Primary Plaque-forming Cell Response Research Articles

The effect of methyl linoleate hydroperoxides and radical initiator 2,2'-azobis (2-amidinopropane) dihydrochloride on antibody production by mouse spleen cells.

Methyl linoleate hydroperoxides (MLHPO) and 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH), a widely used free radical initiator, were examined for effects on antibody production by spleen cells using plaque-forming cell response against sheep red blood cells (SRBC). The in vitro primary antibody response was enhanced in the presence of MLHPO at a concentration range of 2-20 microM or AAPH at 0.1 microM, but was suppressed with higher concentrations of these compounds. In the in vitro secondary antibody responses, both MLHPO and AAPH failed to increase plaque-forming cell response above that of the control culture. Following the oral administration of MLHPO (2.29 g/kg) four times to mice, in vivo primary plaque-forming cell response was significantly suppressed. After, a single intraperitoneal injection of AAPH (60 mg/kg) to mice, in vitro primary plaque-forming cell response was also suppressed. These findings suggest that primary antibody response can be affected by lipid hydroperoxides and oxygen radicals in vivo.

Suppression of B-cell mediated immunity in juvenile chinook salmon (Oncorhynchus tshawytscha) after exposure to either a polycyclic aromatic hydrocarbon or to polychlorinated biphenyls.

Juvenile chinook salmon (Oncorhynchus tshawytscha) were injected intraperitoneally with either the polycyclic aromatic hydrocarbon, 7,12-dimethylbenz[a]anthracene (DMBA)1 or with the commercial polychlorinated biphenyl (PCB) mixture, Aroclor 1254, to assess effects on the B-cell mediated immune response. B-cell mediated immunity was assessed by examination of the primary and secondary plaque-forming cell (PFC) responses of anterior kidney and splenic leukocytes to a T-independent antigen, TNP-keyhole limpet hemocyanin (TNP-KLH). Salmon exposed to DMBA at dosages of 20% or 1% of the 96 hr LD50 (12.7 mg and 0.6 mg/kg of salmon, respectively) or to PCBs at a dosage of 20% of the 96 hr LD50 (54.0 mg/kg of salmon) exhibited a suppressed PFC response. The secondary PFC response of anterior kidney and splenic leukocytes to both antigens and the primary splenic PFC response to TNP-LPS were suppressed in salmon exposed to either DMBA or PCBs. However, only the primary PFC response of anterior kidney leukocytes to TNP-LPS was suppressed in salmon exposed to PCBs and no suppression of this response was observed in salmon exposed to DMBA. Neither anterior kidney or splenic leukocytes from salmon exposed to DMBA or PCBs showed an altered primary PFC response to the T-dependent antigen, TNP-KLH. These results suggest that B-cell mediated immunity in salmon is suppressed by known mammalian immunosuppressants and that suppression of the PFC response observed previously in salmon from an urban estuary may be due to contaminant exposure.

In vivo cortisol administration suppresses the in vitro primary immune response of winter flounder lymphocytes

Prolonged (24-day) administration of cortisol to adult winter flounder, Pleuronectes americanus , was found to decrease the in vitro primary immune response of splenic lymphocytes as measured by the passive haemolytic plaque assay. Intraperitoneal implantation of fish with cortisol mixed into a vegetable shortening and cocoa butter vehicle resulted in elevated serum cortisol levels that were within physiological ranges. Existing techniques for piscine lymphocyte culture were modified for use with winter flounder. Longer durations of elevated serum cortisol in the fish produced a more marked suppression of the plaque-forming cell (PFC) response. The suppression was evident as early as 10 days postimplantation when winter flounder cultures were stimulated for 14 days with trinitrophenyl-keyhole limpet haemocyanin (TNP-KLH). Suppression of the PFC response was not apparent until 17 days postimplantation in those cultures stimulated with trinitrophenyl-lipopolysaccharide (TNP-LPS) and was less apparent when the culture period was lengthened from 9 days to 14 days. Our results indicate that the in vitro primary PFC response can be used to evaluate the presence of chronic stress in fish.

