T-HELPER LYMPHOCYTES RECOGNIZE THE VL-DOMAIN OF THE ISOLOGOUS MOUSE MYELOMA PROTEIN-315

The localization of a major determinant on an isologous myeloma protein (M315) which stimulates BALB/c helper T cells was investigated. Augmentation of the adoptive secondary antibody response to NIP‐M315 and the idiotype of M315 (ld315) was used as an indicator of helper effects. Spleen cells primed with the light chain of M315 (L315) and its V‐domain (VL315) were highly efficient helpers; priming with the fragment containing the two V‐domains of M315 (Fv315) induced a somewhat weaker helper effect than L315 or VL315. The helper effect was abolished or markedly reduced by treating the primed cells with rabbit anti‐brain theta + C. Cells primed with the heavy chain of M315 (H315) effected weak but significant help. The V‐domain of H315 (VH315) was incapable of eliciting cells with detectable helper effect. The data indicate that the VL315 embodies a major determinant for T helper lymphocytes. This determinant is expressed on the free VL315 as well as on the complete M315. In contrast, previous studies have shown that BALB/c antibodies produced against Id315 recognize antigenic sites that are only displayed on associated (VL315 VH315) domains. Copyright © 1979, Wiley Blackwell. All rights reserved