Regulation of the antibody response to type III pneumococcal polysaccharide. V. Ontogeny of factors influencing the magnitude of the plaque-forming cell response.

Mice of different ages were evaluated with respect to their ability to give a plaque-forming cell (PFC) response to Type III pneumococcal polysaccharide (SSSIII), as well as the degree of amplifier and suppressor thymus-derived(T) cell activity present. Although the magnitude of the PFC response to an optimally immunogenic dose of SSS-III for 2-and 3-week old mice was only 7% and 14%, respectively, of that produced by adult (8-week old) mice, values comparable to those of adult animals were attained by 4 weeks of age; no significant changes in the ability to respond to SSS-III occurred thereafter. Amplifier T cell activity, which was minimal at 2 to 4 weeks of age, matured slowly and did not reach a maximum until 8 to 10 weeks of age. By contrast, suppressor T cell activity appeared to be fully developed at least as early as 2 weeks of age; here, the inhibitory effects produced could by abrogated by depletion of T cells, indicating that the unresponsiveneness induced by such cells does not result in the depletion ot irreversible inactivation of B cells capable of responding to SSS-III. These findings suggest that the inhibitory effects of suppressor T cells are predominant in young mice and that such cells may play an important role in determining the ease with which unresponsiveness is induced in neonates, and in the prevention of autoimmune disease. Also, studies conducted with adult-thymectomized mice showed that both amplifier and suppressor T cells, once seeded to the periphery, are stable and do not depend upon the presence of intact thymus for the expression or renewal of their activity.     

Genetic regulation of the antibody response to H-2Db alloantigens in mice

The cytotoxic antibody response to the H-2D^b alloantigen has been investigated in ten strains of the C57BL/10 background. Three types of responses could be distinguished: no detectable response, an IgM response, and an IgG response. The IgG response is influenced by the D and probably the I-A region of the H-2 complex, whereas the IgM response is dependent on the allele for the E chain. The hypothesis is proposed that regulatory T cells, which recognize the antigen in context of self MHC molecules, determine the outcome of an anti-H-2D^b immunization in which the I-E molecule restricts the IgM response and the I-A molecule restricts the IgG response; the D molecule is probably responsible for activation of suppressor T cells which suppress only the IgG response.     

Regulation of idiotope expression. I. The effect of antigen dose on expression of certain T15 idiotopes during primary IgM response to S. pneumoniae R36a

Clonal heterogeneity among B cells reactive to the same epitope may be determined through differences in idiotypy. It appears that clones bearing distinct idiotopes may constitute functionally distinct subpopulations. Data suggest that idiotopically distinct clones of PC-reactive B cells may be regulated independently of one another. We have looked to see whether individual T15+ clones may also differ in their requirements for activation. Here we examine the effect of immunizing doses of antigen on expression of two T15 idiotopes, B36-82 and B39-38, during both in vivo and in vitro primary responses to Streptococcus pneumoniae R36a (Pn) in CB-20 mouse strain. The idiotopes were detected on the specific antibody plaque-forming cells (PFC) by using monoclonal anti-idiotopic antibodies. We find that distinct patterns of idiotope expression are generated by stimulation with different doses of antigen. Immunization with suboptimal and super-optimal doses of Pn produced responses dominated by PFC expressing both idiotopes, whereas PFC induced by optimal antigen concentrations were primarily B36-82+ and B39-38-. These data indicate that the varying of antigen concentration may induce the response of different B cells bearing distinct idiotypes.     

Genetics of resistance to the African trypanosomes. III. Variant-specific antibody responses of H-2-compatible resistant and susceptible mice