Comparative immunosuppression of various glycol ethers orally administered to Fischer 344 rats

Oral dosing of adult male F344 rats with the glycol ether 2-methoxyethanol (ME) or its principal metabolite 2-methoxyacetic acid (MAA) results in the suppression of the primary plaque-forming cell (PFC) response to trinitrophenyl-lipopolysaccharide (TNP-LPS). In the present study, the PFC response to TNP-LPS was used to evaluate the immunotoxic potential of ethylene glycol (EG) as well as the glycol ethers 2-methoxyethyl acetate (MEA), 2-(2-methoxyethoxy) ethanol, bis(2-methoxyethyl) ether, 2-ethoxyethanol and its principal metabolite 2-ethoxyacetic acid, 2-ethoxyethyl acetate, and 2-butoxyethanol relative to ME and MAA. Rats were immunized with TNP-LPS and then exposed 4 and 28 hr later to 50, 100, 200, or 400 mg/kg of glycol ether or EG. Three days following immunization, the PFC response to TNP-LPS was determined. In addition to ME and MAA, only MEA, which was as effective as ME, suppressed the PFC response to TNP-LPS. Concomitant administration of the alcohol dehydrogenase inhibitor 4-methylpyrazole with ME or MEA prevented suppression of the PFC response by these glycol ethers. These results indicate that of the chemicals tested only ME, MEA, and MAA are immunosuppressive, and that oxidative metabolism via alcohol dehydrogenase is necessary for ME- and MEA-suppression of the response to TNP-LPS.

Identification of t-helper cells as the target of stearic acid-inhibition in primary antibody responses in vitro

We have previously shown that albumin-complexed stearic acid (18:0) inhibited in vitro primary anti-TNP plaque-forming cell (PFC) responses to trinitrophenyl keyhole limpet hemocyanin (TNP-KLH), but did not affect primary PFC responses to trinitrophenyl lipopolysaccharide (TNP-LPS). The present studies were done to identify the cellular target of fatty acid inhibition. The addition of 18:0 at the initiation of antibody cultures exerted a dose-dependent inhibitory effect on subsequent PFC responses to TNP-KLH, and removal of the fatty acid after 20 h did not reverse its inhibitory effect. Preincubation of isolated T-cells with TNP-KLH and 18:0 resulted in a similar inhibition of subsequent PFC responses, but a preincubation of isolated B-cells had no effect. The addition o of 18:0 to the culture system in vitro led to a marked reduction in the level of IL-2 detectable in culture supernatants, and PFC responses could be restored by providing exogenous mouse recombinant IL-2. The addition of antigen-primed T-helper cells to antibody cultures partially abrogated the inhibition by 150 μM 18:0, apparently due to their greater production of IL-2. Lastly, following overnight incubation of unfractionated splenic lymphocytes in the presence of TNP-KLH and [1- 14C]-18:0, B-cells were shown to contain nearly 5-fold more radiolabeled oleic acid (18:1) than T-cells. Collectively, these findings implicate T-helper cells as the principle target of 18:0-inhibition of primary antibody responses in vitro, possibly as a result of the inability of T-helper cells to avoid an over accumulation of stearic acid in their membrane phospholipids.

Immunomodulatory effects of footshock in the rat

Intermittent inescapable footshock (IIFS) treatment, administered to 3-month-old male rats, resulted in analgesia as well as discrete immunological and endocrine changes. The splenic lymphocyte proliferative response to concanavalin A (ConA) and phytohemagglutinin (PHA) was decreased by 20% and 41%, respectively. The primary IgM plaque forming cell (PFC) response to sheep red blood cells (SRBC), however, was not altered by IIFS administered either immediately or 24 h after injection of SRBC. IIFS also produced a significant (20-fold) increase in plasma corticosterone (CORT) as compared to non-shocked controls. The shock-induced suppression of splenic lymphocyte mitogenic response to PHA was blocked by 10 mg/kg naltrexone (NTX) administered immediately before IIFS. NTX alone had no effect on this mitogen response. However, NTX significantly attenuated the shock-induced rise in CORT even though NTX alone significantly elevated CORT in the non-shocked controls. These data suggest that IIFS alters cellular immune response but not the primary IgM PFC response (a measure of humoral immune function) and that the immunomodulatory effects may involve both an opioid and a corticosteroid component with respect to alterations in the splenic lymphocyte mitogenic response to PHA.

