Regulation of the antibody response to type 3 pneumococcal polysaccharide. I. Nature of regulatory cells

Marginal zone B cells in lymphocyte activation and regulation

Marginal zone (MZ) B cells, together with other strategically located innate cells, constitute the first line of defense against blood-borne microorganisms, viruses and toxins in the spleen. Their fast and efficient protective antibody responses are well characterized; however, much less is known of their interactions with other cell types during immune responses. Recent work has demonstrated that MZ B cells can directly activate T cells; and MZ B cells also interact with other antigen presenting cells, transporting and concentrating antigen during the course of T-dependent and T-independent immune responses.

The mechanism underlying T cell help for induction of an antigen-specific in vivo humoral immune response to intact Streptococcus pneumoniae is dependent on the type of antigen

Little is known concerning the role of T cells in regulating an anti-polysaccharide Ig response to an intact pathogen. We previously reported that the in vivo Ig responses to Streptococcus pneumoniae (strain R36A), specific for pneumococcal surface protein A (PspA) and for the phosphorylcholine (PC) determinant of C-polysaccharide, were both dependent on TCR-alphabeta(+) T cells and B7-dependent costimulation, although only PspA-specific memory was generated. In this report, we show that the T cell help underlying these two Ag-specific Ig responses is distinct. Using H-Y-specific T cell transgenic mice made "nonleaky" by crossing with mice genetically deficient for TCR-alpha, we demonstrate that the T cell help for the anti-PC, in contrast to the anti-PspA, response is TCR-nonspecific and occurs normally in the absence of germinal center formation, although it is still dependent on B7-dependent costimulation. Consistent with these data, we demonstrate, using cathepsin S(-/-) mice, that although the anti-PC response is largely dependent on CD4(+) T cells, there is a reduced (or lack of) dependence, relative to the anti-PspA response, on the generation of new peptide-MHC class II complexes. In this regard, the T cell help for an optimal anti-PC response is delivered more rapidly than that required for an optimal anti-PspA response. Collectively, these data demonstrate a novel accelerated TCR-nonspecific B7-dependent form of T cell help for augmenting a polysaccharide-specific Ig response to an intact bacterium without the generation of memory.

Essential role for CD40 ligand interactions in T lymphocyte-mediated modulation of the murine immune response to pneumococcal capsular polysaccharides

Protection against infection with pneumococci is provided by anti-capsular polysaccharide (caps-PS) Abs. We investigated whether CD40 ligand (CD40L) plays a role in T lymphocyte-mediated regulation of the immune response to caps-PS, which are considered thymus-independent Ags. Administration of MR1, an antagonist mAb against murine CD40L, in BALB/c mice immunized with Pneumovax resulted in an inhibition of the IgM and IgG Ab response for various caps-PS serotypes. Evidence for the involvement of CD4(+) T lymphocytes in the Ab response to caps-PS was obtained in SCID/SCID mice that, when reconstituted with B lymphocytes and CD4(+) T lymphocytes, mounted a higher specific IgM response compared with SCID/SCID mice reconstituted with only B lymphocytes. This helper effect of CD4(+) T lymphocytes was abrogated by MR1. Blocking CD40L in vitro decreased the IgM response to caps-PS and abolished the helper effect of CD4(+) T lymphocytes. CD8(+) T lymphocyte-depleted murine spleen cells mounted a higher in vivo immune response than total murine spleen cells, which provided evidence for a suppressive role of CD8(+) T lymphocytes on the anti-caps-PS immune response. CD4(+) T lymphocyte-depleted murine spleen cells, leaving a B and CD8(+) T lymphocyte fraction, elicited only a weak in vivo and in vitro Ab response, which was enhanced after MR1 administration. In summary, our data provide evidence that T lymphocytes contribute to the regulation of the anti-caps-PS immune response in a CD40L-dependent manner.

Okadaic acid-like toxin in systemic lupus erythematosus patients: hypothesis for toxin-induced pathology, immune dysregulation, and transactivation of herpesviruses

Preliminary evidence suggests there is a toxin in the sera of systemic lupus erythematosus patients which reacts with a commercial enzyme-linked immunosorbent assay kit for the detection of the marine toxin, okadaic acid. Data is presented which supports the hypothesis that an okadaic acid-like toxin may be the principle agent of lymphocyte dysregulation in systemic lupus erythematosus and other immune-dysregulated states. The okadaic acid-like toxin can produce the specific abnormalities in T-lymphocyte phenotype and function typical of systemic lupus erythematosus, principally through its ability to inhibit serine/threonine phosphatases necessary for secondary signalling processes and through its ability to inhibit calcium which is crucial to protein kinase C-mediated signalling of T-lymphocytes. The disruption probably occurs through the protein tyrosine kinase p56lck pathway crucial for IL-2. Additionally, the toxin's ability to disrupt voltage-sensitive ion channels in cell membranes may be responsible for the multi-organ pathology observed in systemic lupus erythematosus patients, particularly neurological, cardiac and nephritic. Data from a different study conducted by the author suggests that latent and persistent viruses are reactivated in active lupus. This activation could be the result of the toxin's ability to act as an immune modulator, or its ability to act as a transactivating factor.

Deficient antipneumococcal polysaccharide responses in HIV-seropositive patients

In a prospective study, serological responses and opsonic activity towards Streptococcus pneumoniae were measured in 60 HIV-infected patients and 25 controls after the administration of the 23-valent pneumococcal vaccine (PneumovaxR). Serum samples were collected before vaccination and at weeks 1, 2, 4, and 12 after vaccination and were tested for the presence of antibodies against a mixture of capsular polysaccharide antigens (pool) and against type 3 and type 4 antigens (PS3 and PS4), using an ELISA. A serological response was defined as a two-fold or greater increase in serum titer after vaccination. Opsonophagocytosis was measured in patients with a definite response against PS3. Generally, prevaccination antipneumococcal antibody titers were clearly higher in HIV-infected patients than in healthy controls. After vaccination, antipool antibody responses were found in 76% of vaccinated patients; 24% of the patients were non-responders. In patients with more than 0.300 x 10(9) CD4 + cells per liter the percentage of responders was 94%; in patients with fewer than 0.300 x 10(9) CD4 + cells per liter this percentage was 68% (P < 0.05). The antipool response in control subjects was 92%. A serological response to PS3 and PS4 was found in 29% and 49% of the patients, respectively, and was correlated with CD4 + cell count. In controls, these percentages were 48% and 92%, respectively. In 30% of responding patients, antibody titers dropped already to prevaccination levels by week 12 after vaccination. Opsonophagocytosis was not significantly improved by vaccination, probably because of a relatively high preexisting opsonic activity. Although prevaccination conditions may have had an important influence on the study outcome, the results are not in favor of a significant beneficial effect of vaccination with PneumovaxR on antibody formation in HIV-infected patients. This raises further questions as to the relevance of pneumococcal vaccination in this population.

