Role of CD4+ and CD8+ cell subsets during amplification of natural T cell activity against IgG2ab in Igha mice and during induction of IgG2ab allotype suppression in Igha/b mice

Transfer into F1 Igha/b mice of splenocytes from Igha mice sensitized once against B cells from an Ighb congenic strain induces total, chronic, and IgG2ab (IgG2a of the Ighb haplotype)-specific allotype suppression in these recipients. We previously demonstrated that both the CD4+ and CD8+ T subsets were necessary for inducing suppression, but that CD8+, cells by themselves were sufficient for maintaining suppression. We have studied the suppression induction capacity of different mixtures of CD4+ and CD8+ subsets obtained by in vitro cytotoxic treatment of T splenocytes from normal or sensitized Igha mice, and we have established that suppression induction requires the cooperation between CD4+ and CD8+ populations, both of which have to be IgG2ab specific. In addition, Igha mice were sensitized in the absence of CD4+ or CD8+ cells by in vivo cytotoxic treatment performed before and after the sensitization in order to obtain an IgG2ab-specific CD4+ population that has arisen in the absence of CD8+ cells, and vice versa. We found that only IgG2ab-specific CD4+ cells from anti-CD8-treated mice (T'sens CD4+) had the ability to induce suppression in F1 Igha/b hosts. Nevertheless, the real effector cells in this suppression model display the CD8+ phenotype, as in vivo cytotoxic anti-CD8 treatment of Igha/b recipients of T'sens CD4+ abrogates the suppression induction capacity. Taken together, these results show that T'sens CD4+ have an important capacity to recruit CD8+ anti-IgG2ab effector cells from precursors that have been transferred with them into Igha/b hosts. These precursors are actually derived from the T'sens CD4+ cell preparation, because we have recently demonstrated that suppression is maintained by donor T cells throughout the recipient's life. CD4+ cells can have their anti-IgG2ab activity amplified only by means of target cells (i.e., B cells from Ighb congenic mice), whereas, in the absence of CD4+ cells, and despite the presence of target cells, CD8+ cells seem unable to acquire this amplified activity.

Identification of T cell peptides from C gamma 2ab involved in IgG2ab T cell-induced allotypic suppression. Relationship with the MHC haplotype of the suppressor T cell-donor Igha mice

Using the algorithm of the peptidic self-model we selected, from the constant part of the IgG2ab polypeptidic heavy chain, four peptides susceptible to being recognized by the T cells of Igha mice that prevent IgG2ab expression. Among these four peptides, two were capable of enhancing in vivo this T cell activity of Igha mice almost as well as the whole IgG2ab allotype. One of these peptides, C gamma 2ab-248-263, located in the CH3 domain of IgG2ab, was effective in H-2d mice, while the other one, C gamma 2ab-103-118, located in the hinge region of IgG2ab, was efficient in H-2b mice. This demonstrates for the first time that this suppression involves the TCR of the effector cells and peptides derived from the allotype presented in the context of MHC molecules of the target cells, the presentation specificity being dependent on the MHC haplotype. The availability of these peptides will allow us to further understand the role of class I and/or class II MHC molecules in this suppression.

Murine anti-mouse T cell monoclonal antibodies elicit anti-antibodies in mice: intra-species immunization model for estimating potential patient sensitization against humanized anti-T cell antibodies

Humanization of immunosuppressive anti-T cell monoclonal antibodies (mAb) raises the question as to how completely it helps to avoid formation of neutralizing anti-antibodies (anti-Ab) in patients. To get more information on intra-species sensitization against anti-T cell mAb, we produced two immunosuppressive mouse IgG2a anti-mouse Thy-1.2 mAb (MmT1 and MmT5) in AKR/J mice and measured the potential of MmT1 to elicit inhibitory anti-Ab in AKR/J (H-2k), C57BL/6 (H-2b), congenic B10.BR (H-2k) and DBA/2 (H-2d) mice. After one injection once weekly for 4 weeks of 5 micrograms MmT1 (200 micrograms/kg) in C57BL/6 mice, without the use of any adjuvants, high concentrations of anti-Ab directed against MmT1 (300 micrograms/ml) and MmT5 (100 micrograms/ml) were measured by enzyme-linked immunosorbent assay. Similar concentrations of anti-Ab were found in immunized DBA/2 and less in B10.BR mice. No syngeneic anti-Ab could be produced in AKR/J. From the C57BL/6 mice, we raised anti-MmT1+, MmT5- idiotype (IDIO1) and anti-MmT1+, MmT5+ allotype (ALLO1) mAb. An in vivo test system was adapted to measure the inhibitory effects of circulating poly- or monoclonal anti-Ab. It revealed a reduction of in vivo depletion capacity not only of the sensitizing mAb (MmT1), but also of another anti-Thy-1.2 mAb (MmT5), with identical allotype but different idiotype. From this we conclude that intra-species immunization following injection of anti-T cell mAb can produce high titer inhibitory anti-idiotype and anti-allotype antibodies. Implications for hyperchimeric or fully human anti-T cell mAb are discussed.