Mechanisms of specific immunological unresponsiveness to bacterial lipopolysaccharides.

Low-dose priming of mice with Escherichia coli O113 lipopolysaccharide (LPS) results in the development of immunological memory, whereas low-dose priming with E. coli O55 LPS or Serratia marcescens LPS induces significant antigen-specific unresponsiveness. All three preparations of LPS induced proliferation of mouse splenocytes with similar time course and [3H]thymidine uptake. There was no correlation between the small amounts of serum antibody detected by enzyme-linked immunosorbent assay after low-dose priming and the subsequent generation of either memory or unresponsiveness. Further, the passive transfer of small amounts of LPS-specific antibody had no significant effect on the magnitude of the plaque-forming cell (PFC) response elicited after subsequent immunization. Reduction of the PFC response to E. coli O55 LPS occurred after low-dose priming of nu/nu (as well as nu/+) mice; however, unresponsiveness could not be generated in nu/nu mice by low-dose priming with S. marcescens LPS. Thus, although the development of low-dose unresponsiveness to S. marcescens LPS appears to involve T cells, the response of E. coli O55 LPS does not. Enhancement of the primary PFC response to S. marcescens LPS could be transferred with low-dose primed spleen cells depleted of Lyt-2+ T cells; this suggests that the magnitude of the PFC response to this preparation of LPS is negatively influenced by Lyt-2+ T cells and positively influenced by Lyt-2- spleen cells (i.e., L3T4+ T cells). These findings indicate that T cells appear to be involved in regulating the magnitude of the antibody response to some types of bacterial LPS.

Regulation of immune responses by T cell subsets. Role of helper and suppressor T cells in the development and expression of MHC-restricted antibody responses to L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT) by (responder X responder)F1 spleen cells.

The roles of helper and suppressor T cells in the development and expression of antibody responses to GAT were studied in (responder X responder)F1 mice immunized with parental GAT-M phi. Spleen cells from (B10 X B10.D2)F1 mice primed in vivo with B10 or B10.D2 GAT-M phi developed secondary in vitro plaque-forming cell (PFC) responses only when stimulated by GAT-M phi syngeneic with the GAT-M phi used for in vivo priming. By contrast, virgin F1 spleen cells developed comparable primary PFC responses to both parental GAT-M phi Co-culture of T cells from (B10 X B10.D2)F1 mice primed in vivo by B10 GAT-M phi with virgin (B10 X B10.D2)F1 spleen cells demonstrated the presence of suppressor cells that inhibited the primary response of virgin spleen cells stimulated by B10.D2 GAT-M phi. Spleen cells from (B10 X B10.D2)F1 mice primed in vivo with B10.D2 GAT-M phi had suppressor T cells that suppressed primary responses stimulated by B10 GAT-M phi. The suppressor T cell mechanism was composed of at least two regulatory T cell subsets. Suppressor-inducer T cells were Lyt-2-, I-J+ and must be derived from immune spleen cells. Suppressor-effector T cells can be derived from virgin or immune spleens and were Lyt-2+ cells. When the suppressor mechanism was disabled by treatment with 1000 rad gamma irradiation or removal of Lyt-2+ cells, Lyt-2-helper T cells from (B10 X B10.D2)F1 mice primed with B10 GAT-M phi provided radioresistant help to virgin F1 B cells stimulated by B10 but not B10.D2 GAT-M phi. Suppressor inducer Lyt-2-,I-J+ cells from B10 GAT-M phi-primed (B10 X B10.D2)F1 mice were separated from the primed Lyt-2-,I-J-helper T cells. In the presence of Lyt-2+ suppressor effector cells, the Lyt-2-,I-J+ suppressor-inducer suppressed the primary response of virgin spleen or virgin T plus B cells stimulated by both B10 and B10.D2 GAT-M phi. Therefore, suppressor T cells were able to suppress primary but not secondary GAT-specific PFC responses stimulated by either parental GAT-M phi. These results showed that immunization of (responder X responder)F1 mice with parental GAT-M phi results in the development of antigen-specific helper and suppressor T cells. The primed helper T cells were radioresistant and were genetically restricted to interact with GAT in association with the major histocompatibility complex antigens of the M phi used for in vivo priming.(ABSTRACT TRUNCATED AT 400 WORDS)

Genetic restrictions in the development of antibody responses to L-glutamic acid60-L-alanine30-L-tyrosine10 by nude mice implanted with semiallogeneic thymus glands.