T-cell-dependent and T-cell-independent mechanisms of tolerance to glucuronoxylomannan of Cryptococcus neoformans serotype A

Glucuronoxylomannan (GXM), a type 2 T-independent antigen, is the major component of the capsular polysaccharide (CnCAP) of Cryptococcus neoformans. Previous studies have described the tolerogenic effects of high doses of CnCAP on the specific humoral response. In this investigation, evidence for both high-dose and low-dose tolerance to GXM is presented. BALB/cBy female mice, primed with either 5 ng or 50 micrograms of GXM, then coimmunized 3 days later with immunogenic doses of both GXM and type 3 pneumococcal polysaccharide (SSS-III), showed an antigen-specific inhibition in their splenic plaque-forming cell (PFC) responses to GXM compared with control groups primed with normal saline. SSS-III PFCs remained unchanged between GXM-primed and normal saline-primed groups. Low-dose tolerance appeared to be T dependent, whereas high-dose tolerance appeared to be T independent. Low-dose tolerance to GXM could not be induced in athymic BALB/c nu/nu mice, whereas high-dose tolerance in the same mice could be induced. Furthermore, low-dose tolerance was adoptively transferred with B-cell-depleted splenocytes to naive BALB/c mice, while high-dose tolerance was not. Complement-mediated depletion of CD4+ but not CD8+ splenocytes from low-dose-primed mice abrogated the transfer of low-dose tolerance. These findings indicate T-dependent and T-independent mechanisms of antigen-specific B-cell tolerance to GXM in BALB/c mice at low and high antigen doses, respectively.

The glucuronoxylomannan of Cryptococcus neoformans serotype A is a type 2 T-cell-independent antigen

The humoral immune response of inbred mice to immunization with the glucuronoxylomannan (GXM) of Cryptococcus neoformans was investigated both serologically and in plaque-forming cells (PFCs). The T-helper-cell-independent quality of the GXM was demonstrated by using BALB/c nu/nu mice. Primary and secondary dose responses to three antigenic forms of GXM, (i) the native antigen, (ii) a GXM-bovine serum albumin protein conjugate, and (iii) a cryptococcal whole-cell vaccine, revealed a lack of isotype class switching and anamnestic responses. Both the levels of complement-fixing anti-GXM antibody in serum and the PFC responses in the athymic mice showed no significant differences from those in the wild-type controls. However, T cells are involved in the suppression of the primary response to GXM. When BALB/cBy mice were given rabbit anti-mouse thymocyte serum along with 0.5 microgram of GXM, both antibody levels in serum and PFC responses were significantly increased over those of control mice that received GXM and normal rabbit serum. In addition, T cells were also shown to enhance the primary immune response to GXM. BALB/cBy mice were given GXM and anti-mouse thymocyte serum on day 1. On day 2, the experimental group was given anti-mouse thymocyte serum and the control group was given saline. On day 5, comparison of the PFC responses and anti-GXM antibody titers of the two groups revealed a significant increase in the immune response of the control over the experimental group. The type 2 T-cell-independent quality of GXM was also demonstrated in CBA/cHN xid mice. These mice lack the Lyb+ subset of B cells and are unable to respond to type 2 T-independent antigens but respond normally to type 1 T-independent antigens. Type III pneumococcal polysaccharide, a type 2 T-independent antigen, was used as a negative control, and trinitrophenyl-lipopolysaccharide, a type 1 T-independent antigen, was used as a positive control. The CBA/cHN xid mice failed to respond to either type III pneumococcal polysaccharide or GXM but did not respond to immunization with trinitrophenyl-lipopolysaccharide. BALB/cBy mice responded normally to all three antigens.

Adenosine-deaminase-associated immunodeficiency. I. Differential sensitivities of lymphocyte subpopulations exposed to 2-deoxycoformycin in vivo

In order to obtain a better understanding of the degree of immune dysfunctions caused by the absence of adenosine deaminase, we gave a single i.p. injection of 2'-deoxycoformycin (2-dcf), a potent inhibitor of the enzyme ADA at various doses into adult Syrian hamsters. These animals were examined for their ability to mount primary in vivo antibody responses to helper T cell dependent (Th-d) and helper T cell independent (Th-ind) antigens. Hamsters treated with 0.5 mg/kg of 2-dcf mounted enhanced splenic plaque-forming cell (PFC) responses to sheep erythrocytes, a Th-d antigen, and to pneumococcal polysaccharide type III (SIII), a Th-ind antigen. Treatment of animals with 1.0 mg/kg of 2-dcf resulted in a significantly depressed (P less than 0.001) PFC response to Th-d antigen, but a further enhanced response to Th-ind antigen. One mechanism which may be responsible for such a dichotomous response to these two types of antigens was selective dysfunction of T cell subpopulations. At higher doses (1.5-4.0 mg/kg), PFC responses to both types of antigens were significantly suppressed. Immunoenhancement at low doses of 2-def was attributed to an increased susceptibility of T suppressor cells to 2-dcf. This hypothesis was confirmed by priming the 2-dcf-treated animals with low-dose Th-ind antigens. These animals failed to induce low-dose tolerance by stimulation of antigen-specific suppressor T cell subsets. At low doses, B cells and T helper cell functions were found to be intact, as further confirmed by priming the animals with the carrier keyhole limpet haemocyanin (KLH) and challenging with trinitrophenyl-KLH. This dose-dependent selective susceptibility of various T cell subpopulations and B cells may explain the heterogeneity of clinical, biochemical and immunological parameters observed in children with ADA deficiency severe combined immunodeficiency.

The amplifier role of T cells in the human in vitro B cell response to type 4 pneumococcal polysaccharide

The human B cell response to T cell independent type 2 antigens is regulated by thymus-derived lymphocytes. We analyzed the role of T cells in the in vitro antibody response to type 4 pneumococcal polysaccharide (PS4). We here show that the amplifying effect of T cells, which has previously been shown to be radioresistant and confined to T cell preparations enriched for CD4+ cells, is MHC non-restricted as demonstrated in cultures carried out in the presence of allogeneic T cells. Also, T cell clones derived from non-related donors are able to enhance the B cell response to PS4. All TCR alpha beta +, CD 4+ T cell clones, but none of the TCR alpha beta +, CD 8+ T cell clones tested, enhanced the B cell response to PS4. Furthermore, 3 out of 6 TCR gamma delta+ T cell clones were capable of enhancing the anti-PS4 B cell response. Experiments using recombinant lymphokines and glutaraldehyde-fixed T cells indicated that both lymphokines and T-B cell interactions are required for an optimal antibody response to PS4.

