFA-immune serum or ascitic fluid from CFA-immune mice. The suppressive activity of CFA-immune serum can be diminished or eliminated by exposure of CFA-primed donor mice to low dose x-irradiation at an appropriate point during the priming regimen, after a single inoculation of CFA, and before collection of serum. Low dose x-irradiation was not effective in eliminating suppressive activity of CFA-induced ascites fluid obtained from donor mice inoculated repeatedly with CFA. In contrast to the capacity of CFA-immune serum from isologous donors to suppress irradiation-enhanced IgE responses of low responder mice, similar sera or ascites fluids were ineffective in suppressing irradiation-enhanced responses of high responder BALB/c or (SJL × BALB/c)F1 hybrid mice. This was true irrespective of whether such sera or ascites were obtained from isologous donors or from donor mice of the low IgE responder phenotype. The implications of these findings with respect to clarifying some of the previously confusing observations concerning 1) the effects of adjuvant administration on IgE antibody production, and 2) differences in the capacities of different mouse strains to produce IgE antibodies in high vs low quantities are discussed.

Mechanism of adjuvant activity of poly A:U on antibody responses to hapten-carrier conjugates

The adjuvant action of poly A:U has been analyzed in a system measuring humoral immune responses to hapten-carrier conjugates in mice. Administration of poly A:U at the time of primary immunization with 2,4-dinitrophenyl (DNP)-keyhole limpet hemocyanin (KLH) shortens the induction period for, and heightens the magnitude of peak anti-DNP antibody and specific memory cell production. In order to define the cellular locus of poly A:U action, the effect of this adjuvant on adoptive secondary anti-DNP antibody responses was studied. Spleen cells from DNP-KLH-primed donors, which normally fail to develop adoptive secondary anti-DNP responses to a heterologous conjugate such as DNP-bovine gamma globulin (BGG), can be stimulated to do so when an appropriate dose of poly A:U is administered with DNP-BGG. The capacity for poly A:U to exert this effect requires the presence of T lymphocytes, since depletion of such cells by treatment of the donor cell inoculum with anti-θ serum and complement in vitro prior to adoptive transfer abrogates the response to DNP-BGG plus poly A:U. Moreover, evidence is presented that demonstrates that poly A:U exerts its adjuvant action on the small number of unimmunized BGG-specific T lymphocytes in the donor cell inoculum. This conclusion derives from the failure of poly A:U to augment adoptive secondary anti-DNP responses to the DNP derivative of a nonimmunogenic copolymer of d-glutamic acid and d-lysine ( d-GL) for which there are few or no specific, functional T cells.

Secondary Antibody-Forming Potential of Aged Mice, with Special Reference to the Influence of Adjuvant on Priming

Aged (20 months old) NMRI mice, showing a significantly reduced primary immune response to 4 × 10&lt;sup&gt;8&lt;/sup&gt; sheep erythrocytes (SE), reacted to a secondary injection of 4 × 10&lt;sup&gt;8&lt;/sup&gt; SE 1 month after primary immunization with a typical secondary immune response at both the adjuvant cellular and humoral levels. This specific anamnestic response was not found to be diminished, as compared to that of young adult controls (3 months old at the time of primary immunization). When killed cells of &lt;i&gt;Bordetella pertussis&lt;/i&gt; were given as an adjuvant together with the primarily injected erythrocyte antigen, the process of priming for the secondary immune response was found to be significantly increased in both the aged and the young adult animals. The impressive restoration of the antibody-forming potential observed following secondary antigenic stimulation was associated with a remarkable restoration of the splenic structure. Splenic amyloidosis did not impair the secondary antibody-forming potential to a significant extent. It is suggested that the suppressed immunological reactivity of aged mice to a primary antigenic stimulus is mainly due to deficiencies in the regulatory factors, such as antigen-processing and antigenic triggering of immunocompetent precursor cells.

Studies on Heterologous Antilymphocyte and Antithymocyte Sera

Summary The effects of rabbit antilymphocyte (ALS) and antithymocyte (ATS) sera on the early primary and secondary response of mice to sheep RBC were studied using the hemolytic plaque technique as an assay system for enumerating antibody-producing cells. Immunosuppressive effectiveness was related to the routes of immunization and serum treatment. Intraperitoneal administration of ALS or ATS was the most effective in reducing the number of splenic plaque-forming cells (PFC), and intravenous administration was the least effective when associated with i.p. immunization. Mice treated successively on days -1, 0 and +1 with 0.25 ml of ALS or ATS had a peak response of 4000 PFC by 76 hr following primary immunization compared to 387,000 for nontreated controls at 96 hr. There was a prolongation of the lag phase and a truncation of the exponential phase which may have been due to a reduction in the number of stimulated antigen sensitive precursor cells. Mice treated with ALS or ATS at the time of primary immunization had a reduction in both unfacilitated and facilitated splenic PFC 3 days following a second injection of SRBC. Serum hemagglutinin and hemolysin titers were identical to controls, and it was suggested that peritoneal lymph nodes may have compensated for the decreased splenic response. Infusion of ALS-treated and immunized mice with 50 × 106 spleen cells from normal syngeneic donors resulted in some restoration of immunocompetence both in terms of splenic PFC and serum antibodies.