Athymic nude mice implanted with F1 thymus glands were used to investigate genetic restrictions regulating T cell-macrophage (M phi) interactions in the development of antibody responses to GAT. Spleen cells from conventional mice developed comparable primary plaque-forming cell (PFC) responses when stimulated by syngeneic and allogeneic GAT-M phi. However, spleen cells from strain A nude mice implanted with (A X B)F1 thymus glands were tolerant of strain B alloantigens and developed GAT-specific PFC responses to strain A GAT-M phi and allogeneic strain C GAT-M phi, but failed to respond to strain B GAT-M phi. The lack of primary GAT-specific PFC responses by spleen cells from (A X B)thy----A nude mice stimulated by strain B GAT-M phi was not due to detectable suppressor mechanisms. However, an allogeneic effect stimulated by H-2- or non-H-2-disparate GAT-pulsed or unpulsed M phi was able to overcome the inability of spleen cells from (A X B)F1 thy----A nude mice to respond to strain B GAT-M phi. Furthermore, the inability to respond to strain B GAT-M phi was overcome by the addition of supernatant fluids from independent cultures of H-2-disparate cells. These results 1) demonstrate that T cells from A nude mice implanted with (A X B)F1 thymus glands did not recognize nominal antigen in the context of B MHC antigens, and 2) suggested that the T cell repertoire was altered in strain A nude mice implanted with (A X B)F1 thymus glands, such that T cells that could recognize GAT in association with strain B MHC antigens were functionally deleted.

Characterization of mixed allogeneic chimeras. Immunocompetence, in vitro reactivity, and genetic specificity of tolerance.

Mixed allogeneically reconstituted mice (B10 + B10.D2----B10) that specifically accept B10.D2 tail skin allografts were examined for in vivo and in vitro immunocompetence, patterns of hematopoietic repopulation, and in vitro reactivity. In vitro, mixed allogeneic chimeras (B10 + B10.D2----B10) manifested specific tolerance in mixed lymphocyte reactions and cell-mediated lympholysis to B10 and B10.D2 splenocytes, with normal responses to third-party (B10.BR) cells. Such chimeras were immunocompetent in B cell and helper T cell responses, as assessed by their primary plaque forming cell responses to in vivo sheep red blood cell immunization. This is in contrast to fully allogeneic chimeras, which responded less well. In addition, survival of the mixed allogeneic chimeras in a conventional animal facility was superior to that of fully allogeneic chimeras, and similar to syngeneically reconstituted (B10----B10) mice. Specific tolerance to skin grafts, degree of allogeneic engraftment, and persistence of chimerism was also assessed in a noncongenic mixed allogeneic combination (B10 + C3H----B10). Such animals manifested specific hyporeactivity to C3H skin allografts, but eventual chronic rejection of the grafts occurred in spite of stable and persistent mixed chimerism. MHC-congenic (B10.BR) skin grafts were accepted indefinitely in the same animals, suggesting that skin-specific non-major histocompatibility complex antigens were responsible for rejection of the C3H skin allografts.

Suppression of primary antibody response by a single exposure to cadmium in mice

Suppression of primary antibody response to sheep red blood cells (SRBC) by a single intraperitoneal (i.p.) injection of cadmium into mice was investigated by the methods of in vitro plaque-forming cell (PFC) assay. BALB/c mice were given 1.8 mg cadmium kg body weight, and 1, 2 or 7 days later, spleen cells from exposed and control mice were cultured with SRBC. PFC responses of all exposed groups were significantly suppressed compared to those of control groups. Addition of control adherent cells to spleen cells from exposed mice failed to recover control level. In the cell-reconstitution experiments, the activity of B-cell function from the exposed group was suppressed more by cadmium than that of T-cell function. These results suggest that the suppression of primary PFC response by cadmium exposure may be caused by the inactivation of B-cells.