In Vitro Activation of Human T Lymphocytes by Haemophilus influenzae Type b Capsular Polysaccharides

Polyribosilribitolphosphate (PRP), the capsular polysaccharide from Haemophilus influenzae type b, is a T-cell-independent type 2 antigen. In vitro culture of adult peripheral blood T cells with 15 micrograms/ml PRP leads to induction of interleukin-2 receptor (IL-2R) expression on up to 10% of T cells. These cells are CD4+ and carry the alpha beta T-cell receptor. PRP, at concentrations above 1-5 micrograms/ml, can also induce in vitro proliferation of both adult and neonatal T cells. We conclude that PRP acts as a human T-cell mitogen. The in vitro proliferative response as well as IL-2R expression was studied in T cells derived from adults after vaccination with native PRP, with PRP conjugated to a carrier protein, or with diphtheria toxoid. Vaccination with conjugated PRP decreased the doses of PRP required for in vitro induction of IL-2R expression and T-cell proliferation. This indicates that vaccination with PRP conjugated to a carrier protein improves the in vitro T-cell response to PRP activation.

Bacterial Polysaccharides, Endotoxins, and Immunomodulation

These studies show that at least some--though certainly not all--of the adjuvant effects of LPS and its derivatives can be attributed to its ability to eliminate the inhibitory effects of Ts which are activated during the course of a normal immune response. The ability of nontoxic MPL to act in this fashion suggests that it can be used as a safe and acceptable alternative to Freund's complete adjuvant to increase the immunogenicity of poorly immunogenic antigens. More important, the ability of MPL to eliminate the expression of Ts activity, without adversely influencing other T cell functions (e.g., Th, Ta, and Tc activity) makes its use as an adjuvant even more promising since it can then permit those T cell functions to be expressed in a much more efficient manner. Obviously, this would have great significance for the development of tumor immunity.

Antigen specific suppressor T cells respond to cytokines released by T cells

These studies were conducted to examine the cytokine requirement for clonal expansion of regulatory T cells. It was observed that the in vivo administration of recombinant IL2 (rIL2), rIL5 or interferon (IFN) gamma at the time of immunization with pneumococcal polysaccharide Type III (SSS-III) resulted in substantial suppression of the antibody response in each case. Using our well established cell transfer system we found that such suppression of the antibody response could be transferred using 10-100-fold fewer primed spleen cells providing these cells were treated in vitro with rIL2 before cell transfer; spleen cells from unimmunized mice or from mice primed with an unrelated antigen and then treated with rIL2 did not cause suppression of the antibody response to SSS-III, thereby eliminating the possibility of non-specific carry-over effects induced by rIL2. We also found that the in vivo administration of anti-IL2 receptor antibody inhibited the generation of Ts cells in vivo. Spleen cells from SSS-III primed animals treated with rIL4, rIL5 and IFN gamma--but not rIL6--likewise are able to transfer suppression of the antibody response with fewer cells than that required using primed cells not treated with cytokines. Thus, these studies indicate that Ts cell activity is greatly influenced by cytokines. The studies also suggest that these cytokines may be required during the activation and/or clonal expansion of Ts cells.

The human in vitro anti-type 4 pneumococcal polysaccharide antibody response is regulated by suppressor T cells

In order to study the regulation of the human B-cell response to T-cell independent type 2 (TI-2) antigens, we analysed the role of T cells in the in vitro antibody response to type 4 pneumococcal polysaccharide (PS4). We found that T cells can positively regulate the in vitro antibody response to PS4 when they are added into an in vitro B-cell culture system. In addition we demonstrated that T cells exert a negatively regulating activity. We found that T cells, when cultured for 24 h in the presence of high concentrations of PS4, can suppress the anti-PS4 antibody response. This down-regulation of the anti-PS4 B-cell response is shown to be antigen specific and MHC-restricted. Furthermore, PS4-specific T-cell mediated suppression appears to be radioresistant and confined to the T-cell preparations enriched for CD8+ cells. The results show that analogous to results obtained in mice, human T cells are able to exert a regulatory control of the antibody response to TI-2 antigens.

Antigen-specific suppressor T cells respond to recombinant interleukin-2 and other lymphokines

Previous studies have shown that transfer of whole spleen cell populations obtained from primed donors or transfer of purified T cells enriched for suppressor activity (Ts) to recipient mice decreased the antibody response to pneumococcal polysaccharide type III (SSS-III) when the animals were simultaneously immunized with SSS-III. In the present studies, such suppression of the antibody response was transferred with 10- to 100-fold fewer primed spleen cells when the cells were treated in vitro with recombinant interleukin-2 (rIL-2) before transfer; spleen cells from naive mice or mice primed with an unrelated antigen (dextran) and then treated with rIL-2 did not cause suppression of the antibody response to SSS-III, thereby eliminating the possibility of nonspecific carryover effects induced by rIL-2. In vivo administration of rIL-2 at the time of immunization with an optimally immunogenic dose of SSS-III resulted in significant (P less than 0.05) suppression of the antibody response relative to that of control animals, suggesting that IL-2 augments the clonal expansion of Ts cells in vivo. Further, the ability of passively administered anti-IL-2 receptor antibody to inhibit generation of Ts cells in vivo is consistent with such a view. Spleen cells from primed animals treated with rIL-4, rIL-5, or gamma interferon--but not those from primed animals treated with rIL-6--likewise were able to transfer suppression of the antibody response with fewer cells than those required when primed cells not treated with lymphokines were used. Thus, these studies indicate that Ts cell activity is greatly influenced by lymphokines produced by helper T cells. The studies also suggest that these lymphokines are required during activation and/or clonal expansion of Ts cells.

Inactivation of suppressor T cell activity by the nontoxic lipopolysaccharide of Rhodopseudomonas sphaeroides

Antibody responses of mice immunized with type III pneumococcal polysaccharide were examined with and without treatment with nontoxic lipopolysaccharide from Rhodopseudomonas sphaeroides (Rs-LPS). The results obtained were similar to those described previously for mice treated with monophosphoryl lipid A (MPL) except that lower amounts of Rs-LPS were needed. Both were without effect when given at the time of immunization with type III pneumococcal polysaccharide but elicited significant enhancement when given 2 to 3 days later. Such enhancement was T cell dependent and not due to polyclonal activation of immunoglobulin M synthesis by B cells. Treatment with either Rs-LPS or MPL abolished the expression but not induction of low-dose paralysis, a form of immunological unresponsiveness known to be mediated by suppressor T cells (Ts). The in vitro treatment of cell suspensions containing Ts with extremely small amounts of Rs-LPS or MPI completely eliminated the capacity of such cells to transfer suppression to other mice. These findings indicate that the immunomodulatory effects of both MPL and Rs-LPS are mainly the result of eliminating the inhibitors effects of Ts; this permits the positive effects of amplifier T cells to be more fully expressed, thereby resulting in an increased antibody response. The significance of these and other findings to the use of Rs-LPS as a pharmacotherapeutic agent for gram-negative bacterial sepsis is discussed.

