H-2-RESTRICTED HELPER FACTOR SECRETED BY CLONED HYBRIDOMA CELLS

Biological and serological characteristics of a helper factor secreted by cloned mouse hybridoma cells was described. The factor is carrier specific and contains determinants shared with Ig VH [H chain variable region] but does not react with V.kappa.- or V.lambda.-specific antibodies. Presence of 4 H-21-controlled antigenic specificities, Ia.ml, Ia.m2, Ia.17 and Ia.m7, was detected. It is possible that both A.beta. and E.alpha. loci may be involved in its control. Helper effect could be obtained only toward B cell sources that shared the H-2K and I-A regions with the hybridoma cells. Similarly, the factor was absorbed only by spleen cells syngeneic in I-A. Previous studies have demonstrated that this clone binds antigen in an H-2-restricted manner. It follows that H-2-restricted helper cells produce H-2-restricted helper factors. This supports the view that specific T cell factors may represent secreted T cell receptors.