Specific Plaque-forming Cells Research Articles

The influence of vehicle gavage on seasonality of immune system parameters in the B6C3F1 mouse.

Seasonal hyporesponsiveness and other immune system variations were observed in female B6C3F1 mice during routine screening tests for immunomodulation. In a retrospective assessment, 4 years of data from over 1200 naive, vehicle, and immunosuppressed (cyclophosphamide-treated) control mice were compiled and analyzed for uniformity and significant circannual pattern of immune response. Endpoints included body, spleen, and thymus weights and an immunotoxicity assessment which enumerates specific antibody plaque-forming cells (PFC) in the spleen following immunization with sheep red blood cells. Dosing vehicles were water, corn oil, or 1% methyl cellulose instilled by oral gavage in a 5-20 ml/kg volume once daily for 5 days. Four days later, terminal organ and body weights were recorded and PFC were quantitated. Upon analysis, individual datapoints were arrayed in consistent circannual and seasonal patterns. In naive mice, the yearly peak response in circannual rhythm (acrophase) for body weight and PFC parameters occurred in the summer, with acrophases for spleen and thymus weights located in the spring. Vehicle gavage modulated the circannual/seasonal means and acrophases of all measured endpoints in distinct patterns which varied by vehicle. Body weight was the endpoint least affected by vehicle treatment. Corn oil was the vehicle resulting in the most dramatic effects on natural rhythm. As expected, the naive mice receiving an ip injection of cyclophosphamide exhibited significant decreases (p </= 0.05) in circannual mean values for PFC response and relative organ weights when compared to naive controls and the elimination of significant expression of rhythm for PFC parameters. Our results indicate that dosing vehicles alter normal seasonal patterns of biological responses in the mouse. These effects on natural rhythms should be considered in toxicity evaluations, especially when comparing datapoints collected at different times of the year.

Kinetics of phagocytic activity, plaque-forming cells and specific agglutinins of turbot (Scophthalmus maximus L.) immunised with O antigen of Vibrio damsela and Pasteurella piscicida

The O antigens derived from Vibrio damsela and Pasteurella piscicida were evaluated to determine their ability to enhance non-specific defence mechanisms and the specific immune response in turbot. Intraperitoneal injections of 100 μg V. damsela or P. piscicida O antigen resulted in an increased phagocytic activity of splenic leucocytes 3 days after immunisation, although the level of phagocytosis of sheep red blood cells (SRBC) was always low. In both groups of immunised fish a peak in the specific plaque-forming cells (PFC) was observed 21 days post-injection. There were no differences in PFC number induced by the two bacterins in turbot. Peak antibody titres were 28 and 42 days after immunisation with O antigen from P. piscicida and V. damsela respectively.

Immunotoxicological evaluation of toluene exposure via drinking water in mice

Toluene is a known contaminant found in trace amounts in groundwater. Male CD-1 mice were exposed to 0, 17, 80, and 405 mg/liter toluene in drinking water for 4 weeks. Immune function assays were selected to evaluate specific humoral and cell-mediated immunity, interleukin-2 (IL-2) activity, hematology, along with general toxicity. Toluene produced an increase in liver weight and decrease in thymus mass at the highest dose. No effects on body weights and hematological parameters, including erythrocytes, leukocytes, and their differentials were noticed. Mitogenesis by lipopolysaccharide, pokeweed mitogen, concanavalin A, and phytohemagglutinin were suppressed in splenocytes from treated mice. Splenocyte lymphoproliferation to alloantigens decreased at the 405 mg/liter concentration only. Numbers of sheep red blood cell (SRBC)-specific plaque-forming cells decreased in the highest dosed animals; however, no significant change was observed in the serum alpha-SRBC antibody level. Toluene also adversely affected IL-2 synthesis at the 405 mg/liter concentration. Findings suggest that alteration of immune functions of mice ingesting toluene was generally evident at relatively high doses, except for splenic lymphocyte responses to selected mitogens.