Endogenous Ig production in mu transgenic mice. II. Anti-Ig reactivity and apparent double allotype expression

In 17.2.25 mu transgenic mice (M54, M95), many of the expressed Ig, whether encoded by the transgene or endogenous H chain genes, react with Ig. IgM antibodies encoded by the 17.2.25 mu transgene transfected into J558L myeloma cells are also Ig reactive. In addition, anti-Ig reactivity was manifested by antibodies of the IgM, IgG, and IgA isotypes from the transgenic mice, suggesting that this characteristic reactivity is associated with VH and VL domains of these antibodies. These antibodies bind the (Fab')2 fragment of mouse IgG1 mAb known to be directed against C mu allotypic determinants. This finding could account for the so called "double producer" B cells found in mu transgenic mice and previously identified in serologic assays conducted with two different anti-mu allotypic reagents. In transgenic mice, a high frequency of the antibodies encoded by the transgene or endogenous H chain genes react with polyclonal and monoclonal antiidiotypic antibodies raised against the 17.2.25 Id. The idiotypic and/or antiidiotypic reactivity displayed by antibodies derived from these transgenic mice is similar to that of antibodies expressed by neonatal B cells of normal mice. Thus, our data suggest that transgene expression can play an important role in shaping the endogenous repertoire of antibody specificities.

HLA antigens and complement C4 allotypes in patients with chronic biologically false positive (CBFP) seroreactions for syphilis: a follow-up study of SLE patients and CBFP reactors

We report a follow-up of our previous study of HLA markers in 118 unrelated patients: 49 with definite systemic lupus erythematosus (SLE) (group 1), 32 with definite or probable SLE and chronic biologically false positive (CBFP) seroreactions for syphilis (group 2), and 37 CBFP reactors (group 3). Definite SLE was confirmed in 28 (90.3%) of the patients in group 2, equally in HLA B8- and HLA B7-positive patients. Three of the CBFP reactors developed SLE, two (40%) out of five HLA B8-positive as compared to one (6.6%) out of 15 HLA B7-positive CBFP reactors (P = 0.07). Fourteen patients died (groups 1 and 2). Eight of the 24 HLA B8-positive patients died in contrast to one of the 20 HLA B7-positive patients (P < 0.02). Of the CBFP reactors, 70.9% had complement C4 null alleles as compared to 47.9% in controls (P = 0.05) and 50% had C4A null alleles as compared to 17.8% in controls (P < 0.05). C4B null alleles were found in 28.6% (28.6% in controls, P is not significant). The null alleles for C4A were not solely in a linkage disequilibrium with the HLA B8 DR3 haplotype. CBFP reactors with C4A null alleles had a higher risk of developing SLE, lupus-like disease or symptoms such as photosensitivity, cutaneous vasculitis and/or autoantibodies than did those with no C4A null alleles (P < 0.02).

Allotypic dependency of the specificity and avidity of human monoclonal IgM rheumatoid factors derived from rheumatoid synovial cells

OBJECTIVE

To better understand the genetic derivation and pathogenicity of rheumatoid factor (RF) molecules in rheumatoid arthritis (RA), we have focused our studies on rheumatoid synovial cells (RSC).

METHODS

Five monoclonal human IgM rheumatoid factor (mRF)-secreting hybridomas were produced from the RSC of an RA patient. Fine subclass specificities and avidities of these RSC mRFs were compared with several paraprotein monoclonal IgM RFs using direct binding (reactivity) and competitive inhibition (specificity and avidity) enzyme-linked immunosorbent assays.

