Molecular analysis of a germ line-encoded idiotypic marker of pathogenic human lupus autoantibodies

Id-16/6 is an idiotypic marker found in both IgM and IgG antibodies, as well as in the tissue lesions of patients with SLE. The prototypic Id-16/6+ mAb is 18/2, whose VH3-derived H chain is encoded by an unmutated germ-line gene. We found that the H chains of VH3-derived Id-16/6+ antibodies contain the major determinants of Id-16/6. Moreover, B cell clones from which those antibodies were harvested produce RNA that hybridized under conditions of high stringency to oligonucleotide probes corresponding to the CDR of the VH segment of 18/2. Western blots of Id-16/6+ mAbs with anti-Id confirmed the association of the Id with H chains. Id-16/6 can identify a subgroup of VH3-derived antibodies we have termed the 18/2 CDR family. However, Id-16/6 can also be expressed in some antibodies unrelated to the 18/2 CDR family. No characteristic Ag-binding specificity was found among the members of the 18/2 CDR family. The principal phenotypic feature shared by all known members of the family is Id-16/6.     

Comparative biochemical and genetic characterization of clonally related human B-cell lines secreting pathogenic anti-Pr2 cold agglutinins

To study the biology of cold autoimmune hemolytic anemia, Epstein-Barr virus (EBV)-transformed B-cell clones were established from a patient with splenic lymphoma associated with immune hemolysis due to an anti-Pr2 cold autoantibody. Studies were performed comparing the cold autoantibody present in culture supernatants of these cell lines to the pathogenic cold autoantibodies present in the patient's plasma. Cytogenetic studies of splenic lymphocytes demonstrated an abnormal karyotype (51XX, +3, +9, +12, +13, +18). After EBV transformation, eight clones secreting IgM, kappa anti-Pr were isolated; each clone had the same abnormal karyotype as above. DNA isolated from the clones and spleen was analyzed by Southern blot hybridization with JH, C mu, and C kappa probes; identical gene rearrangements were seen in each case. Anti-Pr antibodies, isolated from culture supernatant and serum were compared by isoelectric focusing (IEF) and demonstrated similar banding patterns. Distinctive binding patterns, however, were observed in 2/8 clones, suggesting structural differences. Adsorption studies with red blood cells further showed that the observed IEF banding patterns were solely due to anti-Pr cold autoantibody. With a thin-layer chromatography method, the biochemical determinants recognized by the cold autoantibodies were defined as glycolipids containing Neu Ac alpha 2-3Gal beta 1-4Glc sequences. The data demonstrate that the autoantibodies of the EBV-transformed B-cell lines were similar to the pathogenic monoclonal serum autoantibody in both structure and specificity. These clonal cell lines may thus serve to further study the biology of human B-cell lymphomas with defined autoantibody specificity.     

Molecular analysis of heavy and light chains used by primary and secondary anti-(T,G)-A--L antibodies produced by normal and xid mice