Regulation of idiotope expression. III. H-2 influences the magnitude and the idiotypy of a T-independent antibody response in mice of certain genetic backgrounds.

Antibody response to the phosphocholine (PC) epitope on Streptococcus pneumoniae R36a (Pn), a T-independent Ag type 2, was studied in H-2 congenic mouse strains. The PC-specific antibody plaque-forming cells (PFC) were enumerated in the spleen at various intervals after the primary Pn injection, and the proportion of PFC that produced antibody expressing the AB1-2 idiotope (Id) was determined by using the corresponding monoclonal anti-Id. AB1-2 is a cross-reactive Id, detectable on germline-encoded PC antibody of the T15 family, and on most, but not all, somatic variants of that antibody. The specific PFC responses in BALB/c (H-2d) and BALB.B (H-2b) strains were of comparable magnitude and most, if not all, PFC were ABl-1 Id-positive (AB1-2+). This was not the case in the responses of the B10D2 (H-2d) vs C57BL/10 (H-2b) strains and the D1.C (H-2d) vs D1.LP (H-2b) strains (on DBA/1 background). In each of these pairs, the H-2d mice were high responders, and the response was dominated by AB1-2 Id (greater than or equal to 80% AB1-2+ PFC at the peak, on day 5). The H-2b mice were low responders, and only a minor proportion of PFC (less than or equal to 30%) were AB1-2+; an increase of AB1-2+ was seen later in the response (d.10). The results of PFC assays were confirmed by measuring the PC-binding antibody and AB1-2 Id in the sera of D1.C and D1.LP mice immunized repeatedly with Pn. Moreover, D1.LP mice that had very low levels of AB1-2 Id had higher serum levels of antibody expressing two other T15 Id, B36-82, and B24-44. The B36-82 and B24-44 Id have been previously found on somatic variants of PC antibody expressed independently of the Ab1-2 Id. The concentrations of these two Id in D1.LP mice after repeated immunization approached those in D1.C. These results indicate that 1) the H-2 allelism may have a significant effect on TID antibody response in mice of a certain genetic background, but not in the BALB/c; and 2) the idiotypic repertoire of the response may be influenced by H-2 at the level of clonal variants of PC-reactive cells.

Improved plaque production for short-term bone marrow and fetal liver cultures

The addition of 0.5% globulin-free (GF-BSA) or 0.5% delipidated BSA (D-BSA)to short-term murine bone marrow (BM) (cultures) increased the number of plaque-forming cells (PFC) responding to trinitrophenylated lipopolysaccharide (TNP-LPS) 2–5-fold 1.1 × 10 4−2.7 × 10 4 PFC per 10 × 10 6 nucleated BM cells. Although it was necessary to continue to supplement these cultures with 5% fetal calf serum (FCS), the inclusion of the aforementioned BSA preparations provided enhanced PFC production for all lots of FCS tested. Similarly, these preparations of BSA made it feasible to also culture BM in autologous mouse sera (MS) or in medium without 2-mercaptoethanol (2-ME) if in the latter case the D-BSA was pretreated with 2-ME. Thus, the inclusion of GF-BSA or D-BSA in short term cultures of BM not only substantially increased the number of Ig-secreting B cells produced in response to TNP-LPS but seemed to eliminated the need to screen for supportive batches of FCS or MS. These preparations of BSA also facilitated hapten specific PFC responses of fetal liver cultures.

Correlation between specific immunosuppression and polyclonal B cell activation induced by a protein secreted by Streptococcus mutans.