RESULTS

The following observations were made: 1) RSC mRF had greater avidity for IgG than did paraprotein mRF; 2) 4 of the 5 RSC RF were highly avid for IgG3; and, 3) the avidity of RSC RF binding for IgG3 was highest for IgG molecules expressing the G3m(5) allotype.

CONCLUSION

We conclude that RSC RF have different specificities and avidities than do paraprotein RF. This may suggest an antigen-driven process in RA synovium, with the production of higher-avidity IgG3m(5)-specific RSC RF, which could have special pathogenetic importance.

Half-life of the maternal IgG1 allotype in infants

The residence time of maternal IgG1 in the circulation of infants was measured by monitoring f-allotypic IgG1 or f-positive tetanus toxoid antibody in genetically G1mf-negative infants. G1ma-positive maternal tetanus toxoid antibody was similarly monitored in genetically a-negative infants. Blood samples were taken from infants at the age of 1-3 days, ca. 4 months, and ca. 6 months. An exponential decay at the same rate took place from age 1-3 days to 4 months and for the 2 subsequent months. The average concentration of the maternal IgG1 had dropped to ca. 10% of the 1- to 3-day value in 4 months and to ca. 3% in 6 months. The drop was due mainly to clearance but partly also to the weight increase of the child (doubling in 6 months). By correcting for the weight increase, we calculated that ca. 17 and 7% of the original maternal IgG1 was still present at ages 4 and 6 months, respectively. The average half-life of the maternal IgG1 was thus 48.4 days. The concentration of endogenous IgG1 in the cord blood was determined by studying a separate series of mother-newborn pairs. Assuming that cross-reactions of antiallotype reagents had no effect, the highest measured concentration of f-positive IgG1 in infants of f-negative mothers was 10 mg/L, half a percent of adult heterozygote values. Crossreaction may have played a role, however, and the value must be considered the upper limit of the true concentration.

Influence of the Ig H chain locus on autoantibody production in autoimmune mice

Autoimmune disease is influenced by multiple genes. In this study, we investigated the role of one genetic locus, Ig H chain. IgG2a antichromatin, anti-ssDNA, and antihistone autoantibodies (autoAb) from (MRL/Mp-lpr/lpr x C57BL/6-lpr/lpr), (Ighj/b); (C57BL/6-lpr/lpr x C57BL/6-lpr/lpr-Igha), (Ighb/a); and (MRL/Mp-lpr/lpr x MRL/Mp-lpr/lpr-Ighb), (Ighj/b) mice were determined using allotype-specific ELISA. Strikingly, antichromatin and antihistone antibodies (Ab) were comprised of significantly more b allotype than either a or j allotype in all cohorts of F1 mice examined. In mice that produced anti-Sm Ab, the b allotype was used preferentially for these autoAb as well. However, no allotype skewing was observed in IgG2a Ab directed against TNP or DNA, or for total IgG2a. An Igh recombinant locus was utilized to examine the genetic control of b allotype skewing in lpr mice and in chronic graft vs host disease. In both models, the VH region did not appear to be responsible for the preferential use of b allotype. These results indicate a contribution to autoimmunity by the Igh locus and raise the possibility that Ig allotype may influence autoimmune disease by its effect on the production of certain autoAb.

Complement activation by polyclonal immunoglobulin G1 and G2 antibodies against Staphylococcus aureus, Haemophilus influenzae type b, and tetanus toxoid

To obtain information on effector functions of human immunoglobulin G2 (IgG2), we have measured the complement-activating properties of polyclonal IgG subclass antibodies against bacterial antigens. IgG1 and IgG2 were purified from serum samples from five healthy individuals, and complement activation was measured with different bacterial antigens. We used Staphylococcus aureus Wood 46 (STAW), which is a common antigen, Haemophilus influenzae type b (Hib), which is a common pathogenic microorganism in children, and formaldehyde-inactivated tetanus toxin (TT). Bacteria were incubated with antibodies and then incubated with sera from agammaglobulinemic patients as a complement source, and C3c deposition was measured by enzyme-linked immunosorbent assay. We found that anti-STAW IgG2 activated complement to a level similar to that of anti-STAW IgG1. Anti-Hib IgG1 complement activation was as much as seven times higher than that of anti-Hib IgG2 in four individuals. In one individual, anti-Hib IgG2 was more effective in complement activation than anti-Hib IgG1. Anti-TT antibodies showed patterns similar to those of anti-Hib. Our results indicate that IgG2 antibodies may contribute significantly to antibacterial defense. Also, individual differences in antibody effector functions should be taken into account when evaluating the immune status of patients and during early phase 1 studies of new vaccines.