Delayed maturation of the antibody response to type 2 thymus-independent antigens in a partially inbred strain of chicken.

The ontogeny of antibody responses to trinitrophenylated (TNP) thymus-independent (TI) antigens was compared in two partially inbred strains of chicken: the SC strain (B2/B2 genotype) and the FP strain (B15/B22 genotype). In the SC chicken, maturation of both the splenic anti-TNP plaque-forming cell (PFC) response and the 19S hemagglutinating antibody response to TI type 2 (TI-2) antigens, TNP-Ficoll and TNP-dextran, were delayed to a significantly later time in ontogeny (20 wk of age) than in the FP chickens (9 wk of age). Four- to 6-wk-old SC chickens were virtually immunologically unresponsive to stimulation with TI-2 antigens. The TI-1 antigen TNP-Brucella abortus was equally immunogenic in both FP and SC chickens of different age groups tested. Kinetic studies of the primary PFC response to TNP-Ficoll in immunologically mature chickens of the SC and FP strains demonstrated a peak PFC response 4 days after antigen injection, followed by a rapid decline in numbers of splenic PFC/spleen on day 6. The results of these studies are discussed in relation to earlier observations that suggested there may be a delay or a defect in the ontogeny of the thymus in the SC chicken.

Effect of 1-thiocarbamoyl-2-imidazolidinone on the generation of plaque forming cell responses.

Although 1-thiocarbamoyl-2-imidazolidinone (TCI) is a highly potent modulator of cellular immunity, its effects on humoral immunity have not been investigated. Given orally to mice prior to immunization with sheep red blood cells (SRBC), low TCI doses (10(-14) to 10(-10) g/kg) suppressed primary plaque forming cell (PFC) responses of spleen cells by 50-75%. TCI effects in vivo were dependent on drug dose, antigen dose and time of drug administration relative to immunization. The kinetics of this response were not appreciably altered by TCI. Higher TCI doses, immunization with higher levels of SRBC than required to produce a maximal response or administration of TCI later than 48 hours after immunization resulted in drug effects ranging from slight suppression to mild enhancement of the primary PFC response. TCI given in vivo enhanced primary PFC responses to the T-independent antigen DNP-Ficoll by greater than 700%+. TCI given before a primary immunization suppressed a secondary PFC response to SRBC elicited 28 days later. However, when TCI was given 24 h prior to a secondary immunization, doses greater than 10(-5) g/kg were necessary to suppress the PFC response. The effect of TCI on in vitro immunized spleen cell cultures was similar to that found for in vivo immunized mice. TCI at concentrations up to 10(-1) g/l did not cause a loss of lymphocyte viability or inhibit plaque production by antibody producing cells. Effects of TCI on PFC responses in vitro were reversible if cells briefly exposed to an optimal concentration of drug were washed extensively prior to immunization.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of parasite-specific immune responses in vitro: evidence for suppression of the antibody response to Trypanosoma cruzi.

Using the Mishell and Dutton culture system, we have developed an assay for eliciting and quantifying parasite-specific immune responses in vitro. The ability of spleen cells from noninfected and Trypanosoma cruzi-infected mice to respond to parasite-associated antigens was assessed by examining the primary plaque-forming cell response to trinitrophenylated T. cruzi (TNP-TC). The response to TNP-TC of both normal, noninfected, unprimed mice and mice infected with T. cruzi is T cell dependent and appeared to involve recognition of parasite antigens by T. cruzi-specific T cells. In most experiments, spleen cells from infected mice respond to TNP-TC at levels equal to, or below, that of spleen cells from normal mice. This near "normal" response is in apparent contrast to the suppressed response of spleen cells from infected mice to another antigen (sheep red blood cells) or TNP on a different carrier (TNP-chicken erythrocytes). Demonstration that the response of spleen cells from infected mice to TNP-TC can be potentiated by addition of interleukin 2-containing supernatants or by depletion of plastic and Sephadex G-10-adherent cells suggests that the mechanisms which control the response of infected mice to nonparasite antigens may also limit parasite-specific immune responses.

Physiology of IgD. III. Effect of treatment with anti-IgD from birth on the magnitude and isotype distribution of the immune response in the spleen.