The primary (1 degree) antibody response to (T,G)-A--L shows limited heterogeneity, consisting mostly of side chain-specific antibodies that bind GT and that express the TGB5 idiotype (Id). The secondary (2 degrees) response is very diverse: antibodies that bind the backbone A--L constitute a third of the response, and a high proportion of the side chain-specific antibodies do not bind GT and are TGB5 Id-. To provide a molecular basis for understanding this difference in repertoire expression, we analyzed the Ig genes used by heavy and light chains of 1 degree and 2 degrees side chain-specific anti-(T,G)-A--L hybridoma antibodies (HP). Southern blot restriction analysis and nucleotide sequence analysis of the expressed genes used by three TGB5 Id+ 2 degrees HP showed usage of three different VH genes in two VH gene families (36-60 and J558), different D segments, and two different Vk1 genes (the Vk1A and Vk1C subgroups). Thus, antibody heterogeneity in the 2 degrees response is contributed by combinatorial diversity of distinct germ-line genes. Nucleotide sequence analysis of the expressed genes used by TGB5 Id+ 1 degree HP showed use of highly homologous VH genes in the J558 VH gene family and highly homologous Vk1A genes. The majority of TGB5 Id+ 1 degree HP from different donors gave similar heavy and similar light chain gene rearrangements by Southern blot restriction analysis, after correction for known or potential J region differences. The combined nucleotide sequence and Southern blot restriction analysis data suggest that most 1 degree B cells use the same or very similar VH and Vk genes, i.e., the 1 degree response is paucigenic. Different D segments were used by the TGB5 Id+ 1 degree and 2 degrees HP that were sequenced, and there was no apparent correlation between TGB5 idiotypy and VH, D gene, or JH gene usage. However, all TGB5 Id+ HP sequenced used highly homologous genes from the Vk1 group. Expression of a Vk1 light chain correlates with, but is not sufficient for, TGB5 idiotypy, because one GT-binding, TGB5 Id- HP was found to use a Vk1C subgroup light chain. By Southern blot and nucleotide sequence analysis, the Vk genes used by two TGB5 Id+ 2 degrees HP from xid mice are highly homologous, if not identical to the Vk1A gene(s) used by 1 degree and 2 degrees Id+ HP from wild-type mice.     

Recognition of a B cell lymphoma by anti-idiotypic T cells

Idiotypic IgM derived from a B cell lymphoma can act as a tumor-associated Ag, in that immunization with this purified protein generates an anti-idiotypic immune response that specifically suppresses tumor development. Spleens of immune mice contain T cells that proliferate in response to idiotypic IgM. However, idiotypic Ag is presented to the T cells most efficiently in its natural form at the surface of the lymphoma cells, than as soluble IgM plus presenting cells. Variant tumors that display either little or no idiotypic IgM at the cell surface, but which are otherwise indistinguishable from parental tumor, induce a weak response or fail to stimulate the T cells, respectively. Anti-idiotypic lines and clones have been derived from the splenic T cells by growth in the presence of irradiated tumor cells. Phenotypic analysis revealed that cells from both lines and clones express CD3 and CD4 Ag, but not CD8. Recognition of tumor Id, which required no added presenting cells, was inhibited by antibody against MHC class II Ag, and variably by anti-CD4. Proliferative responses were inhibited by anti-idiotypic antibodies, but also by antibodies against the constant region of the mu H chain, indicating that perturbation of the surface IgM abrogates availability of idiotypic determinants to the T cells.     

"Nonspecific" immunoenhancing T cells in tumor-bearing mice include anti-idiotypic subsets

Splenocytes from DBA/2 mice inoculated 3 wk earlier with syngeneic P815 mastocytoma tumor cells produce increased numbers of antibody plaque-forming cells (PFC) when stimulated with either sheep red blood cells (SRBC) or phosphorylcholine (PC) on Streptococcus pneumoniae R36a in vitro. The nature of this nonspecific hyperreactivity was investigated in mixed cultures of purified splenic T and B cells. The addition of T cells from P815 tumor-bearing mice (TP815) into the cultures of normal B cells produced a significant enhancement of the PFC response to both SRBC and PC, when compared with the effect of normal T cells added to control cultures. The idiotypic profile of the enhanced anti-PC response was studied by a PFC-inhibition assay with monoclonal antibodies against two distinct idiotopic determinants (Id) of the T15 family. Normal B cells produced greater than 90% of T15 Id-positive (Id+) PFC. Addition of normal T cells diminished the proportion of T15 Id+ PFC to approximately 60%, whereas the rest of PFC were Id-. Addition of the immunoenhancing TP815 cells into the normal B cells cultures elevated the number of both T15 Id+ and Id- PFC responses, proportionally. However, when TP815 cells were first incubated on T15 protein-coated dishes and the non-adherent fraction was added to B cell cultures, the anti-PC PFC response remained enhanced but consisted of predominently T15 Id- PFC. These observations suggest that the early stage of P815 tumor growth activates various populations of specific helper/amplifier T cells including subsets with anti-idiotypic activity and that the generalized increase of antibody response to various antigens in tumor-bearing mice may be regarded as a polyclonal activation of specific T cells.     