Immunoglobulin allotypes and IgG subclass antibody response to Pseudomonas aeruginosa antigens in chronically infected cystic fibrosis patients

Chronic Pseudomonas aeruginosa lung infection is the leading cause of death in patients with cystic fibrosis (CF). Poor prognosis correlates with a high number of anti-pseudomonas precipitins and with high levels of IgG2 and IgG3 anti-pseudomonas antibodies. Reports of several highly significant associations between certain Gm (genetic markers of IgG on human chromosome 14) and Km (k-type light chain determinants on chromosome 2) phenotypes and immune responsiveness to various antigens suggest that allotype-linked immune response genes do exist in man. Furthermore correlation between Gm types and IgG subclass levels has been reported. A group of 143 CF patients were investigated (31 non-infected and 112 chronic infected). The IgG subclass antibodies to three different P. aeruginosa antigens (P. aeruginosa standard antigen (St-Ag), alginate and LPS) were determined. Immunoglobulin allotypes were determined by haemagglutination inhibition. Samples were typed for G1m(1,2,3, and 17), G2m(23), G3m(5,21), and Km(1,3). Statistical analysis of our data demonstrate that IgG3 anti-pseudomonas antibody levels and Gm markers are related. IgG3 antibody levels to all investigated P. aeruginosa antigens are significantly higher in sera homozygous for Gm(3;5), somewhat lower in heterozygous sera, and significantly lower in sera homozygous for Gm(1,2,17;21). We suggest that genetic differences between the patients may explain the present differences in subclass patterns.

T cell-induced allotypic suppression. Origin of the CD8+ T cells maintaining IgG2ab suppression

One of the problems raised by the T cell-induced allotypic suppression is the origin (donor or host) of the T cells responsible for the chronicity of the suppression. To address this point, we used T cells from Igha/a Thy-1.2 mice whose natural T cell activity against IgG2ab was enhanced in vivo. These T cells were injected into newborn Ighb/b Thy-1.1 mice where they induced complete suppression of IgG2ab expression in around 70% of these recipients. During a study that lasted more than 1 yr, we found that about 3% of the recipient splenocytes were T cells of the donor type. By means of suppression-transfer experiments, using either Thy-1.2+ or Thy-1.1+ cell-depleted splenocytes from mice suppressed in this manner we were able to unambiguously show that Thy-1.2+ cell-depleted splenocytes were incapable of transferring the suppression, whereas Thy-1.1+ cell-depleted splenocytes could. We thus demonstrated that suppression was maintained throughout the recipient's life by donor Thy-1.2+ T cells.

Critical role of HLA-DR beta 1 residue 58 in multiple polymorphic epitopes recognized by xenogeneic and allogeneic antibodies

In a previous study, we identified glutamic acid at position 58 in DR (beta 1*1101) as critical for the epitopes recognized by the DRw11-specific mAb GS88.2, as well as the I-LR1 mAb that recognizes a polymorphic epitope on DR(alpha,beta 1*1101) and some DP molecules. The purpose of this study was to determine whether other polymorphic residues contribute to these epitopes and whether DR beta glutamic acid or alanine 58 and DP beta glutamic acid 56, the analogous position in DP beta, contribute to epitopes recognized by other anti-class-II mAb and allosera. Site-directed mutagenesis and transfection were used to produce cells bearing wild-type or mutant class II molecules that were analyzed with mAbs by flow cytometry and with human allosera by absorption and subsequent microcytotoxicity assays. These studies demonstrate that the residue at DR beta position 58 plays a central role in at least three different mAb epitopes and an epitope recognized by anti-DRw11 allosera. Substitution of glutamic acid for alanine at position 58 of eight DR beta chains caused gain of binding of four mAbs to all of the mutant molecules, except DR(alpha,beta 4*0101). These data suggest that the side chains of DR beta 58 and DP beta 56 point outward from the alpha-helix and directly contact antibody.