The relationship between polyclonal B cell activation and immunosuppressor effects induced by F5'EP-Sm, a non-cytotoxic protein secreted by Streptococcus mutans, was studied in C57BL/6 mice. Mice treated with F5'EP-Sm exhibited a considerable increase in splenic nonspecific Ig plaque-forming cells (PFC) compared with untreated mice. The isotypic pattern of non-specific PFC responses favours IgG2a approximately equal to IgG2b greater than IgG3 greater than IgG1 approximately equal to IgM, when taken as a ratio between treated and untreated animals. When F5'EP-Sm was administered 2 days before immunization with sheep red blood cells (SRBC), the non-specific PFC production was accompanied by an ephemeral increase in specific PFC against SRBC 1 day after immunization, which was quickly replaced by a strong immunosuppression. In contrast, when F5'EP-Sm was injected after priming, there was little or no demonstrable suppression of specific PFC, and the increase of non-specific PFC was much less evident. The kinetic curves representing increase or decrease in relation to controls of specific and non-specific PFC are almost mirror images in each of the isotypes. The in vivo suppressor effect was abrogated in thymectomized mice, although the involvement of the T cell compartment is probably secondary to the B cell mitogen effect, since T-depleted spleen cells proliferate and synthesize non-specific Ig when stimulated in vitro with F5'EP-Sm.

Subclinical effects of groundwater contaminants. I: Alteration of humoral and cellular immunity by benzene in CD-1 mice.

Benzene is a known contaminant found in trace amounts in ground water. It has long been associated with myelotoxicity and associated immunologic effects. The present study concerned the immunotoxic potential of benzene following four weeks of continuous oral administration via drinking water at concentrations of 0, 31, 166 and 790 mg/L. Benzene-treated water produced a dose-related decrease in spleen weight and increase in kidney weight; both were significantly different at the highest level. Benzene exposure caused a significant dose-response reduction of peripheral blood leukocytes, lymphocytes, erythrocytes and resulted in a severe macrocytic anemia. Splenic lymphocyte proliferation to both B cell and T cell mitogens [lipopolysaccharide (LPS), pokeweed mitogen (PWM), concanavalin A (Con A) and phytohemagglutinin (PHA)] was followed by a dose-related biphasic responsiveness, enhanced at the lowest dose (31 mg/L) and depressed in the higher dosage groups (166 and 790 mg/L). Cell-mediated immunity as measured by mixed-lymphocyte culture (MLC) response to allogeneic cells and cytotoxic T lymphocyte (CTL) activity to YAC-1 tumor ceils exhibited similar biphasic phenomenon. Antibody production as assessed by enumeration of the sheep red blood cell (SRBC)-specific plaque-forming cells (PFC) indicated a significant suppression of PFC in animals exposed to 166 and 790 mg/L benzene. A decrease in the α-SRBC-antibody titer corresponded to the numbers of PFC. The findings suggest that oral ingestion of benzene, at the concentrations utilized, produced a biologically significant immunotoxic effect on both the humoral and cellular immune responses.

Immunoregulation in the Peyer's patch microenvironment. Cellular basis for the enhanced responses by the B cells of X-linked immunodeficient CBA/N mice.

The Peyer's patches (PP) of X-linked immunodeficient (xid) CBA/N and hemizygous (CBA/N X DBA/2)F1 (CDF1) male mice contain a B cell subpopulation that expresses the Lyb-5 maturational marker and is responsive to type 2 and T cell-dependent antigens in vitro, a B cell phenotype which is absent from the spleens of xid mice. Experiments reported here show that xid spleen B cells co-cultured with B cell-depleted PP cells from xid mice differentiated into specific plaque-forming cells in response to trinitrophenyl-Ficoll (type 2) and sheep erythrocytes (T cell-dependent). Two cell types were involved in this normalization of xid B cell responses. An accessory cell activity present in the PP, but not the spleens, of both CDF1 male (xid) and CDF1 female (normal) mice was required for the response to either the type 2 or T cell-dependent antigens. In the presence of this PP accessory cell, T cells from the PP of either xid or normal mice supported responses to both classes of antigens. In contrast, T cells from the spleens of xid mice did not support the response to trinitrophenyl-Ficoll, although the splenic T cells from normal mice did synergize with PP accessory cells in allowing plaque-forming cell development by xid B cells to this type 2 antigen. The xid PP T cell activity required for the type 2 response by xid B cells was present in the Ly-1+, Lyt-2- subpopulation, and the xid PP accessory cell activity was provided by an enriched population of dendritic accessory cells. These results demonstrate the the lymphoreticular cells comprising the PP microenvironment provide effective support for the differentiation of xid B cells in response to type 2 and T cell-dependent antigens.