Generation of somatic variants of a B cell hybrid mediated by a non-cytolytic L3T4+ idiotype-specific T cell

We previously reported that idiotype (Id)-loss, stable somatic variants of a B cell hybrid, 2C3E1, are generated both in vitro and in vivo, after interaction of the Id-positive tumor cells with autologous Id-specific effector T cells. The present investigation was undertaken to elucidate further the nature and functional characteristics of the effector T cells. We report here that the idiotype-specific cells mediating the generation of Id- tumor variants are Thy1+ L3T4+ Lyt-2- cells, which respond to specific idiotypic stimulation by secreting IL-2 in vitro. No IL-2 is secreted in response to unrelated Ig or an Id/Ig-2C3E1 tumor variant. Furthermore, the Id-specific T cells exert strong suppressive effects on the expression of 2C3E1 Ig and the effects can be reversed by blocking the L3T4+ T cells with monoclonal anti-L3T4 antibody in vitro during the initial 3 days of co-culture. After 4 days, the T cell-mediated suppression of the 2C3E1-Id is irreversible. In addition to the in vitro studies we have determined that the administration of anti-L3T4 mAb to mice just before priming with idiotype-bearing tumor cells also abrogates the suppressive effects of the idiotype primed spleen cells on Ig expression of 2C3E1. To study the Id-specific effector T cells in more detail we have generated functional Id-specific L3T4+ T cell lines. These T cell lines have been shown to recapitulate the generation of Id- tumor variants that we observed with Id-primed spleen cells. It is concluded that L3T4+, Id-specific Ts cells are responsible for the generation of somatic variants of the B cell hybrid 2C3E1 and that the induction or selection of these variants progresses from a reversible phase to an irreversible phase.     

A molecular and structural analysis of the VH and VK regions of monoclonal antibodies bearing the A48 regulatory idiotype

The results presented in this paper explore the molecular basis for expression of the A48 regulatory Id (RI). A48 RI+ mAb derived from idiotypically manipulated mice molecularly resembled the A48 and UPC 10 prototypes of this system by utilizing a VHX24-Vk10 combination. Id expression by these antibodies was not restricted by a particular D region sequence, JH, or JK segment, but quantitative differences in Id expression were associated with utilization of different members of the VK10 germ-line gene families. The VL sequences of these A48 RI+ mAb has identified amino acid residues lying in four different idiotope-determining regions which may contribute to the structural correlate of this Id. A comparative sequence analysis of the VH regions of these VHX24 utilizing A48 RI+ mAb with several A48 RI+ mAb utilizing VHJ558 or VH7183 VH genes as well as a hybrid transfectoma antibody derived from two A48 RI-, VHJ558 utilizing hybridomas, all suggested that four nonconsecutive positions which lie outside the idiotope-determining regions may contribute structural elements toward expression of this Id. The VH and VL regions of the A48RI+, VHX24-Vk 10+ mAb showed low to moderate levels of somatic mutation which showed different patterns of distribution between the complementary determining region (CDR) and framework regions in the H and L chains. Although the VK sequences contained 50% of the replacement mutations in the CDR, with a replacement/silent mutation ratio of 10, the CDR of the VH sequences contained only 31% of the replacement mutations with a replacement/silent mutation ratio of 0.69.     