Genetically based differences in variant-specific immunity to the African trypanosomes were examined. H-2-compatible inbred mouse strains that differed in relative resistance were infected with Trypanosoma rhodesiense clone LouTat 1. Antibody responses to exposed epitopes of the LouTat 1 variant-specific surface glycoprotein (VSG) were measured. Relatively resistant B10.BR mice (H-2k) made predictable IgM antibody responses to the VSG of LouTat 1 which were associated with clearance of the LouTat 1 variant antigenic type from blood; IgG responses to LouTat 1 surface antigen appeared after clearance occurred, and were lower than peak titers of IgM. Intermediately susceptible CBA mice (H-2k) also made predictable IgM and IgG responses which followed the same pattern as the more resistant strain. Peak titers were lower for both Ig classes, however, and a delayed appearance of antibody was correlated with delayed clearance of LouTat 1. In contrast to B10.BR and CBA mice, the susceptible C3H mice (H-2k) failed to make detectable antibodies to LouTat 1 surface antigen and also failed to control the first peak of parasitemia. The absence of immunity in infected C3H mice was selective for antibody to exposed epitopes of LouTat 1 VSG because antibody was detectable to invariant VSG or internal trypanosome antigens. Also, the C3H strain was shown not to be a genetic nonresponder to LouTat 1 surface antigen because VSG-specific antibodies appeared within 1 wk after trypanocidal chemotherapy. Finally, we demonstrated that the susceptibility of C3H mice was not associated with an inability of the mononuclear phagocyte system to clear the parasites because drug cure, passive transfer of immune serum, or sensitization of trypanosomes with antibody all led to trypanosome clearance from blood by the liver. In summary, we show for the first time that major differences in variant-specific immunity occur in MHC-compatible animals after infection with the African trypanosomes.     

Analysis of anti-streptococcal group A carbohydrate idiotope levels in sera: correlation of magnitude of expression with idiotope position and VK haplotype

We have employed monoclonal anti-idiotopes to map the corresponding idiotopes on the variable domain of a prototype antibody specific for streptococcal group A carbohydrate (GAC). Idiotope variability, as assessed by direct and competitive binding assays, previously was shown to correlate with idiotope position; determinants farther from the binding site were less variable. We now describe a relationship between idiotope position and idiotope concentration in normal and GAC-immune sera from mice of several inbred and recombinant inbred strains. Employing sera as inhibitors in a competitive radioimmunoassay, we demonstrate that idiotopes farther from the binding site (more proximal) tend to be present at higher levels in GAC-hyperimmune sera. Only the most proximal idiotope was detected in normal serum, and this idiotope was present in normal sera from all 12 strains tested. Finally, significant interstrain differences in patterns of idiotope expression were observed, and some of these differences appear to be correlated with allelic differences at immunoglobulin structural gene loci.     

Complementary idiotypy in the regulation of the immune response.

A new concept is presented for the interactions of two complementary antibodies in the immune response. These antibodies bind to each other by means of their variable sequence determinants and therefore are designated as complementary idiotypes. Under certain conditions, both complementary idiotypes are produced by the same animal at the same time. An idiotype can drastically affect the expression of the complementary idiotype in the animal, inducing a peripheral quench effect of antibody-binding activity and a central effect on the immunocompetent cell, which produces the complementary idiotype. It is proposed that complementary idiotypes might be induced during every immune response, thus playing an essential role in the regulation of the immune response.     

Negative segregation of Mtv loci in H-2E + mice selected for high antibody response

Endogenous mouse mammary tumor proviruses (Mtvs) encode superantigens (Sags), which can delete T lymphocytes expressing particular Tcrb-V genes when associated with the H-2E molecule. In the present work, distribution of Mtvs was investigated in six independent pairs of mouse lines genetically selected for high (H) or low (L) Ab production to specific T-cell-dependent Ags. These experiments were performed to evaluate the role of Mtv-encoded Sags in the determination of H and L phenotypes. No systematic difference is observed in Mtv segregation between H-2E– H and L mouse lines. However, a clear differential segregation of Mtv loci is observed between H-2E+ H and L mice from three independent selections. The number of endogenous Mtvs in L lines is close to that found in laboratory mice. In contrast, Mtv loci-encoding Sags are almost absent in H animals. Although Sags profoundly affect the available Tcrb-V repertoire in H-2E+ L mice, it seems unlikely that Mtvs account for the L phenotype which can be achieved independently of Mtv segregation in H-2E– lines. More importantly, the results suggest that negative segregation of Mtv-encoding Sags contribute to determine the super-responder phenotype of H lines.     

Intra-H-2 recombination in the mouse. III. I-Region characterization of haplotypes H-2at2, H-2at3 and H-2a2

Serological characterization of three K-S interval recombinant strains, TBR2 (H-2at2), TBR3 (H-2at3) and AIR 1 (H-2a2) was performed using anti-H-2, Ia, Ss and Slp antisera. The data presented here reveal that the crossover events in both TBR2 and TBR3 occurred between the I-A and I-E subregions. In both cases, the H-2K and I-A subregions were derived fron the H-2t1 of chromosome, while the I-E, S and H-2D regions were derived from the H-2b chromosome (KsAkEbSbDb). The H-2a2 chromosome resulted from a crossover event between the H-2a1 and H-2i9 chromosomes. Ia and Ss typing of AIR 1 suggested that the K to I-E regions originated from H-2a1 and the S and D regions originated from H-2i9 (KkAkEkSbDd).     

