Generation and characterization of cloned T helper cell lines for anti- DNA responses in NZB.H-2^bm12 mice

We have previously demonstrated that the introduction of the bm12 mutation into NZB mice results in animals that spontaneously produce high titer IgG autoantibodies to dsDNA. The observation that NZB.H-2^bm12 develop lupus although NZB.H-2^b control mice do not, provides a unique system to study the role of Th cells in the production of antibodies to dsDNA. We have isolated, in the absence of a known stimulating autoantigen, a series of seven autoreactive T cell clones that provide help in vitro for the production of IgG anti-dsDNA antibodies by syngeneic B cells. The data on these seven cloned T cell lines was compared to two cloned T cell lines specific for keyhole limpet hemocyanin. The seven cloned T cell lines, coined clones 19D, 23G, 410F, 410H, C1, C15, and C52 all show significant help in vitro for production of IgM and IgG antibodies to ssDNA and dsDNA; antibody levels increased 7- to 30-fold compared to cultures without T cells. Clones C1, C15, and C52 were furthered studied and were shown to provide help for IgM antihistone and anti-OVA responses but provided significantly less help for IgG antibodies. In contrast, keyhole limpet hemocyanin-specific cloned T cell lines TK2 and TK5 provided help for IgM antibodies to ssDNA, dsDNA, and histone, but failed to significantly increase IgG antibodies to ssDNA, dsDNA, or histone. The cloned T cell lines were restricted to H-2^bm12 and proliferated only in response to APC from NZB.H-2^bm12 and B6.C-H- 2^bm12 but not NZB.H-2^b or NZB.H-2(d) mice; their in vitro helper activity was inhibited by antibodies to class II. All cloned T cell lines expressed Thy-1, CD5, and TCR-α/β. Three of the seven clones used TCR- Vβ4. However, the Vβ expression of the four remaining autoreactive T cell clones could not be determined. All of the autoreactive cloned T cell lines produce significant IL-4 but no detectable IL-2 or IFN-γ. We believe that HPLC-purified peptides eluted from I-A^bm12 molecules from APC can potentially provide insight on the putative autoantigen.