Dietary Fatty Acid Modulation of Murine B-Cell Responsiveness

These studies were designed to determine how dietary fat concentration and degree of saturation influence antibody response to a T-dependent antigen. In vivo fatty acid manipulation did not affect the total number of nucleated spleen cells or IgM or IgG-bearing cells. After primary immunization with sheep red blood cells (SRBC), the number of splenic IgM and IgG antigen specific plaque-forming cells (PFC) was lower in mice fed a diet containing a high level of polyunsaturated fat (PUF, safflower oil) than in mice fed a diet containing minimal essential fatty acids (EFA, 0.5% corn oil). Mice fed a high level of saturated fat (SF, coconut oil) exhibited greater IgM PFC responses than the control. After secondary immunization, the number of IgG-producing cells followed a similar response pattern. These differences were also reflected in the serum anti-SRBC IgM and IgG levels as determined by solid-phase radioimmunoassay. Although the level of linoleic acid in whole lymphocytes has been previously reported to change in direct relation to the serum fatty acid level, no differences in the fatty acid composition of isolated lymphocyte plasmalemma were observed. Thus, changes in the number of antibody-forming cells appear to be inversely related to the levels of linoleic acid in other cell compartments. Fluorescence polarization measurements of the lipopholic probe, 1, 6-diphenyl-1,3,5-hexatriene (DPH), in the purified lymphocyte plasmalemma from mice fed a diet high in PUF indicated an increase in mobility. Polarization values for lymphocyte plasmalemmas from mice receiving diets high in SF were not significantly different from the controls. We conclude that dietary fat modulation of splenic B-cell responses was manifested through changes in the number of cells producing antibody and level of antibody produced, not through total splenic B-cell numbers. This B-cell response can be modified, depending upon the fatty acids available to the cell, and may be related to differential effects upon plasma membrane structure.

Effects of prolonged inhalation of silica and olivine dusts on immune functions in the mouse

Immunologic responses were determined in Balb c mice following intermittent silica or olivine inhalations for 150, 300, or 570 days. Animals dust-exposed for 570 days were tested immediately postexposure, while those exposed for 150 or 300 days were tested immediately or were rested for 30 or 150 days as a measure of possible recovery from effects of the dust inhalations. Silica inhalation suppressed the number of specific plaque-forming cells (PFC) in the spleen produced in response to aerosolized Escherichia coli bacteria. When tested after 570 days, silica inhalation also reduced the ability of alveolar macrophages to phagocytize Staphylococcus aureus in vitro. Olivine inhalation also suppressed splenic PFCs and alveolar macrophage phagocytosis, but to a lesser degree than silica. In animals tested after 570 days of dust exposure, it was determined that the ability to lyse allogeneic tumor cells in vitro was impaired by olivine slightly more than by silica, while antibody-dependent cell-mediated cytotoxic and mitogenic responses by splenic lymphocytes were unchanged by inhalation of either dust. The effects of increased exposure periods, and of recovery periods after exposure, were confounded by age-related immunologic changes which were present after the longer exposures.