Type 6 and 19 pneumococcal polysaccharides coupled to erythrocytes elicit pneumococcal cell wall-specific primary IgM responses and capsular polysaccharide-specific secondary IgG responses

Previous results have shown that the primary murine antibody responses to vaccine preparations of type 6 (S6; Danish type 6A) or type 19 (S19; Danish type 19F) pneumococcal capsular polysaccharides consist entirely of IgM antipneumococcal cell wall carbohydrate (PnC)-specific antibodies. No capsular polysaccharide-specific IgM antibodies were detectable by plaque-forming cell or enzyme-linked immunosorbent assay techniques. In this report, antibodies specific for S6 and S19 capsular polysaccharides were induced in secondary responses to chicken erythrocyte (CRBC) conjugates of S6 and S19. Essentially all detectable IgG produced in the secondary response was capsular polysaccharide specific and included all subclasses of IgG. In contrast, all detectable IgM produced in the primary response to S6-CRBC and S19-CRBC, and the IgM produced in the secondary response to S6-CRBC was not capsular polysaccharide specific since it reacted with PnC. Thus, there is a major change in the specificity of the primary IgM response compared to the secondary IgG response of mice immunized with S6-CRBC or S19-CRBC. Injection of PnC or any PnC-containing polysaccharide prior to immunization with S6-CRBC or S19-CRBC resulted in suppression of the primary IgM response. In contrast, only the capsular polysaccharide used in the immunizing polysaccharide-erythrocyte conjugate suppressed induction of the capsular polysaccharide-specific secondary IgG response. These results suggest that S6 and S19 capsular polysaccharide-specific IgG-producing memory B cells derive from capsular polysaccharide-specific precursors which do not produce detectable antibody after primary immunization.

Functional analysis of lymphocytes subpopulations in experimental cocaine abuse. I. Dose-dependent activation of lymphocyte subsets

The potential role of substance abuse, especially cocaine and alcohol as co-factor in HIV infection and in the development and expression of AIDS has been suggested, but the possible biological role of substance abuse in the development of AIDS is not known. In order to better understand immune system function in chronic cocaine abuse, we have assessed primary B cell responses to helper T-cell independent (TI) and dependent (TD) antigens in inbred Fisher male rats injected with 1.25-5 mg cocaine/kg body weight for 10 days. The ability of cocaine-exposed animals to mount primary in vivo splenic plaque-forming cell (PFC) and serum antibody responses to the TI antigen, pneumococcal polysaccharide type III (SIII), was elevated several-fold when compared with controls. The degree of elevation of humoral antibody responses seemed to be directly related to the dose of cocaine. Primary in vivo B cell responses to the TD antigen, sheep red blood cells (SRBC), was elevated at lower concentrations of cocaine (1.25-2.5 mg/kg) and was found to be significantly suppressed after chronic exposure to the higher concentration (5.0 mg/kg). The elevated primary splenic immunostimulation to TI (SIII) may be attributed to a combination of loss of T suppressor cell control and direct B cell stimulation. Elevated immune responses to SRBC at lower concentrations were attributed to stimulation of T helper cells as well as loss of T suppressor cells. Immunosuppression to SRBC observed in response to 5.0 mg/kg of cocaine was most probably due to loss of T helper cell subset functions. These findings were further tested by in vitro methods, where splenic lymphocytes from cocaine-exposed animals were examined for their ability to respond to concanavalin A (Con A) in terms of the induction of antigen non-specific suppressor T cells. The addition of Con A-stimulated splenic lymphocytes from cocaine-treated animals did not inhibit the primary antibody responses of SRBC as compared with saline-treated controls, indicating that suppressor T cells malfunction after cocaine exposure. Lymphocyte subpopulation analysis using fluorescein-labelled monoclonal antibodies showed a significant increase in the B cell populations at doses of 1.25-5 mg/kg. A reciprocal change in T cell populations also took place. No significant numerical change in macrophage (NSE+) and T cell subset, T helper and T suppressor was noticed, suggesting that cocaine probably directly effects mature T cell subset functions but does not affect their differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)

Interleukin 2 receptor expression by human blood lymphocytes after vaccination with pneumococcal polysaccharides

Proliferative responses of unseparated peripheral blood mononuclear cells (PBMC) and blood T cells to recombinant interleukin 2 (rIL-2) were significantly increased 7-21 days after the vaccination with pneumococcal polysaccharides (PPS). In contrast, non-T cells expressed increased responsiveness to rIL-2 only on post-vaccination day 7. Analysis of the proliferative response to rIL-2 among lymphocyte subsets (CD4+Leu8+, CD4+Leu8-, CD8+Leu8+, CD8+Leu8-, CD20+) in cultures of unseparated PBMC revealed that the CD8+Leu8- T cells expressed increased responsiveness 7-14 days after vaccination, whereas neither CD4+ (Leu8+ and Leu8-) nor CD8+Leu8+ T cells showed significantly increased responsiveness after vaccination. The CD20+ B cells, like non-T cells, expressed increased responsiveness to rIL-27 days after the vaccination only. Expression of the 55 kD low-affinity interleukin 2 receptor (IL-2R, CD 25) on freshly isolated PBMC, as judged by direct fluorescence staining with a MoAb anti-55 kD chain, was low (less than 3%) and an increased expression of this receptor was not detected following vaccination. In contrast, binding of 125I-labelled IL-2 to freshly isolated PBMC increased following vaccination (day 7). Scatchard plot analysis revealed a modest increase in the expression of high-affinity IL-2R (Kd = 1-2 pM), whereas the increase in expression of the 75-kD, intermediate-affinity IL-2R (Kd = 300 pM) was more pronounced (from 195 to 295 (means) receptors per PBMC). It is concluded that, following vaccination with PPS increased IL-2R expression is induced on blood lymphocytes. These investigations suggest a role for T cells in the human immune response against PPS.