Evidence for idiotypic- and antiidiotypic B-B cellular interaction with the use of cloned antiidiotypic B cell line

Immunization of BALB/c mice with MOPC104E myeloma protein induces antiidiotypic B lymphocytes that have Id-specific enhancing activity on antibody production. The B-B cell interaction was restricted to both Igh and class II MHC. However, anti-Thy-1 and C-treated splenic B cells were maintained for more than 1 y in a mixture of Con A-stimulated splenocyte culture supernatant and synthetic medium. In applying the long term culture method, we have established a cloned B cell line named B19-1d, B19-1d cells are specific to MOPC104E or J558 cross-reactive Id and they express surface mu, lambda but no Ly-1. B19-1d do not spontaneously secrete Ig but produce them upon stimulation with bacterial LPS. The effect of B19-1d cell line on idiotypic antibody production was tested. Addition of only 10 to 100 B19-1d cells into dextran-immune B cell culture greatly enhanced the Id+ antidextran antibody responses. On the contrary, the antidextran antibody production was suppressed by the higher doses of B19-1d cells. The effective cooperation between dextran-immune B cells and B19-1d cloned B cells was restricted to class II MHC. The role of idiotypic- and antiidiotypic B-B cell interaction in immune regulation and repertoire generation was suggested.     

Allogeneic manipulation of the GAT idiotypic cascade. Immunization of C57BL/6 mice by BALB/c anti-idiotypes stimulates similar strain-specific V genes as the original antigen

Antibodies specific for the immunizing Ag (Ab1) (Id+ Ag+) and Ab3 (Id+ Ag+ or Id+ Ag-) of the (Glu60 Tyr10 Ala30) (GAT) idiotypic cascade express similar pGAT public determinants in BALB/c and C57BL/6 strains. These determinants have been shown to be dependent upon both VH and Vkappa encoded segments. The VH of the BALB/c Ab1 (germ-line gene H10) and that of the C57BL/6 Ab1 (germ-line gene V186-2) are only 75% homologous, whereas VK are much more conserved. C57BL/6 mice were immunized with BALB/c Ab2 (anti-idiotypic) antibodies and monoclonal Ab3 were derived after fusion of immunized spleen cells with the nonsecreting hybridoma cell line Sp/2.0-Ag. From 13 cell lines, five clones (four Id+ Ag- and one Id+ Ag+) were isolated and the mRNA V regions sequenced. Immunization with BALB/c anti-idiotypes elicits expression of the same or closely related C57BL/6 VH and Vkappa genes as when C57BL/6 mice were immunized with GAT, although functional VH BALB/c equivalents have been isolated in the B6 strain. Our results suggest that manipulation of the repertoire via antigenic or idiotypic stimulation both lead to the expression of different genes in different strains. They further confirm that the immune system is largely degenerate, for both idiotype expression and Ag recognition.     

Mouse monoclonal antibodies to chicken VH idiotypic determinants reactivity with B and T cells

We have prepared mouse monoclonal antibodies against idiotypic (Id) determinants on chicken antibodies to N-acetylglucosamine (NAGA) and p-aminobenzoic acid (PABA) made by inbred line EL 6(3) birds. The monoclonal anti-NAGA Id antibody, termed CId-1, reacted with affinity purified antibodies to NAGA, but not with antibodies specific for PABA, arsanilic acid (Ars), phosphorylcholine (PC), or with normal chicken IgG and IgM. The monoclonal anti-PABA ID antibody, termed CId-2, reacted with anti-PABA antibodies and to a lesser extent with anti-Ars antibodies, but not with anti-NAGA, anti-PC, and normal IgG and IgM. The Id determinants were found among antibodies to NAGA and PABA made by outbred and inbred lines of White Leghorn chickens. The binding of the CId-1 and CId-2 antibodies to intact homologous anti-NAGA and anti-PABA antibodies, respectively, was not hapten-inhibitable in either case. Both anti-Id antibodies reacted specifically with isolated homologous heavy chains, suggesting VH Id specificities. The monoclonal CId-1 and CId-2 antibodies were reactive by immunofluorescence with approximately 0.9 and 0.2%, respectively, of the circulating lymphocytes and with approximately 0.4 and 0.15 of plasma cells. CId-1+ and CId-2+ bursal cells were first detected on the 16th and 14th days of incubation, respectively; both reached maximal frequencies by the 17th day of incubation. The CId-2 antibody reacted exclusively with immunoglobulin-positive cells. The CId-1 antibody also reacted with a subpopulation (0.4%) of immunoglobulin-negative lymphocytes from normal and agammaglobulinemic chickens, and thus would appear to recognize an idiotypic determinant expressed by certain clones of B and T cells.     