Effects of the methanol extraction residue (MER) tubercle bacillus fraction on the production of antibodies in vitro: III. Consequence of prior sensitization to MER

Mice repeatedly immunized with the methanol extraction residue fraction of tubercle bacilli (MER) in incomplete Freund's adjuvant produced high titers of circulating antibodies against MER, as assessed by the enzyme-linked immunosorbent assay (ELISA) method. Spleen cells derived from these animals failed to respond to the usual nonspecific immunopotentiating influence of MER on the primary production of antibodies (generation of specific plaqueforming cells) in vitro to sheep red blood cells. The defect was expressed by B lymphocytes and splenic macrophages, but not by splenic T lymphocytes or peritoneal exudate macrophagic cells. Impaired responsiveness by spleen cells from MER-immunized animals to nonspecific immunostimulation was also expressed with regard to another, unrelated biological response modifier, lipopolysaccharide. There was no impairment of responsiveness to polyclonal mitogenic stimulation. Possible mechanisms of the effects described are discussed.

Selective effect of irradiation on responses to thymus-independent antigen.

Low doses of ionizing radiation have a selective immunosuppressive effect on in vivo B cell responses to thymus-independent (TI) antigens. The B cell response, assayed as direct anti-trinitrophenyl (TNP)-specific plaque-forming cells (PFC), induced by type 2, TI antigens (TNP-Ficoll or TNP-Dextran), was reduced, on the average, by 10-fold in animals exposed to 200 rad of ionizing radiation 24 hr before antigen challenge. In contrast, PFC responses to type 1, TI antigens (TNP-lipopolysaccharide or TNP-Brucella abortus) are unaffected in mice exposed to the same dose of radiation. Adoptive transfers showed that this selective immunosuppression is a result of the specific inactivation of the B cell subpopulation responding to type 2, TI antigens. These experiments suggest that physiologic differences exist in the B cell subpopulations of normal mice which respond to type 1, or type 2, TI antigens.

Effect of Maternal Antigenic Stimulation on the Active Immune Responses of Their Offspring

Pregnant mice were stimulated by heterologous erythrocyte and protein antigen, and the active immune responses of their offspring as measured by plaque-forming cells (PFC) were investigated. In offspring derived from mothers immunized by a suitable amount of T-dependent antigen, clear-cut suppression of development of specific PFC in spleen was observed over a significant period after delivery. The mechanism of this suppression was investigated, and the following results were obtained. When the heterologous erythrocyte was used as antigen, the more the specific PFC developed in the mother spleen, the stronger the suppression of PFC observed in their offspring. However, it is worthy of note that passive administration of antibody to pregnant mice did not induce suppression in their young. In case of the protein antigen ovalbumin (OVA), pregnant mice had to be injected with a suitable amount of antigen, along with aluminium hydroxide, for either primary or secondary stimulus to induce the suppression of specific PFC in their offspring. Soluble OVA administered to pregnant mice was not effective for inducing suppression in the offspring. Based on these results, some possible mechanisms are discussed concerning specific PFC suppression in the offspring when pregnant mice are stimulated.

Effects of the methanol extract residue (MER) tubercle bacillus fraction on the production of antibodies in vitro: II. Effects on macrophage and lymphocyte populations

The effect of the methanol extract residue (MER) fraction of BCG tubercle bacilli on the generation of primary antibody responsiveness in vitro to sheep red blood cells (SRBC) was ascertained in cell reconstitution experiments, employing enriched populations of mouse macrophages and of T and B lymphocytes. In each of the antibody generation cultures one or another of the cell fractions had been exposed to MER, either by treatment of the donor animals or by preincubation with the agent for 48 hr in vitro. In some experiments, supernatants of MER-preincubated cells were employed in place of the cells. Macrophages and T cells that had been exposed to MER in vivo or in vitro and their supernatants demonstrated a markedly greater effect than nonexposed cells in the generation of direct specific plaque-forming cells (PFC) upon antigenic stimulation of the cultures with SRBC. In contrast, PFC production was not stimulated in B-lymphocyte populations that had been in contact with the agent.