Assessment of the role of determinant selection in genetic control of the immune response to insulin in H-2b mice.

The immune response to insulin is regulated by MHC class II genes. Immune response (Ir) gene-linked low responsiveness to protein Ags can be mediated by the low affinity of potential antigenic determinants for MHC molecules (determinant selection) or by the influence of MHC on the functional T cell repertoire. Strong evidence exists that determinant selection plays a key role in epitope immunodominance and Ir gene-linked unresponsiveness. However, the actual measurement of relative MHC-binding affinities of all potential peptides derived from well-characterized model Ags under Ir gene regulation has been very limited. We chose to take advantage of the simplicity of the structure of insulin to study the mechanism of Ir gene control in H-2b mice, which respond to beef insulin (BINS) but not pork insulin (PINS). Peptides from these proteins, including the immunodominant A(1-14) determinant, were observed to have similar affinities for purified IAb in binding experiments. Functional and biochemical experiments suggested that PINS and BINS are processed with similar efficiency. The T cell response to synthetic pork A(1-14) was considerably weaker than the response to the BINS peptide. We conclude that the poor immunogenicity of PINS in H-2b mice is a consequence of the T cell repertoire rather than differences in processing and presentation.     

H-2 haplotype and sex-related differences in IgG response to ovalbumin in mice.

Specific IgG antibodies were determined by enzyme-linked immunosorbent assay (ELISA) in 7 strains of male and female mice after immunization with ovalbumin. Also, H-2 haplotype and sex-related differences in IgG response to ovalbumin were evaluated using statistical methods, slope ratio assay and parallel line assay. H-2k strain mice (C3H/HeN and CBA/JN) showed higher IgG responsiveness to ovalbumin than H-2d (BALB/cAnN and DBA/2 N) and H-2b (C57BL/6 N) mice. With regard to the sex-related differences in IgG response to ovalbumin, females in some strains showed higher IgG response than males, but some strains showed no sex-related differences, and sex-related differences in IgG response to ovalbumin did not relate to their H-2 haplotypes. These results may be caused by other immune response genes which control the sex-related immune response than H-2 or other unknown factors.     

Regulation of antitubercular immunity in mice by genes of the H-2 complex

Development of DTH reaction and survival time after M. tuberculosis H37Rv infection have been studied in H-2 congenic and recombinant mice pretreated with high doses of BCG vaccine. In addition, in vitro proliferation of lymphocytes from infected CBA, B6 and 4R mice to PPD was studied in the presence of anti-I-A and anti-I-E mAbs. High doses of BCG vaccination (1 mg/mouse) have led to a significant inhibition of DTH and diminution of survival time in B10.M (H-2f) mice only, and to opposite effects in all other strains tested (H-2a, b, d, k, h4). In I-A+, I-E- 4R mice anti-I-Ak mAbs abrogated lymphocyte proliferation to PPD completely, while in I-A+, I-E- CBA mice only the mixture of anti-I-Ak and anti-I-Ek mAbs was effective.     

Monoclonal antibody reveals H-2-linked quantitative and qualitative variation in the expression of a Qa-2 region determinant

We have produced a monoclonal antibody, Y-7, that reacts with a Qa-2 region-controlled determinant. Cellular and strain distribution analyses, coupled with quantitative variation in the amount of Y-7 antigen expressed among strains, provide overwhelming evidence that Y-7 reacts with the Qa-2^a determinant. The determinant detected by Y-7 is differentially expressed in T and B lymphocytes in a strain specific manner. Y-7 reacts with the majority of T lymphocytes (> 95%) and approximately one-half of B lymphocytes in certain strains (++ strains), and with the majority of T lymphocytes (> 95%) and no B lymphocytes in other strains (+ strains). T lymphocytes in + strains express approximately three fold less of the Y-7 determinant than T lymphocytes from ++ strains. In addition, we show that the Y-7 determinant is expressed in approximately one-third to one-half of Lyb-3^?, 5^? B lymphocytes. Possible mechanisms determining quantitative and qualitative variation in the expression of the Y-7 determinant in T and B lymphocytes are discussed.     