Anti-thymocyte serum delays clearance of poliovirus from the mouse central nervous system

Antibody is of primary importance for protection from poliovirus-induced paralysis (poliomyelitis) and from other enterovirus infections. However, the components of the immune response involved in the clearance of an established enterovirus infection of the central nervous system (CNS) are not known. To assess the effect of thymus-dependent immune functions on a CNS poliovirus infection, adult BALB/c mice inoculated intracerebrally with the W-2 strain of human poliovirus type 2 (PV2) were treated with anti-thymocyte serum (ATS) and analyzed for clinical disease, virus persistence, antibody responses, and T-cell proliferation (Tprlf). Half (22 of 44) of the ATS-treated mice showed paralysis and death as compared to 27% (17 of 62) of control mice treated with normal rabbit serum. Virus persisted in the brain for 45 days after infection in 43% (13 of 30) of ATS-treated mice as compared to 3% (1 of 30) of controls. Tprlf to PV as well as Tprlf and antibody responses to control antigens were markedly reduced in ATS-treated mice. However, antibody responses to PV in ATS-treated mice were not suppressed, suggesting that PV may be a T-cell-independent antigen. These findings indicate that ATS-suppressible functions contribute to the clearance of PV from the mouse CNS, apparently via a sensitized T-cell mechanism.

Inactivation of suppressor T-cell activity by nontoxic monophosphoryl lipid A

Treatment with nontoxic monophosphoryl lipid A (MPL), which was derived from a polysaccharide-deficient, heptoseless Re mutant of Salmonella typhimurium, was found to inactivate suppressor T-cell activity, as evidenced by a decrease in the degree of low-dose immunological paralysis expressed and an increase in the magnitude of the antibody response to type III pneumococcal polysaccharide. The effects produced, which could not be attributed to the polyclonal activation of immune B cells by MPL, were dependent upon the dose of MPL used, as well as the time when MPL was given relative to low-dose priming or immunization with type III pneumococcal polysaccharide. Neither amplifier nor helper T-cell activity was decreased by treatment with the same, or larger, doses of MPL. The significance of these findings to the use of MPL as an immunological adjuvant or an immunomodulating agent is discussed.

T-cell modulation of the murine antibody response to Neisseria meningitidis group A capsular polysaccharide

T-cell modulation of the antibody response of BALB/c mice to group A meningococcal capsular polysaccharide (PS) was examined by using an enzyme-linked immunosorbent assay. An optimal dose (5 micrograms) of antigen induced an immunoglobulin M (IgM) response of short duration; no IgG or IgA antibody could be detected. The capacity to produce serum antibody begins at about 3 weeks of age. Concanavalin A (ConA) inhibited the magnitude of the response by 40 to 60% when given at the time of immunization; it enhanced the response two- to eightfold when given 2 days after PS. T-cell-mediated suppression could be transferred to naive mice by injection of spleen cells from low-dose-primed mice. A secondary antibody response could be induced by immunization with live meningococci. Here, the IgM response was 8- to 10-fold greater than that of mice given an optimal dose of PS; IgG antibody against group A PS increased 1 week after immunization to levels that were 100- to 1,000-fold greater than those of mice immunized with PS. The antibody response could not be augmented by multiple injections of PS; suppression occurred after low-dose priming or hyperimmunization with PS. These studies indicate that the antibody response to PS is not completely T-cell independent; rather, it is inhibited and amplified by T cells.

Functional analysis of T-cell subsets in chronic experimental alcoholism

In order to obtain a better understanding of immune system function in chronic alcoholism, we have assessed primary B-cell responses to helper T-cell independent (TI) and dependent (TD) antigens in chronic alcoholic Sprague-Dawley male rats fed totally liquid diet containing ethanol. Pair-fed littermates received the same diet except that carbohydrates isocalorically replaced ethanol, which accounted for 36% of the total calories. The ability of alcoholic animals to mount primary in vivo splenic plaque-forming cell (PFC) responses to TI pneumococcal polysaccharide type III (SIII) was elevated throughout 50 days of observation when compared to pair-fed controls; serum antibody responses to SIII paralleled the enhanced PFC responses. Primary in vivo B-cell responses to antigen sheep red blood cells (SRBC), a TD antigen, were initially elevated but were found to be significantly suppressed 30 days after chronic ethanol consumption. The degree of immunosuppression increased with length of chronic ethanol consumption. The elevated primary splenic PFC responses to TI (SIII) may be attributed to loss of T-suppressor cell control, since alcoholic rat spleen cells did not respond to low-dose priming with SIII. We suggest that either loss of function and/or actual depletion of accessory and regulatory cells (T-suppressor and T-helper) may be responsible for irregularities in B-cell function observed during chronic alcoholism. T-cell subset enumeration using fluorescein-labelled monoclonal antibodies revealed that a sequential T-helper and T-suppressor loss occurred several days following dysfunction of these T-cell subsets in splenic populations, suggesting that a combination of numerical and dysfunctional changes in lymphocyte subpopulations may be responsible for the immunological alterations observed in chronic alcoholics.

Effect of Fluosol DA 20% on antibody response to type 3 pneumococcal polysaccharide in rats

Exchange transfusion with the oxygen-carrying resuscitation fluid, Fluosol DA 20% (FDA), interferes with the efficacy of penicillin therapy of pneumococcal infection in rats. Because this effect could not be attributed to an interaction between FDA and penicillin, the effect of FDA on the ability of rats to mount an antibody response to type 3 pneumococcal polysaccharide was tested. FDA (25 ml) was administered by isovolumetric exchange transfusion. Rats were immunized intravenously with 0.2 microgram of type 3 pneumococcal polysaccharide 3 days before, 1 day before, 1 day after, or 3 days after transfusion with FDA. IgM and IgG antibody responses were determined by ELISA 0, 3, 7, 10, 14, 21, and 28 days after immunization. When rats were immunized 3 days before or 1 day before transfusion with FDA, antibody levels were increased above control levels and remained relatively high through Day 28. When the animals were immunized 1 day after transfusion, antibody levels were approximately the same as in the control group. When the rats were immunized 3 days after transfusion, antibody levels were suppressed. These data suggest that FDA does not inhibit the humoral immune response when administered after or within 1 day before immunization, but does inhibit the response when immunization is given 3 days after transfusion.

