Twelve L3T4+ Ly-2.2- subclones, derived from 4 independent BALB/c T cell lines, responded to a combination of the I-Ed molecule and a synthetic peptide corresponding to residues 91-108 of the lambda light chain from BALB/c myeloma protein M315 (alpha, lambda 2). Peptide analogues in which the mutated residues Arg95 or Asn96 were exchanged with the corresponding germ-line-encoded Ser95 or Thr96 had an abolished or greatly reduced capacity to stimulate T cell clones. However, responses of subclones to an analogue where the mutated Phe94 was substituted with the germ-line-encoded Tyr94 revealed three specificity patterns: 5 clones reacted only with the lambda 2(315) peptide, 6 clones responded equally well to both peptides and a single clone reacted better with the Tyr94 analogue. Analysis of the T cell receptor beta-chain gene rearrangements disclosed 7 distinct rearrangements, identical rearrangements only being found for subclones originating from the same line. At least 3 different V beta genes were used. Subclones with identical or nearly identical peptide specificity, major histocompatibility complex-restriction and alloreactivity could differ in their V beta or J beta gene segment utilization.

Previous work has indicated that BALB/c T helper cells (Th) recognize an idiotope expressed on a 88-114/117 fragment of V lambda 2 of BALB/c myeloma protein 315. In the present study the antigenic structure of this idiotope was further analyzed. Conventional carrier-specific Th elicited by immunization of BALB/c mice with free lambda 2(315) did not cross-react with the free lambda 2 chain of the BALB/c myeloma protein T952 which differs from lambda 2(315) in five amino acid positions (38, 94, 95, 96, 99). Similarly, Th primed with free lambda 2T952 did not respond to a boost with free lambda 2(315). Thus, BALB/c lambda 2(315)-specific Th recognize an idiotope that depends on some or all of the residues at positions 94, 95, 96 and 99. Furthermore, free lambda 2T952 contains an idiotope immunogenic to Th that depends on some or all of residues 38, 94, 95, 96 and 99. Th recognition of the free lambda 2T952 idiotope was quenched upon H + L chain assembly because Th elicited by free lambda 2T952 did not respond to a boost with the complete T952 myeloma protein. In contrast to the lack of Th cell cross-reactivity, some of the antisera from BALB/c mice immunized with free lambda 2T952 cross-reacted with free lambda 2(315), free lambda lJ558 and free lambda 3CBPC49 but not with free kappa W3129 or polyclonal L chains. The H chain of T952 (alpha, kappa 2) myeloma protein was abnormally short (Mr = 48 000) and T952 existed as a halfmere probably due to this H chain deletion. Furthermore, H and L chains were disulfide bonded to each other.

Sera of some patients with systemic lupus erythematosus and related diseases contain a polyclonal antibody population (cross-reactive antinuclear antibodies [X-ANA]) that react specifically with both core mononucleosomes and plasma membranes of viable nucleated cells. Native mononucleosomes and nucleosome cores assembled from long DNA and the inner histones were indistinguishable in terms of inhibition of binding of X-ANA to nuclei of tissue sections and to polynucleosomes on the walls of plastic tubes. In contrast, mononucleosomes selectively depleted of histones H2A and H2B did not inhibit these reactions. A method was developed for isolation of X-ANA from serum that took advantage of the dual specificity of these antibodies. Immunosedimentation in sucrose density gradients revealed that 125I-labeled Fab' fragments of highly pure X-ANA formed complexes with the inner histones H2A, H2B, H3, and H4 in 2 M NaCL, but not in 0.15 M salt. These results indicate that X-ANA recognize an epitope of the inner histone in 2 M salt, and that in 0.15 M NaCL this epitope is not formed unless the histones interact with DNA to generate a nucleosome structure. Furthermore, in light of the previous demonstration that the epitope is destroyed by trypsin, it may be localized in the N-terminal region of histone H2A or H2B.

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.