Continued treatment with monoclonal anti-IgD (Ig-5a) from birth in BALB/c mice causes a markedly increased responsiveness to i.v. injected dinitrophenylated ovalbumin (DNP-OVA) with Bordetella pertussis at the age of 8 weeks. The 19S plaque-forming cell (PFC)/spleen response is particularly enhanced, 6-8-fold, but all the other isotypes also show increases of 2-6-fold, including IgA and IgE. Both primary and secondary PFC responses and serum antibody titers are enhanced. After transfer of spleen cells from anti-Ig-treated mice to irradiated recipients the IgM/IgG ratio becomes similar to that of controls. In contrast, the response of anti-IgD-treated mice to i.p. immunization with either 0.2 or 100 micrograms DNP-OVA plus alum is reduced by approximately 80% for each Ig isotype except IgM and remains low upon transfer of spleen cells to recipients. It is concluded that the paucity of B cells in peripheral lymph nodes of the anti-IgD-treated mice causes the low responsiveness to i.p. immunization, but that the IgD- B cells in the spleen are quite able to respond and are, in fact, more responsive than IgD+ B cells. This increased responsiveness, together with the higher IgM/IgG ratios for all Ig isotypes and an otherwise similar order of isotype distribution (gamma 1 greater than gamma 2b greater than gamma 2a = epsilon greater than or equal to alpha) as in controls, suggests that a hyperresponsive, but less mature IgD- B cell population is selectively produced in the spleens of mice treated with anti-IgD from birth.

Idiotype profile of an immune response. II. Reversal of the relative dominance of major and minor cross-reactive idiotypes in arsonate-specific T-independent responses.

Two different cross-reactive idiotype (CRI) groups are distinguishable in the Ab response of A/J mice to the p-azobenzenearsonate (ABA) hapten: CRIA and CRIm. These two groups showed distinct patterns of relative dominance in the ensuing response depending on whether the inducing Ag was a T cell-dependent (TD) form of ABA, such as ABA-KLH or ABA-CGG, or a T-independent type 1 (TI-1) form, such as ABA-Brucella abortus or ABA-lipopolysaccharide (LPS), and on whether the response was elicited in vivo or in vitro. The CRI+ component of primary in vivo plaque-forming cell (PFC) responses to TD ABA Ags was largely (greater than 90%) CRIA+ as was, to a slightly lesser extent (greater than 75%) the CRI+ portion of secondary or hyperimmune serum Ab or PFC responses to the same Ags. In contrast, in vivo primary and hyperimmune PFC responses to ABA-Bru or ABA-LPS showed a significantly lower CRIA/CRI ratio, averaging 0.5-0.6, with some individual mice giving figures as low as 0.2, indicating predominance of CRIm over CRIA. Serological analysis of hyperimmune anti-ABA Abs from a group of 5 A/J mice immunized with ABA-Bru gave a figure of less than 0.5 for the CRIA/CRI ratio. The most striking disparity from the TD pattern was seen in primary in vitro PFC responses to the TI ABA Ags; here ratios of less than 0.2 were generally seen. Since T cell removal did not alter the Id pattern in the TI responses, CRIA-specific Ts cells do not account for the weak expression of CRIA in such responses. We propose a model that explains these results on the basis of differential expression of IdX dominance by two distinct B cell subpopulations--equatable to the Lyb-5+ and Lyb-5- B cell subsets--along with differential relative activation of these subsets in different types of responses. Examination of anti-ABA PFC responses of F1 progeny of CBA/N and A/J mice to ABA-Bru lends support to this hypothesis since CRIA expression was significantly lower in mice with the xid defect.

Immunoregulation in MRL/Mp-lpr/lpr mice: Evidence for decreased helper-T-cell and increased suppressor-T-cell function with age

In vivo and in vitro plaque-forming cell (PFC) responsiveness to sheep erythrocytes (SRBC) was used to assess immunoregulatory function in the autoimmune MRL mouse strain. MRL/Mp-lpr/lpr (MRL/l) mice had good primary and secondary IgM and IgG responses in vivo compared to MRL/Mp-+/+ (MRL/n) mice when young, but with age the MRL/l responses declined markedly. In vitro primary SRBC-specific PFC responses in MRL/l mice declined at the same time as in vivo responses, indicating that the in vivo autoimmune environment could not account for cellular dysfunction. When varied mixtures of T and B cells from MRL/l and MRL/n mice were cultured, abnormalities in MRL/l T-cell function became apparent. T-helper-cell (T H) function declined rapidly with age, beginning by 2 to 2 1 2 months of age. T cells from MRL/l mice 2 months of age and older also had increased suppressor activity when cultured with B cells and MRL/n T cells. The degree of suppressor activity increased with age. The correlation of these findings with results of previous studies by others and with autoimmune disease is discussed.