Natural killer cell regulation of age-related and type-specific variations in antibody responses to pneumococcal polysaccharides

Pretreatment of mice with anti-asialo GM1, which has been shown to deplete NK cytolytic activity without affecting cytotoxic T cells or macrophages, increased the weak anti-PPS 6 responses of adult mice to levels similar to that of their anti-PPS 3 responses, and increased the weak-to-absent anti-PPS 3 and anti-PPS 6 responses of weanling mice to the same levels as achieved by adult mice. By contrast, pretreatment with poly(IC), which augments NK activity, resulted in a 14-fold reduction in the anti-PPS 3 responses of adult mice. The enhancement of anti-PPS responses in mice treated with anti-asialo GM1 was due to inactivation or depletion of NK cells, and not T suppressor cells, since this enhancement occurred in athymic nude mice as well as in euthymic mice. In addition, strains of mice with low or absent endogenous NK activity were found to have considerably stronger anti-PPS responses than strains of mice with normal NK activity. NK depletion enhanced anti-PPS 6 IgM but not IgG response, and resulted in a true increase in antibody production rather than an alteration in the time course of the response. These findings indicate that NK cells physiologically downregulate anti-PPS responses, and that age-dependent and type-specific variations in these responses are primarily determined by NK regulatory effects.

Studies of immune responses in mice prone to autoimmune disorders. II. Decreased down-regulation by auto-anti-idiotype antibody in autoimmune-prone mice

Three lines of evidence are presented which suggest that autoimmune-prone mice are deficient in the production of auto-anti-idiotype antibody during their immune response to trinitrophenylated Ficoll (TNP-F). NZB, MRL lpr/lpr and older BXSB male mice have no hapten-augmentable plaque-forming cells (PFC). Hapten-augmentable PFC have been previously shown to be cells whose secretion of antibody has been inhibited by the binding of auto-anti-idiotype antibody to cell surface idiotype. Sera from TNP-F immunized NZB mice lack PFC inhibiting activity (anti-idiotype antibody). Spleen cells from TNP-F immune NZB mice fail to transfer anti-idiotype antibody-mediated suppression to naive mice as do spleen cells from immune non-autoimmune-prone mice. Taken together these data suggest that autoimmune-prone mice are deficient in auto-anti-idiotype antibody-mediated downward regulation of their immune responses. It was further shown that the immune response of NZB mice to TNP-F shows a slower decline in splenic PFC and a greater heterogeneity of PFC affinity than do the responses of non-autoimmune-prone strains. Since athymic (nude) mice, which were previously shown to be defective in the production of auto-anti-idiotype antibody, also show a slower decline in splenic PFC and an increased heterogeneity of PFC affinity, it is suggested that these peculiarities of the immune responses of autoimmune-prone and athymic mice are also the consequences of the lack of auto-anti-idiotype antibody-mediated down-regulation.

T lymphocyte-mediated protection against Pseudomonas aeruginosa infection in granulocytopenic mice

BALB/c mice immunized with Pseudomonas aeruginosa immunotype 1 polysaccharide develop protective T cell immunity to bacterial challenge. In vitro, T cells from immunized mice kill P. aeruginosa by production of a bactericidal lymphokine. The present study demonstrates that adoptive transfer of T cells from immunized BALB/c mice to granulocytopenic mice resulted in 97% survival on challenge with P. aeruginosa, compared with 17% survival with adoptive transfer of T cells from nonimmune BALB/c mice. This protection is specifically elicited by reexposure to the original immunizing antigen; adoptive recipients cannot withstand challenge with immunotype 3 P. aeruginosa. However, the adoptive recipients do survive simultaneous infection with both P. aeruginosa immunotypes 1 and 3. Adoptive transfer of T cells from the congenic CB.20 mice, which are unable to kill P. aeruginosa in vitro, provides only 20% protection to granulocytopenic mice. These studies indicate that transfer of specific immune T lymphocytes can significantly enhance the resistance to P. aeruginosa infection in granulocytopenic mice.

The immune response to pneumococcal polysaccharide type III is followed by increased production of an antibody antifactor

The study shows that serum from pneumococcal polysaccharide type III (SSSIII)-immunized and nonimmunized mice that has been absorbed until devoid of anti-SSSIII antibodies inhibits anti-SSSIII plaque-forming cells (PFC) but not antisheep red blood PFC in antibody plaque assay. A large fraction of the inhibitions activity can be absorbed by and eluted from anti-SSSIII-Sepharose, but not normal mouse serum-Sepharose. It has low or no affinity for protein A and concanavalin A. The titre of the inhibitor increases with repeated immunizations and inhibits the anti-SSSIII PFC of rats or mice of different allotypes. On the basis of these characteristics, I classify the inhibitor as an anti-idiotypic nonimmunoglobulin factor directed against a common determinant of anti-SSSIII antibodies of mouse and rat, with an immuno-regulatory function.

Quantitation of blood lymphocytes secreting antibodies to pneumococcal polysaccharides after in vivo antigenic stimulation

An indirect plaque-forming cell assay detecting B cells secreting IgM, IgG and IgA antibodies against pneumococcal polysaccharides (PPS) is described. The numbers of anti-PPS-secreting cells (SC) and Ig-SC in the blood of normal persons immunized with a polyvalent PPS vaccine were quantitated. Anti-PPS-SC were recorded from the fourth to the twelfth post-vaccination day, and the maximum number was found between days 6 and 9. Quantitatively IgA anti-PPS-SC outnumbered the IgM and IgG anti-PPS-SC. Concomitant with the increase in the numbers of antibody-SC an increase in polyclonally activated IgM-, IgG- and IgA-SC was recorded. The specific anti-PPS-antibody-SC constituted 20-80% of the total numbers of Ig-SC from the sixth to the ninth post-vaccination day.

The role of antigen in the activation of regulatory T cells by immune B cells

The transfer of B cells from mice immunized with Type III pneumococcal polysaccharide (SSS-III) results in the activation of suppressor and amplifier T cells that control the magnitude of the antibody response in recipient mice, immunized subsequently with SSS-III. Prior treatment of transferred B cells with an excess of enzyme (polysaccharide depolymerase) capable of hydrolyzing SSS-III, does not alter the capacity of these cells to activate regulatory T cells. These findings indicate that the activation of regulatory T cells by immune B cells is not mediated by residual antigen on the surface of transferred cells.

