Recognition of Syngeneic forms of L-Chain V-Region Peptides by T Helper Cells Suggests that B Cell Antigen Receptors are Processed and Reutilized in Cognate T-B Interaction

Idiotope-specific resistance to a malignant B cell line. We have worked with the monoclonal Ab produced by plasmacytoma 315, a high-rate Ab-producing malignant B-cell line originating in the inbred mouse strain BALB/c. We wondered whether T helper cells of BALB/c mice were capable of recognizing small peptides from the third hypervariable region (HV3) of the 315 L-chain. One reason for asking this question was that mice immunized with M315 develop resistance to challenge with a small number of 315 plasmacytoma cells that kill other mice immunized with another monoclonal Ab with the same H-chain C-region. Furthermore, the M315-immunized mice were killed by a small number of cells from another plasmacytoma that produced Ab with the same CH region as M315 (1). This indicated that the immune-mediated resistance to the tumor was directed towards V-regions, i.e. idiotopes, bound on the surface of the tumor cells (2).