Human thymus-independent antibody response in vitro: III. Precursor frequencies and fine specificity of human B cells stimulated by TNP-Ba in the presence and absence of Con A

Previously, we reported that human B lymphocytes can be stimulated by trinitrophenylated Brucella abortus (TNP-Ba) in vitro to generate T-independent (TI) hapten specific plaque-forming cells (PFC). Furthermore we showed that addition of Con A on Day 3 of culture enhanced the anti-TNP response. In this report the characteristics of the anti-TNP PFC responses elicited by TNP-Ba in the presence or absence of Con A were further defined by estimating precursor frequencies and clone sizes, and by assessing the diversity of the anti-TNP-PFC response using hapten inhibition profiles. Addition of Con A to TNP-Ba-stimulated cultures was associated with a 2.3- to 3.6-fold increase in anti-TNP precursors and was also accompanied by a more vigorous clonal expansion. Fine specificity analysis of anti-TNP PFC revealed that Con A addition resulted in PFC with unique hapten inhibition profiles in that they were less inhibitable by TNP-EACA, TNP-lysine, and DNP-lysine but more inhibitable by DNP-glycine when compared to PFC generated by TNP-Ba alone. These findings suggest that at least some of the additional precursors recruited in the presence of Con A are qualitatively distinct from those activated by TNP-Ba alone since they express different V region gene products.

Immune response to bacterial dextrans. II. T cell control of antibody isotypes.

The isotype distribution of Dextran B 512 (Dex)-specific plaque-forming cells (PFC) and serum antibodies was studied after in vivo immunization in C57BL/6 mice. Although IgG2b and IgG3 could also be detected in most individuals, the majority of non-IgM PFC were of the IgA isotype. All classes other than IgM were T cell-dependent, as shown by their complete absence in athymic "nude" mice. This unusual isotype pattern was further investigated by studying the antibody responses to the same Dex epitope coupled to a protein carrier, and to a different hapten coupled to the carrier Dex or to a protein. The results show that IgA responses are epitope-related and selectively associated with anti-Dex antibodies: no IgA PFC are detected against a hapten coupled to Dex or proteins, while the enhanced levels of helper cell reactivity provided by protein carrier to Dex result in the appearance of IgG1 antibodies in addition to IgA. These results indicate that T cells that modulate isotype patterns in these responses can discriminate between Dex- and DNP-specific B cells in the response to the same carrier. Since the same idiotype is detected on a large fraction of the IgM and IgA anti-Dex response and antiidiotypic helper cells have previously been detected in normal C57BL/6 mice, we suggest that idiotype-specific T cells control the production of IgA antibodies upon immunization with Dex.

T cell-replacing activity of C8-derivatized guanine ribonucleosides.

The capacity of the C8-substituted guanine ribonucleosides to provide T cell-like signals to cultures of splenic B cells was evaluated. We showed previously that these low m.w. nucleoside derivatives traverse the cell membrane and induce their effects from an intracellular location. The current studies clearly demonstrate that 8 mercaptoguanosine (8MGuo), when added to cultures of B cells and macrophages in the presence of antigen, is capable of supplying a "second signal" for B cells, enabling them to generate high numbers of specific plaque-forming cells against the immunizing antigen. This effect is duplicated in cultures of spleen cells from congenitally athymic mice. Inhibition of interleukin 2 (IL 2) generation by cyclosporin A, such that the antibody response of normal spleen cells is entirely abrogated, has minimal effects on the T cell-replacing activity of 8MGuo. Additivity studies with MLC supernatants as well as kinetic analyses with IL 2-associated lymphokines substantiate that these factors act by a mechanism distinct from that of 8MGuo and 8BrGuo. These observations establish these nucleoside activators as exciting new probes for T helper cell activity and an effective non-T cell source of T cell-like signals.

Activation of human B lymphocytes after immunization with pneumococcal polysaccharides.