The targeting of CD4+ T lymphocytes to a B cell lymphoma. A comparison of anti-CD3-anti-idiotype antibody conjugates and antigen-anti-idiotype antibody conjugates

We have targeted CD4+ cytotoxic Th (Th/c) lymphocytes to a B cell lymphoma, through the use of a bispecific antibody containing binding sites for both the CD3 complex on the Th/c and the Id on the surface Ig of the B lymphoma (anti-CD3-anti-Id). Cloned, keyhole limpet hemocyanin (KLH)-specific Th/c cells were nonspecifically activated by the anti-CD3-anti-Id conjugate to lyse the Id+ B lymphoma A20-HL. This cytotoxicity was not inhibited by antibodies to CD4 or LFA-1 alpha molecules. The anti-CD3-anti-Id conjugates also induced non-lytic Th clones to become cytotoxic, a function not elicited when these cells were activated specifically by Ag. We compare this model to our previously described system where we targeted the KLH-specific Th/c cells to the Id+ B lymphoma A20-HL via a conjugate consisting of KLH covalently linked to the anti-Id antibody (KLH-anti-Id). The mechanism involved processing and presentation of KLH by the A20-HL target. This Ag-specific cytotoxicity was MHC class II restricted and was inhibited by antibodies to the CD4 molecule. In both systems, activation of the Th/c cells resulted in bystander killing of tumor but not normal targets. These results may have important implications for the use of Th/c cells in tumor immunotherapy.     

Regulation of the anti-alpha(1----3) dextran IgG antibody response of BALB/c mice by idiotype-specific T suppressor lymphocytes.

The immune response of BALB/c mice against the so-called thymus-independent bacterial Ag alpha(1----3) dextran (Dex) is restricted to the expression of few major idiotypes (Id). It is furthermore under the control of T lymphocytes which regulate the isotype expression in such a way that they prevent anti-Dex IgG antibody production upon immunization. At the same time these T cells are part of a regulatory system for Dex-specific B cell memory formation. The underlying Ts cell activity has previously been analyzed by using euthymic and athymic congenic animals. Now we have isolated CD4-positive Id-specific T cell lines and clones which by several criteria are representatives of the above Ts cells. They inhibit in vitro proliferation and antibody secretion of Dex-specific hybridoma B cells. They prevent Id-restricted in vivo IgG anti-Dex antibody formation in T cell-reconstituted BALB/c nu/nu mice. At the same time they enforce, again Id-specific, accumulation of Dex-specific B memory cells. As has been shown previously under the influence of splenic Ts cells, these B memory cells are arrested in the original host but can be expanded and activated for anti-Dex IgG antibody formation upon adoptive transfer into X-irradiated allotype congenic nonresponder BALB.Ighb mice. The data show that the regulatory influence of T cells on the anti-Dex response is Id specific. It can now be studied by means of cloned Ts cells.     

Germline V genes encode viable motheaten mouse autoantibodies against thymocytes and red blood cells