Selective sensitivity to hydrocortisone of regulatory functions that determine the magnitude of the antibody response to type III pneumococcal polysaccharide.

Previous studies on the basis for the immunosuppressive potential of adrenal corticosteroids have stressed that the effects of these agents on immune functions depend on the animal species being considered, as well as the subpopulations of lymphocytes involved in the expression of immune functions examined. In the present work, we have evaluated the effect of a single dose of hydrocortisone on three different immunoregulatory functions that can influence the magnitude of an antibody response to Type III pneumococcal polysaccharide (SSS-III) in mice; these functions include suppressor, amplifier, and helper activity that are dependent upon the presence of distinct subpopulations of thymus-derived (T) cells. The results obtained show that a single injection of a relatively large dose of hydrocortisone, when given at the time of priming with carrier, eliminated all evidence of carrier-specific helper T cell activity; hydrocortisone was also found to eliminate a significant amount of helper T cell activity when given after such activity had been generated. But, under the same experimental conditions, suppressor and amplifier T cell activities were unaffected, even in this steroid-sensitive species. Such selective sensitivity may account for some of the immunosuppressive potency of steroids.     

Idiotype-specific T lymphocytes. I. Regulation of antibody production by idiotype-specific H-2-restricted T lymphocytes

Cytotoxic T lymphocytes (CTL) specific for MOPC-104E myeloma cells of BALB/c origin could be induced in BALB/c, (BALB/c X BALB.B)F1, and (BALB/c X BALB.K)F1 mice. (BALB/c X BALB.B)F1 CTL activity specific for MOPC-104E was effectively inhibited by anti-H-2d but not by anti-H-2b alloantiserum. However, the activity was hardly blocked by specific anti-idiotypic antibodies to MOPC-104E. For further analysis of the recognition of idiotype on target cells by CTL, the effect of those lymphocytes on anti-dextran B1355S antibody-producing B lymphocytes, which have a cross-reactive idiotype to MOPC-104E, was investigated. Lymphocytes from the CTL population did inhibit antibody production by dextran-immune spleen cells, but those from the CTL population specific for irrelevant myeloma cells (MOPC-167) did not. The (BALB/c X BALB.K)F1 CTL population suppressed the antibody production of BALB/c but not of BALB.K. This indicates that F1 cells can preferentially see H-2 antigens of immunizing myeloma cells on target B lymphocytes. The inhibition of antibody production was antigen specific and was only restricted to the PFC that were inhibitable by anti-idiotypic antibodies. The surface phenotypes of the cells that inhibited the antibody production were Thy-1+, Lyt-1-, Lyt-2+, and I-J-. These results strongly suggest that CTL specific for MOPC-104E recognize self H-2 antigens simultaneously with idiotypic determinants on B lymphocytes. Possible immunoregulatory roles of idiotype-specific CTL on antibody production systems are also suggested.     

Host genetic background affects regulatory T-cell activity that influences the magnitude of cellular immune response against Mycobacterium tuberculosis

Using two mouse strains with different abilities to generate interferon (IFN)-γ production after Mycobacterium tuberculosis infection, we tested the hypothesis that the frequency and activity of regulatory T (Treg) cells are influenced by genetic background. Our results demonstrated that the suppressive activity of spleen Treg cells from infected or uninfected BALB/c mice was enhanced, inhibiting IFN-γ and interleukin (IL)-2 production. Infected C57BL/6 mice exhibited a decrease in the frequency of lung Treg cells and an increased ratio CD4(+):CD4(+)Foxp3(+) cells compared with infected BALB/c mice and uninfected C57BL/6 mice. Moreover, infected C57BL/6 mice also had a decrease in the immunosuppressive capacity of spleen Treg cells, higher lung IFN-γ and IL-17 production, and restricted the infection better than BALB/c mice. Adoptive transfer of BALB/c Treg cells into BALB/c mice induced an increase in bacterial colony-forming unit (CFU) counts. Furthermore, BALB/c mice treated with anti-CD25 antibody exhibited lung CFU counts significantly lower than mice treated with irrelevant antibody. Our results show that in BALB/c mice, the Treg cells have a stronger influence than that in C57BL/6 mice. These data suggest that BALB/c and C57BL/6 mice may use some different mechanisms to control M. tuberculosis infection. Therefore, the role of Treg cells should be explored during the development of immune modulators, both from the perspective of the pathogen and the host.