Allotype-dependent stimulation of peripheral blood and synovial lymphocytes by IgG3 in rheumatoid arthritis

The immunopathologic process of rheumatoid arthritis (RA) is primarily expressed in the synovium where rheumatoid factor (RF) synthesis is concentrated. We hypothesized that RF synthesized by rheumatoid synovial cells (RSC) may be driven via a T cell-mediated immune response developed against IgG3 epitopes. To identify and characterize specific RSC RF epitopes and T cell antigens, two 28 amino acid peptides homologous with the C-terminus of IgG1 (P1) and IgG3 [G3m(5)] (P3) were synthesized and used in RF-binding studies and lymphocyte proliferation assays. Our results indicate that (i) the C-terminus of the CH3 domain contains epitopes for IgG3-reactive RSC RF; (ii) IgG3-reactive RSC RF binds primarily to IgG3 [G3m(5)]; (iii) P3 stimulated proliferation of T lymphocytes from both RA peripheral blood and RSC; and (iv) RF production was enhanced by P3 in selected RA cell cultures. These observations suggest that the C-terminus of IgG3 allotype G3m(5) may be important in T cell activation and RF production in RA.

Alloimmune thrombocytopenia may be associated with systemic disease

Adverse outcome was encountered in a case of neonatal alloimmune thrombocytopenia after in utero platelet transfusion. This may have resulted from generalized systemic vascular endothelial damage, because several cell types, including umbilical endothelial cells, have been shown to contain surface molecules similar to the receptor containing the PlA1 antigen.

Autoimmunity in vitiligo: relationship with HLA, Gm and Km polymorphisms

Eighty-six patients affected by vitiligo were investigated for Gm, and Km polymorphisms, HLA markers and the presence of organ and non organ-specific autoantibodies. Vitiligo patients had an increased frequency of autoantibodies (71%), in particular anti-parietal cells (26.6%), antithyroglobulin (24.4%) and antithyroid microsomal antibodies (43%). One patient was also affected by Hashimoto's thyroiditis, 4 by Graves' disease and two others by nontoxic, multinodular goiter. No correlation was found between chronologic age and sex and the presence of autoantibodies, while an increased frequency of organ-specific autoantibodies was found with longer duration of vitiligo. HLA-A3 and Gm (3; 23; 5, 10, 11, 13, 14) phenotype frequencies were significantly increased in patients without autoantibodies (P less than 0.05). Patients negative for these two phenotypes were significantly more prone to develop autoantibodies than those positive (P = 0.0032). C4AQO allele showed a significantly decreased frequency in the whole group of patients when compared to the controls (P less than 0.05).

Gm and Km allotypes in autoimmune diseases

The associations or linkages between the polymorphisms of the Gm and Km immunoglobulin allotypes and the susceptibility to autoimmune diseases, including diseases with immuno-pathological pathogenesis are reported in this review. These diseases include multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, insulin-dependent diabetes mellitus, Crohn's disease, coeliac disease, Graves' disease, atrophic thyroiditis, Hashimoto's thyroiditis, myasthenia gravis, chronic active hepatitis, alopecia areata, uveitis, vitiligo, Turner's syndrome, glomerular nephritis, Berger's disease and idiopathic dilated cardiomyopathy. Immunoglobulin allotypes are described as well as the statistical methods used to analyse the data.

Comparison of IgD+ and IgD- thoracic duct B lymphocytes as germinal center precursor cells in the rat

Genetically marked thoracic duct B cell subpopulations rich in either IgD+ or IgD- B cells were transferred to non-irradiated, congenic rats in order to compare the capacities of IgD+ versus IgD- B cells to form germinal centers (GCs). This comparison was made quantitatively based on flow cytometric analyses of lymph node cells prepared from chimeric rats 7 days after s.c. immunization. Donor-origin and host-origin B cells were distinguished using anti-Igk antibodies, and GC B cells were distinguished from other B cells in suspension by their lack of labeling with the mAb HIS22. IgK+ HIS22- lymph node cells corresponded well to GC B cells: they contained many large cells, were IgM+ but mostly IgD-, expressed relatively lower levels of IgM than HIS22+ B cells, and increased in number and frequency in response to antigen. Results from flow cytometric analyses, corroborated by immunofluorescence histochemical studies, showed that cell-for-cell, IgD- B cells from GCs much more efficiently than IgD+ cells. B cell populations enriched for IgD- cells became relatively more distributed to GCs than to other lymph node B cell areas and gave rise to many more GC B cells of donor origin per transferred B cell than whole, unseparated thoracic duct B cells (for which greater than 97% were IgD+). IgD- B cells from rats primed deliberately with antigen also became relatively more distributed to GCs and gave rise to more GC B cells of donor origin than either IgD+ B cells from primed donors or IgD- B cells from unprimed donors.(ABSTRACT TRUNCATED AT 250 WORDS)

