The antibody response to specific immune complexes is under genetic control and correlates with the expression of a recurrent idiotype

Protective antibodies against a sphingomyelinase D from Loxosceles intermedia spider venom elicited in mice with different genetic background

In the present investigation we used a recombinant LiD1 toxin, named rLiD1his, from Loxosceles intermedia brown spider to elicit specific antibodies in mice carrying different Human Leukocyte Antigens class II (HLAII) {DRB1.0401 (DR4), DQB1.0601 (DQ6) and DQB1.0302 (DQ8)} as well as in BALB/C and C57BL/6 control mice. All mice strains produced high antibody titers against rLiD1his but DR4 mice antibodies (the lower responder mice) were not able to recognize L. intermedia crude venom. The anti-rLiD1his sera, except from DR4 mice, were able to neutralize dermonecrotic, hemorrhagic and edematogenic effects of rLiD1his in naïve rabbits. Overlapping peptides from the amino acid sequence of LiD1 toxin were prepared by SPOT method and differences in LiD1 epitope recognition were observed using different mice anti-rLiD1his sera. The region (160)DKVGHDFSGNDDISDVGK(177) was recognized by transgenic DQ8 and DQ6 mice sera. Other epitopes were recognized by at least two different animals' sera including (10)MGHMVNAIGQIDEFVNLG(27), (37)FDDNANPEYTYHGIP(51), (70)GLRSATTPGNSKYQEKLV(87) and (259)AAYKKKFRVATYDDN(273). Among these epitopes, the epitopes 37-51 and 160-177 have already been shown in previously studies as good candidates to be used alone or combined with other peptides to induce protective immune response against Loxosceles venoms. The results presented here highlight the importance of HLAII in antibody response and recognition of specific B-cell epitopes of rLiD1his spider toxin according to HLAII type and impact in the epitopic vaccine development against this spider.

T-cell dependent response to immune complexes abrogates B-cell unresponsiveness to pneumococcal cell wall polysaccharide

Although > 90% of B cells from M167 (mu, kappa) immunoglobulin transgenic (Tg) mice express surface immunoglobulin that binds phosphorylcholine (PC), we found that these mice are unresponsive to immunization with pneumococcal cell wall polysaccharide (PnC), a type II thymus-independent antigen that contains PC. However, when the PnC antigen was presented as a complex with TEPC-15 or McPC-603 antibodies (which are specific for PnC), a vigorous immune response occurred in which the Tg mice produced 10-50-fold more anti-PnC antibody than when immunized with antigen alone. Interestingly, MOPC-167, which expresses the VH and VL regions used to encode the transgene antibody, was found to be a relatively poor 'carrier' for PnC, eliciting a weak anti-PnC antibody response in M167 (mu, kappa) Tg mice. In vivo administration of anti-CD4 antibody dramatically reduced the response to TEPC-15/PnC complexes, suggesting that the response is mediated by immunoglobulin (idiotype)-dependent helper T cells. The results indicate that unresponsiveness to PnC is due not to tolerance of the transgenic B cells but rather to the lack of T-cell help resulting from T-cell tolerance to the transgene-encoded idiotype.

A study of autologous anti-idiotypic antibody-forming cells in mice of different ages and genetic backgrounds

Antibody response to phosphorylcholine, an immunodominant epitope of Streptococcus pneumoniae R36a (Pn), is characterized by a public idiotype, T15, that is expressed on a large proportion of antibody molecules produced by all mouse inbred strains. The ability of the immune system to produce an autologous antibody to T15 upon immunization with Pn vaccine was investigated using a modified ELISA plaque assay for detection of single antibody-forming cells (AFC). The limit of ELISA assay for detection of specific anti-T15 AFC is approximately 300 cells/spleen. However, our studies failed to detect any autologous anti-T15 AFC in the course of the primary antibody response to Pn vaccine in young/adult (2-4 months) BALB/c and C57BL/6 mice. Aged mice (20-22 months) also failed to develop any specific auto-anti-T15 AFC upon the primary Pn immunization, despite the fact that the anti-Pn response in these animals changes both quantitatively and qualitatively. In order to generate specific anti-T15 AFC, BALB/c mice had to be immunized repeatedly with Pn vaccine (four weekly injections) or immunized directly with T15 protein in CFA. Different results were obtained with D1.LP mice that are low responders to Pn and express lower levels of T15 Id as compared to BALB/c. Young D1.LP mice produced high numbers of auto-anti-T15 AFC of both IgM and IgG isotypes following a single immunization with Pn vaccine. The kinetics of auto-anti-T15 response in D1.LP mice was similar to that of the antigen-specific response. These results demonstrate that the ability of the immune network to produce autologous antibody to a shared Id depends on the genetic makeup of the host, and that this response may be regulated by the level of Id expression.