Autoantibodies against thymocytes and RBC may contribute to the pathophysiology of homozygous viable motheaten (mev) autoimmune disease. Whether the production of these autoantibodies in mev mouse results from polyclonal nonspecific B cell activation or specific Ag-driven stimulation is not known. To understand the mechanisms involved in the induction of antithymocyte autoantibody response in mev mouse, we have studied the fine antigenic specificity, structure, and origin of three antithymocyte autoantibodies derived from mev splenic B cell hybridomas. Western blot analysis showed that these mAb bind to polypeptides of 33 and 105 kDa present in RBC and thymocytes, respectively. Additional specificities for the epitopes present in other polypeptides distinguished these three autoantibodies. Northern hybridization and flow microfluorimetry analysis indicated that these hybridomas are derived from the Ly1+ B cell subset. These autoreactive Ly-1 B cell hybridomas, chosen on the basis of their specificity, expressed L chain V genes from a single VK family (VK9) and VH genes from J606 and S107 families. Hybridomas UN34.11 and UN42.5 expressed the VK9 gene identical to that used by peritoneal Ly1+ B cells from various mouse strains and malignant B lymphoma cells secreting anti-mouse RBC treated with proteolytic enzyme bromelin and anti-SRBC antibodies. The third hybridoma, S2-14.2, used a VK9 gene identical to that expressed by MOPC41. None of the VK genes encoding these autoantibodies showed any somatic mutations. In the case of VH genes, the two hybridomas UN42.5 and S2-14.2 derived from two separate fusions, used identical VH genes from the J606 family. The third hybridoma UN34.11 used unmutated V11 germline VH gene, a member of the S107 family. Southern hybridizations, using oligonucleotide probes specific for CDR1 and CDR2, showed that the VH genes encoding the J606 autoantibodies were derived from a germline gene found in the 6.7-kb fragment of EcoRI-digested germline DNA. This germline VH gene is distinct from VH22.1 germline gene that codes for antigalactan antibodies. Sequence analysis of this gene showed perfect homology with the rearranged VH genes confirming the lack of somatic mutations. Thus, our data demonstrate that antithymocyte antibody response occurring in mev mouse is polyclonal and it involves Ly-1 B cells expressing unmutated germline VH and VK genes. These results indicate that antigen driven stimulation may not play an important role in the induction of anti-thymocyte antibody response in mev mouse.     

IgM induction in murine B hybridomas with Ia-restricted T cell clones: a monoclonal model for T and B cell interactions in antibody response

The mechanism of MHC-restricted T and B cell interactions in antibody response was studied with IgM-inducible B hybridomas and antigen-specific helper T cell clones. B hybridomas were prepared by fusion between splenic B cells from (CBA/N (H-2k) X BALB/c (H-2d)) F1 (NBF1) male mice and a B lymphoma cell line, M12.4.5. A B hybridoma clone, 1M70, which expressed I-Ad but not I-Ak determinants was chosen in the present study. IgM secretion was induced in 1M70 when it was cocultured with a "resting" KLH-specific and H-2d restricted helper T cell clone in the presence of KLH. A "resting" KLH-specific and H-2k restricted T cell clone did not induce IgM secretion in 1M70 even in the presence of KLH. However, when these KLH-specific T cell clones were activated by KLH and appropriate antigen presenting cells, both H-2d and H-2k restricted T cell clones induced IgM secretion in 1M70 even in the absence of KLH. A monoclonal anti-I-Ad antibody inhibited IgM secretion induced by a "resting" H-2d restricted T cell clone, but not by an "activated" T cell clone. These results indicated that T cell clones recognized antigens in the context of Ia molecules on B hybridomas in a MHC-restricted manner and were activated to produce B cell stimulatory factors which in turn acted on B hybridomas in a non-MHC-restricted manner and induced differentiation of B hybridomas into IgM secreting cells.     

Detection of a regulatory idiotype on a spontaneous neonatal self-reactive hybridoma antibody