Peritoneal B cells regulate the numbers of allotype-matched pre-B and B cells in bone marrow

The mechanisms regulating growth and differentiation of B-cell precursors in adult bone marrow (BM) and/or selecting immunocompetent cells for peripheral export are poorly understood. We report here that small numbers of activated peritoneal B cells selectively suppress the numbers of small pre-B (B220+IgM-) and B (B220+IgM+) cells in BM, if transferred into syngeneic adult mice. No significant alterations are detected in other BM cell lineages or in peripheral lymphocytes of recipient mice. Both CD5+ and CD5- peritoneal B cells display this activity, but the same or higher numbers of similarly activated splenic B cells have no effect. Suppression of B-lineage cells is independent of T lymphocytes but requires that both donor and recipient are matched for immunoglobulin allotypes. These findings provide evidence for regulation of BM B-cell production by peripheral B cells, especially when located in the peritoneal cavity, and ascribe regulatory roles to the peritoneal B-cell compartment. They also could contribute to understanding the control of total B-lymphocyte numbers in the organism.

Immunoglobulin allotypes are not associated with HLA-antigens, autoantibodies and clinical symptoms in systemic lupus erythematosus. Members of the SLE Study Group

Immunoglobulin heavy chain (G1m, G2m, G3m, A2m) and kappa light chain (Km) allotype and phenotype frequencies of 323 central European Caucasian patients with systemic lupus erythematosus (SLE) were examined and correlated with various genetic, serologic and clinical markers of SLE. No significant associations were found between immunoglobulin allotypes or phenotypes and all 20 parameters tested (nephritis, vasculitis, arthralgias, photosensitivity, discoid lesions, central nervous system disease, Raynaud's phenomenon, sex, anti-Ro, anti-La, anti-nRNP, HLA-DR1-DR7, HLA phenotypes B8-DR3, B7-DR2). It could therefore be assumed that Gm, A2m and Km allotypes were not associated with HLA-antigens and had no influence on the serologic and clinical expression of SLE.

Prenatal diagnosis of neonatal alloimmune thrombocytopenia using allele-specific oligonucleotide probes

The prediction of neonatal alloimmune thrombocytopenia (NATP) in affected families has, in the past, been based on information about gene frequencies of the antigen systems involved, parental phenotyping, and fetal platelet counts. We explored the feasibility of allele-specific oligonucleotide probe typing for PIA antigens to determine the risk of second or subsequent fetuses in families where one infant had a diagnosis of anti-PIA1-mediated NATP. A total of eight families at risk for delivering an affected fetus were studied with both serologic and oligonucleotide typing. The correlation between serologic and oligonucleotide PIA types was 100%. Similarly, in an additional eight families not at risk for PIA1-mediated NATP, serologic and oligonucleotide typing maintained a perfect correlation. DNA isolated from fetal leukocytes as well as fetal amniocytes was successfully typed using this technology. Oligonucleotide-based typing of fetuses at risk for NATP whose fathers are heterozygous for the PIA antigens allows early recognition of affected fetuses so that prenatal therapy of mothers can be instituted if necessary. When fetuses are found to be unaffected, invasive, and/or expensive, prenatal interventions can be avoided.

Is there really a "lack of natural tolerance to allotypic gamma-globulins in rabbits"?