The in vivo and in vitro immune response after in vivo immunization with pneumococcal polysaccharides (PPS) has been analyzed in man. Substantial differences were noted in this system when compared with human responses to soluble protein antigens. Within 6 d after immunization, specific PPS antigen-binding cells (ABC), specific plaque-forming cells (PFC), and cells capable of spontaneously synthesizing in vitro large amounts of specific anti-PPS immunoglobulin (Ig) G. IgA, and lesser amounts of specific IgM appeared in the peripheral blood. The ABC, PFC, and the total amount of specific spontaneous antibody production followed nearly identical kinetics after immunization. Low doses of irradiation markedly inhibited spontaneous anti-PPS antibody production by lymphocytes obtained 7 or 8 d after immunization, suggesting a requirement for in vitro proliferation for full expression of antibody-secreting capability of these cells that are activated in vivo and are capable of spontaneous antibody production in vitro. Spontaneous secretion by B lymphocytes in vitro was independent of T cells, unmodified by the addition of T cell factors, and readily suppressible by pokeweed mitogen (PWM). By 2 wk after immunization, spontaneous anti-PPS antibody production in vitro was no longer detected. Subsequent stimulation of lymphocytes in culture with a wide range of concentrations of specific antigen did not trigger either proliferation or specific antibody synthesis. Despite the unresponsiveness of these cells to antigenic stimulation at this time, they were capable of specific antiPPS antibody production after stimulation with PWM. In vivo booster immunization 4 mo after an initial immunization did not reproduce the increased numbers of ABC, PFC, or in vitro specific antibody production that had been found 4 mo earlier. The dichotomy in capacity for activation of PPS-specific B cells by PWM vs. specific antigen, and the in vivo and in vitro unresponsiveness to in vivo booster immunization with PPS, contrast sharply with previous studies in man with soluble protein antigens such as keyhole limpet hemocyanin and tetanus toxoid. Furthermore, the lack of T cell activation by PPS also contrasts with previous results with tetanus toxoid and other protein antigens. This system should prove useful in delineating certain aspects of human B cell physiology not readily approachable with standard soluble protein antigens.

Use of plaque assays to study thyroglobulin autoantibody synthesis by human peripheral blood lymphocytes.

Plaque assays have been used to study thyroglobulin autoantibody synthesis and total immunoglobulin production by cultures of peripheral blood lymphocytes from patients with Hashimoto's thyroiditis. Freshly isolated Hashimoto or normal lymphocytes contained small numbers (7-1300) of total IgG plaque-forming cells (PFC) and total IgM PFC, but specific thyroglobulin antibody PFC was undetectable. After 5-8 days' culture with pokeweek mitogen (PWM), total IgG and IgM PFC were markedly increased to a geometric mean of 10,140 (8414-12,220) IgG PFC and 3450 (163-7534) IgM PFC per 10(6) cultured lymphocytes (95% confidence limits in parentheses). Furthermore, a mean of 63 (22-287) specific IgG thyroglobulin antibody PFC per 10(6) lymphocytes were detectable in cultures of Hashimoto lymphocytes. The IgG thyroglobulin antibody PFC were stimulated by Epstein-Barr virus (EBV) infection, suggesting that EBV infection may be useful in obtaining monoclonal thyroid autoantibodies.

Induction of IgM immunological memory to lipoteichoic acids in rabbits. Part I.

Intravenous immunisation of rabbits with 10(9) lactobacillus fermentum cells elicited a response, specific for lipoteichoic acid (LTA), detectable as IgM plaque-forming cells (PFC) in the spleen by day 2 and as thiol-sensitive 19s antibodies in sera by day 3. Direct PFC responses peaked at day 6, with no indirect PFC demonstrable at the time. Specific IgG PFC appeared after 14 days. A second intravenous injection 5 weeks later induced a 10-fold higher IgM PFC response to LTA which reached a maximum on day 4. An enhanced specific IgG PFC response was also observed. Serum analysis showed further evidence of the anamnestic IgM response to LTA. The results are discussed in terms of the T-dependence of the LTA immunogen.