Characterization of the immunodeficiency of RIIIS/J mice: immune response to polysaccharide antigens

RIIIS/J mice lack an autosomal dominant gene(s) that influences the magnitude of the antibody response to several polysaccharide antigens of bacterial origin. Low responsiveness is demonstrable whether polysaccharide is administered as a T-helper-cell-independent or -dependent antigen conjugated to an immunogenic carrier; however, RIIIS/J mice make good anti-hapten antibody responses to haptenated polysaccharides. The low antibody responses of RIIIS/J mice to type III pneumococcal polysaccharide do not appear to be the results of an imbalance in the activity of regulatory T lymphocytes. Compared with other strains of mice, RIIIS/J mice elicit low antibody responses to lipopolysaccharide (LPS). They do not develop a cyclic primary or secondary antibody response to Escherichia coli O113 LPS; the latter is not due to a lack of mitogenic response to E. coli O113 LPS. They also produce auto-anti-idiotypic antibody after being immunized with trinitrophenyl-Ficoll.

Specific antigen/antibody complexes induce the in vivo production of a parallel set of nonantigen-binding idiotype-positive antibodies

Immune complexes prepared with the polysaccharide antigen (PnC) extracted from Streptococcus pneumoniae R36a and two different PnC-specific antibodies were found to differ in their regulatory properties depending on the isotype of the antibody. Thus, complexes formed in antibody excess with TEPC15 (IgA) were suppressive whereas complexes formed with 96-G (IgG3) antibodies enhanced the IgM response to PnC. During the course of these studies, we found that little or no PnC-specific IgG antibody was induced during the response to PnC coupled to sheep red blood cells (PnC-SRBC). Interestingly, however, immunization with 96-G/PnC complexes either alone or with PnC-SRBC resulted in the induction of IgG3 antibodies that express the T15 idiotype (Id) but which do not bind PnC. This unique IgG3 response occurred after injection of 96-G/PnC complexes formed in antibody excess but not when complexes were formed in antigen excess. The Id+ nonspecific IgG3 response peaked on day 5 and could be activated with 96-G/PnC complexes but not with free PnC antigen. The Id+ nonspecific response was not due to polyclonal activation of IgG3 production since there was no difference in IgG3 levels in mice injected with 96-G/PnC complexes with those injected with PnC-SRBC. Finally, mice that had been suppressed for expression of the T15 Id by neonatal injection of anti-Id antibody were able to produce Id+-unspecific IgG3 antibody after immunization with 96-G/PnC complexes, further suggesting that Id+ IgG3 was produced by different clones than those that usually comprise the antibody response to PnC. The results suggest that the formation of IgG immune complexes during an immune response may result in stimulation of idiotypically related clones thus resulting in degeneracy of the immune response.

Production of IL-1-mimicking anti-idiotypic antibodies in rabbits in response to IL-1 immunization

This report describes the characterization of immunoglobulins with interleukin-1 (IL-1)-like activity from the serum of rabbits immunized with partially purified mouse IL-1. Early after immunization, immune sera were found to contain anti-IL-1 antibodies (idiotypes) that inhibited IL-1 bioactivity (augmented-proliferation of PHA-stimulated thymocytes). Later, anti-idiotypic antibodies appeared that mimicked IL-1 activity. These IL-1-like antibodies were affinity purified either on an anti-IL-1-enriched Ig-Sepharose 4B column from an early bleed or sequentially on anti-Ig and Protein A immunoadsorbent columns. By ELISA anti-idiotypic antibodies specifically bound to rabbit anti-IL-1 antibodies. Functionally, IL-1 mimicking antibodies were reproducibly effective in augmenting the in vitro proliferation of PHA-stimulated thymocytes or Con A-stimulated D10 cells. On the other hand, they did not support proliferation of the IL-2-dependent CTLL-2 cells. The ability of IL-1-mimicking antibodies to enhance thymocyte proliferation could be blocked by functional site related anti-IL-1 antibodies. By Western blot, 125I-labeled IL-1 and IL-1-mimicking antibodies bound to a similar 23 Kd mol. wt protein material recovered from the lysate of thymocytes stimulated with PHA for 48 h. That the observed bioactivity could be attributed to antibody molecules and not to contaminant IL-1 was ascertained by several methods, namely (1) SDS-PAGE analysis of 125I-labeled material and (2) resistance to loss of bioactivity by lyophilization. Furthermore, as neither Ig-anti-Ig nor BSA-anti-BSA complexes mimicked IL-1-augmented thymocyte proliferation, a non-specific effect due to immune complexes could be excluded. The occurrence of antibodies mimicking several of the IL-1 functions induced following IL-1 immunization suggests a potential role for the idiotypic network in modulating cytokine activities and a possible link between regulation of the immune system by cytokines and immunoglobulin idiotypes.