In vitro evaluation of cadmium-induced augmentation of the antibody response

Augmentation of in vitro primary plaque-forming cell (PFC) response by cadmium exposure was investigated. Spleen cells from 2- to 3-months-old BALB c mice were incubated with various concentrations of cadmium chloride in the presence of sheep red blood cells (SRBC) as an antigen. PFC responses were enhanced by 4 and 8 μ m cadmium, but suppression of PFC responses was observed at concentrations of 20 and 40 μ m cadmium. In the reconstitution of adherent and nonadherent cells to culture dishes from spleen cells which were incubated for 24 hr with 8 μ m cadmium or saline (control), it was found that nonadherent cells were significantly enhanced by cadmium. Moreover, in the reconstitution between T and B cells from control and exposed groups, B cells from exposed groups were more enhanced by cadmium than T cells. These results suggested that augmentation of primary PFC response by cadmium exposure was mainly caused by the enhancement of B cells.

Enhancement of immune response by inflammatory response, with special reference to a role of PMN- derived soluble factor

Inflammatory responses, which were induced in the peritoneal cavity of mice by a variety of stimuli, produced an enhanced immune response to sheep erythrocytes when the antigen was introduced at an early stage of the inflammatory responses. The enhancement could be reproduced when early peritoneal exudate cells, consisting mostly of neutrophils, were adaptively transferred at the same time as antigen. The neutrophils were shown to produce a lymphocyte-activating soluble factorin vivaandin vitro. The PMN-derived factor produced the enhancement of several lymphocyte functions, including T-cell proliferative response, primary plaque forming cell response and allo-reactive killer T cell response.The PMN factorper sewas non-mitogenic and exhibited maximum potentiation of T lymphocyte response when added within 3 hr of antigen or mitogen stimulation. Mitogen-stimulated, but not nonstimulated thymocytes absorbed PMN factor activity.125I-labelled factor binding to stimulated thymocytes was proved. Thus, it is suggested that an acceptor site for PMN factor may be generated on the thymocyte surface only after mitogen stimulation.The PMN factor was composed of two isoelectrophoretically distinct factors, a cationic (pI 9.8) and a neutral (pI 5.4) PMN factor. The two purified, 125I-labelled PMN factors were homogeneous on SDS-PAGE. Their molecular weights were calculated to be 19, 000 for cationic-and for 21, 000 neutral PMN factor by Svedberg equation.

Role of Ia. W39 in the interaction of antigen-presenting cells with T and B lymphocytes.

Ia. W39 is a B cell differentiation antigen whose membrane expression is controlled by the xid gene. In this report we show that, analogous to its B cell expression, Ia. W39 is also present on a subset of Ia+ macrophages, indicating heterogeneity within that cell population. The Ir gene(s) for the antigenic determinants on the A chain loop of beef insulin maps to the I-Ab subregion of the H-2 complex and, as we have previously reported, is associated with the private specificity Ia. W39. Depletion of Ia. W39+ macrophages eliminates their capacity to present beef insulin to immune T cells, whereas the presentation of the multideterminant antigen trinitrophenylated ovalbumin is reduced less than 50%. Furthermore, we found that H-2b mice lacking Ia. W39+ cells are unable to make a secondary in vivo IgG plaque-forming cell (PFC) response to beef insulin, while the primary IgG PFC response is not dependent on Ia. W39. No shift in the kinetics of the response, nor development of suppressor T cells could be detected in Ia. W39- mice, which would explain their apparent nonresponsiveness to beef insulin after boosting with this antigen. These results, therefore, may reflect a difference in the Ir gene control acting at the primary vs. secondary response level.