We present data of extended studies on the possibility of maternally derived allotype Ig inducing a state of natural immunological tolerance to a non-inherited allotype in the offspring. Rabbits homozygous at the a locus, encoding allotypes in the variable region of immunoglobulin heavy chains, and rabbits homozygous at the unliked b locus, encoding allotypes of the constant region of kappa 1 chains, were immunized at the age of 2 months against the non-inherited allotype of their heterozygous mothers to which they had been exposed in utero and in early life. As control, we immunized rabbits of the same Ig phenotype but born to homozygous mothers, and therefore not exposed to that allotype. Immunization was done in a3/a3 offspring of either a1/a3 or a3/a3 mothers, by injecting a 1 IgG, and in b6/b6 offspring of b4/b6 or b6/b6 mothers, by injecting b4 IgG. The IgG was injected either in a soluble form or emulsified in adjuvant. Injection of soluble IgG elicited only a low response, if any, revealing no differences between the various groups. All rabbits responded upon immunization with IgG in adjuvant. We have not found any good evidence for natural tolerance to a non-inherited allotype, although progeny of a1/a3 mothers had slightly decreased responses to a1. On the contrary, progeny of b4/b6 mothers responded even better than offspring of b6/b6 mothers, upon such immunization with b4. To induce tolerance experimentally, we injected newborn rabbits, either from heterozygous a1/a3 or from homozygous a3/a3 mothers, with a1 serum or IgG. Newborn of heterozygous b4/b6 or of homozygous b6/b6 mothers were injected with b4 serum or IgG in the same way. Such treatment resulted in partial tolerance to each allotype. In an attempt to amplify the tolerizing effect of the maternal a1 Ig, we injected newborn rabbits of a1/a3 mothers with the serum of their mother. The response upon subsequent immunization with a1 allotype of another individual did not differ significantly from the response of control rabbits. The response was much poorer when rabbits were injected with nonmaternal tolerogen at birth, and when the same Ig preparation was used as immunogen. In a control experiment, neonatal injection of xenogeneic proteins, human IgG or bovine serum albumin, clearly resulted in tolerance. We speculate that tolerance to allotypes is established in the T cell repertoire only but bypassed by recognition of idiotypic determinants on antigen molecules by helper T cells, which trigger anti-allotype antibody formation by allotype-specific B cells. The end result of it is a lack of natural tolerance.

Igh-1b-specific CD4+CD8- T cell clones of the Th1 subset selectively suppress the Igh-1b allotype in vivo

The demonstration of major histocompatibility complex (MHC)-restricted T helper (Th) cells specific for peptides from the variable (V) regions of syngeneic immunoglobulin (Ig) (idiopeptides) opens the possibility that Th cells regulate B cell functions via idiopeptide-based cognate T-B interactions. As a model for such interactions we investigated the influence of Ig allotype-specific T cells on the differentiation of H-2-syngeneic B cells expressing that particular Ig allotype. We established a BALB/c (H-2d, Iga) CD4+CD8- T cell line and clones of the Th1 subset (interleukin 2+, interleukin 4-, interferon-gamma+, tumor necrosis factor-alpha+) that recognized Igh-1 (IgG2a) of the b allotype (Igh-1b) together with I-Ad. These T cells specifically suppressed surface Igh-1b+ B cells in vitro and in vivo. In 12 out of 15 6-week-old (BALB/c X B10.D2)F1 mice neonatally injected with Igh-1b-specific T cells, the serum Igh-1b concentrations were less than 5% of the levels in the controls. Thus, allotype suppression can be accomplished solely by adoptive transfer of Igh-1b-specific CD4+ T cells. The in vivo suppression was specific for Igh-1b+ B cells as the recipients' levels of Igh-1a and Igh-4b (IgG1b) were unaffected. The V beta 14-specific anti-T cell receptor (TcR) monoclonal antibody 14-2 inhibited activation of hybridomas derived from two of the clones. Collectively the data indicate that suppression resulted from cognate interactions between allopeptide-specific TcR alpha/beta+ T cells and normal unmanipulated B lymphocytes presenting their endogenous Igh-1b in association with MHC class II molecules. The data support the possibility that normal B cells can be suppressed by idiopeptide-specific T cells in vivo.

Gm allotypes influence the production of IgG3 but the effect is age-dependent

Serum concentrations of IgG3 were found to be higher in Gm-f-positive (= b-positive) than in f-negative individuals except in young children. Young children aged 3-4 months had a mean concentration of 0.24 g/l of IgG3 regardless of allotype. The concentration gradually rose with age in f-positive individuals to a geometric mean of 0.56 g/l in adults but it remained essentially unchanged in f-negative people. A corresponding allotype effect was seen in influenza-specific antibody responses. While the total IgG response (mainly IgG1) was equally strong in f-positive and in f-negative patients, f-positive (= b-positive) patients produced more IgG3 antibodies than f-negative patients. The difference between geometric mean values of opposite homozygotes (f/f versus f-negative) was 2.3-fold (p = 0.0113). This finding indicates that the b-positive gamma-3 allele is more productive than the g-positive allele.