Lymphocyte function in experimental endemic syphilis of Syrian hamsters

We have studied the changes in the lymph nodes, spleen and thymus that occur in inbred LSH Syrian hamsters infected with Treponema pallidum Bosnia A, the causative agent of endemic syphilis, as well as the B-cell responses of these infected animals to helper T-cell independent and dependent antigens. The lymph nodes increased significantly in weight up to 6 weeks after infection, and contained viable treponemes. No significant changes in the spleen weight were observed, and no viable treponemes could be recovered from the spleen. However, the size of the thymus decreased steadily during the course of the disease. The relative number of Ig+ cells (B cells) increased in the spleen and regional lymph nodes, whereas the relative number of T cells decreased during the course of infection. In both the spleen and lymph nodes, the relative number of macrophages increased initially and decreased thereafter in the form of a bell-shaped curve showing a peak at 4-6 weeks of infection. The ability of splenic lymphocytes from infected hamsters to mount a primary PFC response to pneumococcal polysaccharide type III (SIII), a helper T-cell independent antigen, was elevated throughout the course of infection. However, the splenic PFC response to sheep erythrocytes (SRBC), a helper T-cell dependent antigen, was increased only during the first 4 weeks of infection and progressively decreased thereafter. The PFC responses of infected lymph node lymphocytes to both SIII and SRBC were increased during the first 4 weeks and decreased thereafter. These data suggested that atrophy of the thymus seen in syphilitic infection is accompanied by the complex losses of subsets of T cells and altered B-cell functions. An early loss of suppressor T cells in both the lymph nodes and spleen occurs concomitantly with a loss of T helper cells and heterologous (treponema-unrelated) B-cell functions in the lymph nodes. Helper T cells are lost from the spleen only in the later stages of infection, whereas splenic B-cell functions remain intact throughout the course of the disease. These findings were further tested by in vitro methods where splenic and lymph node lymphocytes from infected hamsters were examined for their ability to respond to Con A in terms of the induction of antigen non-specific suppressor T cells. The mixing of Con A stimulated splenic or lymph node lymphocytes from infected hamsters was unable to inhibit the primary antibody responses of SRBC as compared to the normal control.(ABSTRACT TRUNCATED AT 400 WORDS)

Amplifier T cell activity is decreased in MRL/1 mice: failure of concanavalin A and anti-lymphocyte serum to enhance antibody responses to thymus-independent antigens

In order to indirectly assess T and B cell function in vivo in spontaneously autoimmune MRL mice, IgM plaque forming cell (PFC) responses to the thymus-independent antigens type III pneumococcal polysaccharide (S3) and polyvinylpyrrolidone (PVP) were determined. Both MRL/Mp-lpr/lpr (MRL/l) and MRL/Mp+/+ (MRL/n) mice responded well to S3 and, in fact, low doses of S3 which are not immunogenic in normal strains of mice elicited good responses in MRL mice. PVP was less immunogenic than S3, however, doses of PVP which are considered sub-immunogenic in normal mice did elicit responses in MRL mice. The effect of ageing on S3 and PVP responsiveness in MRL mice was also determined. Responses to S3 and PVP declined minimally in MRL/l mice and were unchanged in MRL/n mice. Amplifier T cell (TA) activity in MRL mice was indirectly assessed by determining the effect on concanavalin A or anti-lymphocyte serum on PFC responses to S3 and PVP. Whereas significant enhancement of the S3 and PVP IgM PFC responses occurred in MRL/n mice, neither method elicited remarkable enhancement in MRL/l mice. The lack of IgM enhancement was not due to altered kinetics of activation nor to a switch to IgG PFC responses. Possible reasons for the apparent dysfunction of TA in MRL/l mice are discussed.

Immune response of mice exposed to cis-diamminedichloroplatinum

The effects of cis-diamminedichloroplatinum (CDDP) on lymphoid organs and the immune response of young and older adult mice were studied histologically and by functionally assessing the activity of various subpopulations of immune cells. Young adult mice (6-8 weeks old) treated with 2 mg/kg CDDP mounted an enhanced splenic plaque-forming cell (PFC) response to both sheep erythrocytes, a helper T-cell-dependent antigen (HD), and pneumococcal polysaccharide type III a helper T-cell-independent antigen (HI). Older adult mice (18-22 weeks old) treated in the same way exhibited an equally enhanced PFC response to HD antigen and even a more pronounced response to HI antigen. Treatment of mice with 12 mg/kg CDDP resulted in immunosuppression. Thymus, lymph nodes, and spleen of animals treated with the higher dose of CDDP showed a marked cell depletion from both T and B areas, confirming that the immunosuppression was due to an indiscriminate elimination of both T and B lymphocytes. The immunosuppression and the cell depletion from lymphoid organs were more pronounced in younger mice. Thus, the effects of CDDP on the lymphoid organs and the immune response depend both on the age of the animals and on the dose of the drug. CDDP given in small doses enhances the PFC response, whereas a reduced PFC response is obtained following high-dose treatment.

Depletion of T lymphocyte population in pneumococcal infection

T lymphocyte population in absolute numbers and percentage is decreased during the course of pneumococcal infection in Nigerians and may explain, to some extent, the frequent complication of herpes labialis.

Regulation of the antibody response to type III pneumococcal polysaccharide by contrasuppressor T cells

A soluble membrane component of type III pneumococcal polysaccharide-coupled spleen cells (S3-SCSM) induces S3-specific suppressor T cells (Ts) in mice. These Ts can be detected only if mice are pretreated with cyclophosphamide (Cy) or if cells adherent to the lectin Vicia villosa are removed from the spleen cell population prior to transfer. The V. villosa-adherent spleen cells from mice injected with S3-SCSM could abrogate suppression mediated by Ts induced by S3-SCSM in Cy-treated mice. The V. villosa-adherent contrasuppressor cells were shown to be T cells that were I-J+ and of the Lyt-1 phenotype. Contrasuppressor T cells (Tcs) were not present in V. villosa-adherent spleen cell fractions obtained from normal mice, from mice injected with polyvinylpyrrolidone-coupled spleen cells, or from Cy-treated mice injected with S3-SCSM, i.e., mice in which Ts activity is dominant. The V. villosa-adherent cells that abrogated the activity of Ts induced by S3-SCSM in Cy-treated mice did not abrogate suppression mediated by a different subset of S3-specific Ts, suggesting that the Tcs described here do not have activity against all Ts subsets. The ability of S3-SCSM to activate Tcs in normal mice provides an explanation for the inability to detect S3-specific Ts in several previous studies.

Genetic control of the murine IgM plaque-forming cell response to type III pneumococcal polysaccharide

The direct 5-day plaque-forming cell response of different inbred mouse strains to pneumococcal polysaccharide type III (SSS-III) varied from more than 10,000 per spleen, in BALB/c mice, to less than 2000 in C57BL mice. Responses of Igh congenic and recombinant inbred lines bearing different combinations of BALB/c and C57BL genes indicate that two or more gene loci are involved in controlling high or low responses. At least one is in the Igh-V region since BALB/c, BAB-14, and CB-8 KN mice (Igh-Va) had two to four times higher responses than CB-20 and CB-16 KN mice (Igh-Vb). Other gene loci must be involved, but nothing can be said about them at present.

