REACTIVITY OF HYBRIDOMAS DERIVED FROM T-CELLS ACTIVATED IN-VIVO DURING GRAFT-VERSUS-HOST DISEASE

To examine the specificity of T helper cells activated during murine g raft-vs-host disease (GVHD), T cell hybridomas from GVHD spleens and l ivers were generated and analyzed. CTL-depleted C57BL/6 (B6) donor cel ls were injected into irradiated (B6 x bm12)F-1 or (bm1 x bm12)F-1 rec ipient mice. Five or fourteen days later, cells from livers and spleen s were fused directly with the TCR-deficient (alpha beta)(-) BW5147 th ymoma line. The in vivo-activated T cells produced hybridomas as effic iently as either T cells activated in a primary mixed lymphocyte react ion or expanded in vitro after isolation from GVHD mice. Overall, 91% (396 of 437) of hybridomas generated from GVHD animals responded to im mobilized anti-CD3 and 56% (220 of 396) of these hybridomas responded specifically to APC expressing host bm1 or bm12 alloantigens. More tha n 80% of bm12-specific hybridomas expressed CD4; all (53 of 53) of the bm12-specific hybridomas tested reacted to homozygous bm12 APC. Of th e alloreactive T hybridomas generated from B6-->(bm1 x bm12)F1 GVHD mi ce, 7% responded to bm1 APC. Five bm1-specific hybridomas were analyze d further. One CD4(+) hybridoma recognized a bm1 peptide presented by self I-A(b) and was blocked by anti-Ia Ab; the other four hybridomas, two of which also expressed CD4, responded to transfected L cells expr essing H-2K(bm1) and were not inhibited by anti-Ia Ab. These results i ndicate that a high percentage of CD4(+) T hybridomas generated from f reshly isolated T cells activated in vivo during GVHD are specific for host MHC class II or class I alloantigens.