Serologic and molecular characterization of the T15 idiotype--II. Structural basis of independent idiotope expression on phosphorylcholine-specific monoclonal antibodies

We examined the expression of T15 idiotopes (Id) on phosphorylcholine (PC)-binding monoclonal immunoglobulins and defined the structural correlates of these Id. The seven monoclonal anti-Id antibodies used as probes recognize distinct determinants that range from the antigen binding site to the CH1 domain on TEPC15. Competition between a series of PC-specific immunoglobulins and radiolabelled TEPC15 for binding to anti-Id in solid phase revealed a broad spectrum of idiotopic crossreactivity. A strong crossreactivity with TEPC15 was observed only in proteins possessing the VK22 light chain. Each of the seven discrete, overlapping T15 Id may be expressed independently of each other on PC-binding immunoglobulins, indicating a significant idiotopic heterogeneity among T15 B-cell clones. No correlation was found between the public (shared) expression of an Id and its position relative to the antigen-binding site. Variations in the primary sequences of PC-binding immunoglobulins were correlated with their effect on individual Id expression. Regions influencing the expression of three Id were localized on a computer display of the three-dimensional structure of the closely related PC-binding myeloma protein McPC603. These data show that some, but not all individual Id determinants may be influenced by amino acid substitutions in the first and third hypervariable loops.

HLA-DR4 and Gm(1,3;5,21) are associated with U1-nRNP antibody positive connective tissue disease

Patients with U1-nRNP antibodies (n = 35, 31 female, four male) were typed for HLA-A, -B, -C, and -DR antigens and IgG heavy chain allotypes G1m(1), -(2), -(3), G3m(5), and -(21). The patient group was clinically heterogeneous. Four met the American Rheumatism Association criteria for systemic lupus erythematosus, six for progressive scleroderma, and 14 for rheumatoid arthritis. Sicca syndrome was present in seven cases. Twenty three had overlapping features compatible with mixed connective tissue disease (MCTD). Healthy blood donors served as controls for HLA typing (n = 64), Gm typing (n = 228), or both (n = 56). Sixty six per cent of the patients with U1-nRNP antibodies were DR4 positive compared with 28% of the controls (relative risk = 4.9, p = 0.00053). The Gm(1,3;5,21) phenotype was found in 46% of the patients and 25% of the controls (relative risk = 2.47, p = 0.0247). Within the patient group Gm(1,3;5,21) was found only in DR4 positive individuals. The coincidence of HLA-DR4 and Gm(1,3;5,21) increases the relative risk values to 8.0 (compared with the group with neither risk factor). DR4 and Gm(1,3;5,21) primarily seem to be related to U1-nRNP antibody formation and not to disease expression. Patients with or without MCTD did not differ with respect to DR4 or Gm(1,3;5,21) frequency. Disease onset was earlier in patients with HLA-DR4/Gm(1,3;5,21) than in patients without both markers (mean 27.9 v 40.1 years; p less than 0.05).

Role of immune complexes in pathogenesis of renal disease

When judged by histological criteria, kidney tissue is practically devoid of immune tissue; as yet a broad spectrum of immunological diseases are targeted at the kidneys, especially at the glomeruli. Glomerular epithelial cells exhibit immune protein receptors and hence could clear immune complexes decorated with complement from the circulation. Alternatively, circulating immune complexes could become trapped in the glomerular filter and start off inflammatory reactions. Anti-glomerular basement membrane antibody reacts with glomeruli and causes glomerulonephritis. The present text is an analysis of the impact of immune complex formation on renal pathology and contains retrospective clinical data of our own hospital obtained on 192 patients undergoing diagnostic renal biopsy.