To investigate the physiologic relevance of an idiotype-driven regulation of the immune system, we began a search for spontaneous self-reactive hybridomas in neonatal BALB/c mice. We sought hybridoma antibodies reactive with thyroglobulin (Tg) and expressing Id62, a recurrent idiotype with regulatory properties borne on induced adult autoantibodies to Tg. We describe herein such a neonatal Tg binding/Id62-positive monoclonal antibody (mAb) B10H2, and compare it with prototype mAb 62, an adult Tg-binding/Id62-positive mAb. Both mAb react with the same Tg epitope, as demonstrated by their abilities to totally inhibit the binding of the other to Tg. Moreover, as assessed by a double-reciprocal plot of their binding to Tg, their relative affinities for Tg are comparable. Likewise, mAb B10H2 appears idiotypically similar to mAb 62 because it totally inhibits the binding of mAb 62 to homologous anti-idiotype. Finally, as previously shown for mAb 62, mAb B10H2 expresses Id62 independently on both heavy (H) and light (L) chains, as evidenced by the immunoblot binding of a specific anti-Id62 probe to separated H and L chains. By molecular genetic analysis both antibodies appear to have made use of a member of the same VH 7183 gene family. Altogether, these findings suggest that neonatal mAb B10H2 and adult mAb 62 are very similar if not identical, and regulatory idiotype Id62 may be germline encoded. Furthermore this observation supports, in general, the concept of an idiotype-driven regulation for autoimmune responses.     

Human B cell lines can be triggered to secrete an interleukin 2-like molecule

To determine whether human B cells can be triggered to secrete interleukin 2 (IL-2), 19 tumor cell lines derived from patients with undifferentiated lymphomas of Burkitt's and non-Burkitt's types and 6 normal lymphoblastoid cell lines were tested. Cells were grown in the presence or absence of the new tumor promoter teleocidin, and culture supernatants were assayed for IL-2 activity using the standard CTLL-2 assay. Teleocidin (10 ng/ml) triggered IL-2 secretion in 7/8 (87%) EBV-negative lymphoma cell lines of American origin and in 6/6 (100%) normal lymphoblastoid cell lines, but in only 1/6 (16%) EBV-positive tumor cell lines of American origin. Teleocidin had no effect on 5/5 (0%) African Burkitt's cell lines. IL-2 secretion was not detected in control supernatants. IL-2 secretion correlated with the induction of IgM secretion and was linked to both EBV status and karyotype. The following similarities in the functional biological characteristics of T cell and B cell IL-2 suggest that B cell IL-2 is not a factor which mimics IL-2 activity in the CTLL-2 assay: (i) neutralization of IL-2 by anti-IL-2 monoclonal antibody (DMS-1); (ii) elution of IL-2 following its adsorption to CTLL-2 cells; (iii) determination of the MW of IL-2 by SDS-PAGE and Western blot analysis; and (iv) ability of B cell IL-2 to support T cell proliferation and blocking of this activity by anti-tac monoclonal antibody. cDNA probes for T cell IL-2, however, did not detect IL-2 mRNA in B cells. The cell lines were also found to constitutively express IL-2 receptors detected by anti-tac monoclonal antibody, and to secrete soluble IL-2 receptors measured by ELISA. Our results imply that under certain circumstances, B cells can be triggered to secrete IL-2 or an IL-2-like molecule and thus influence T cell activation and proliferation.     

Expression of idiotype on the surface of human B cells producing anti-DNA antibody

We analyzed the idiotype (Id) expression on the surface of human anti-DNA antibody-producing cells. Murine monoclonal anti-Id antibodies with a specificity for determinants associated with the antigen-binding sites of human monoclonal anti-DNA autoantibodies were prepared. One anti-Id antibody reacted only with surface Id on anti-ssDNA-producing cells, but not with those on anti-dsDNA-producing B cell clones. Another anti-Id antibody did bind the surface Id on anti-dsDNA clones, but not those on anti-ssDNA clones. The interaction between anti-Id and surface Id was inhibited by pretreatment of the clones with DNA or appropriate polynucleotide antigens, or by preabsorption of anti-Id antibodies with free anti-DNA antibodies. Surface IgM and IgD expressed the same Id as the antibody secreted from the clones. The treatment of Id-positive clones by anti-Id antibody induced the redistribution of surface Id on the cells, indicating that these cells serve as targets for the regulatory action of anti-Id antibody.