Activation of antigen-specific suppressor T cells by B cells from mice immunized with type III pneumococcal polysaccharide

The transfer of B lymphocytes from mice immunized with type III pneumococcal polysaccharide (SSS-III) results in antigen-specific suppression of the antibody response of recipients immunized with SSS-III. Such suppression shares many features associated with low-dose paralysis, a phenomenon mediated by suppressor T cells; it reaches maximal levels 3 d after the transfer of viable or irradiated immune B cells and can be eliminated by the depletion of SSS-III-binding cells from spleen cell suspensions before transfer. In a two-step cell transfer experiment, purified T lymphocytes, isolated from recipients previously given immune B cells, caused suppression upon transfer to other mice immunized with SSS-III. Also, B-cell-induced suppression could be abrogated in a competitive manner by the infusion of amplifier T lymphocytes, as was previously demonstrated in the case of low-dose paralysis. These findings suggest that B cell surface components, presumably the idiotypic determinants of cell-associated antibody specific for SSS-III, are instrumental in activating suppressor T cells involved in regulating the magnitude of the antibody response to SSS-III.

Role of T-lymphocytes in production of antibody to antigens of Rickettsia tsutsugamushi and other Rickettsia species

The requirement of thymus-dependent lymphocytes for antibody production to Rickettsia tsutsugamushi, Rickettsia akari, Rickettsia conorii, and Rickettsia typhi was investigated by comparing antibody production in athymic (nu/nu) or thymus-bearing BALB/c mice. Athymic BALB/c mice produced antibody after infection with R. akari, R. conorii, and R. typhi as measured by indirect fluorescent antibody titration or radioimmunoassay. Antibody production in these mice was a great or greater than in the thymus-bearing mice and demonstrated similar kinetics. In contrast, athymic BALB/c mice infected either intraperitoneally or subcutaneously with the Gilliam strain of R. tsutsugamushi failed to produce demonstrable antibody. The requirement of thymus-dependent lymphocytes for antibody production to R. tsutsugamushi was further suggested by the demonstration of antibody production after transfer of immune thymus-dependent lymphocytes to athymic mice and the demonstration of R. tsutsugamushi-specific T helper cells in immune thymus-bearing mice. The antibody produced in athymic mice after infection with R. akari, R. conorii, and R. typhi was predominantly immunoglobulin M, based on isotype-specific radioimmunoassays and sucrose gradient fractionation. Furthermore, the antibody produced by athymic mice in response to R. akari infection reacted with a carbohydrate-containing outer membrane component.

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.

Characterization of a concanavalin A-induced amplifier T cell which augments in vitro antibody responses to DNP-Ficoll

The addition of the T-cell mitogen concanavalin A (Con A) on Day 2 of a 4-day in vitro culture of murine spleen cells with the thymus-independent (TI) antigen DNP39-Ficoll resulted in significant enhancement of the direct antitrinitrophenyl (TNP) plaque-forming cell (PFC) response. This enhancement was mediated by a nylon wool- and antiimmunoglobulin-nonadherent amplifier T cell (TA). TA activity was not eliminated by in vitro treatment of T cells with anti-Thy 1.2 and complement (C). TA activity could be eliminated by pretreatment of mice with antilymphocyte serum (ALS) in vivo, followed by in vitro treatment of T cells with anti-Thy 1.2 + C. Thus, TA appear to bear a low surface density of Thy-1 antigen. These TA were relatively resistant to ALS used alone, to cyclophosphamide, and to low dose in vitro irradiation. TA were still present in the spleen 14 weeks after adult thymectomy (ATx). They were I-J positive and apparently belonged to the Lyt 1+2- T-cell subset.

Characterization of the murine immune response to type 6 pneumococcal polysaccharide

The antibody response to type 6 (Danish type 6A) pneumococcal capsular polysaccharide (S6) was determined in various strains of mice. S6 elicited a very low plaque-forming cell (PFC) response in most strains of mice. BALB/c mice responded better than most other strains, and the response to S6 was further characterized in BALB/c mice. Immunization with 1 to 5 micrograms of S6 induced a plaque-forming cell response of short duration which consisted totally of immunoglobulin M-producing PFC. Athymic nude mice produced three- to fivefold more PFC in response to S6 than their euthymic littermates, suggesting that thymus-derived (T) cells negatively influence the S6 response. Regulation of the response by T cells was further suggested by the ability of antilymphocyte serum to enhance the S6 PFC response and by the suppressed response induced by priming with a low dose of S6 3 days before immunization with an optimal dose of S6 (low dose paralysis). When concanavalin A was given 2 days after immunization with S6, the response was enhanced two- to sevenfold, suggesting that the response is also positively influenced by T amplifier cells. When the avidity of the antibody produced by S6-specific PFC was measured by a plaque inhibition test, the avidity of the anti-S6 antibody was found to be very low. These results suggest that S6 is a poor immunogen because the affinity of the S6-specific antibody and B cell surface receptors is low.

Patterns of isotype expression by B cell clones responding to thymus-dependent and thymus-independent antigens in vitro

It was found that the Type 2 thymus-independent (TI-2) antigens bacterial levan, trinitrophenyl-Ficoll, and pneumococcal carbohydrate vaccine (PnC) stimulate clonal expansion and antibody secretion in splenic fragments from either hemocyaninprimed or unprimed irradiated recipients bearing B cells from unprimed donors. The in vitro stimulation with TI-2 antigens leads to the expression of isotype switching and provides a more balanced variety of isotypes than is usually observed in vivo. Still, some characteristic patterns of isotypes expressed in vivo to either TI-2 or thymus-dependent (TD) antigens are preserved in vitro. Frequencies of phosphocholine (PC)-reactive B cells responding to either PnC or to PC-hemocyanin (PC-Hy) suggest an appreciable overlap in populations responding to these TI and TD forms of antigen. The existence of a population responsive to either form of PC determinant is supported by the observation that many clones arising in the presence of both forms of antigen express patterns of isotypes that appear as summations of those distinct patterns shown by clones responding to only one form or the other. These data suggest that PC-Hy- and PnC-responding cells may derive from a linear rather than a branched pathway of B cell development and that expression of isotype switching over the lifetime of a developing B cell clone may be regulated in a manner dependent on the form of the stimulating antigen.

Detection of plaque-forming cells by a latex bead technique

A new latex bead technique for measuring the plaque-forming cell (PFC) responses to bacterial antigens is described. This technique has been designed for the study of antigens that cannot be readily coated onto SRBC but may also used for antigens that adsorb onto SRBC as well. Application of the latex based technique for the study of PFC response of hamsters to Treponema reiter antigen is described in detail. Using SIII, an antigen that readily adsorbs to SRBC, we have compared the latex bead technique and the conventional SRBC-PFC technique and found that the latex bead technique is more sensitive than the conventional technique. The technique can be used for direct and indirect PFC assays. Technical details for the optimal performance of the latex bead PFC assay are outlined.