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The T‐Cell Receptor for Antigen: Past, Present and Future

expressed on antigen-specific suppressor molecules [7, 8]. On the basis of the present information this interpretation of the data cannot be either rejected or adopted. Possibility 3: the T-cell specificity repertoire is generated in ontogeny by selection for recognition of B-cell idiotypes. This interpretation is one that appeals to those used to thinking in network terms. Since in an idiotypic network each antibody molecule has both idiotypic and anti-idiotypic properties, a selection of the T-cell repertoire for affinity towards antibody combining sites would result in a reflection of the B-cell idiotypic spectrum by T cells. No genetic or structural relationships between T-cell receptors and antibodies have to be invoked in this model. It is, however, somewhat difficult to reconcile with the VH framework sharing unless one assumes that there is no sharp distinction between idiotypic and framework determinants. On the other hand, this interpretation is in agreement with experiments showing the existence of T cells that recognize B-cell idiotypes (summarized in Ref. 3). As for possibility 2, there is no formal evidence to reject this interpretation. Thus, the assumption of IgV gene expression in T cells was clearly justified, but only as one out of several hypotheses and not as proven fact. Particularly the failure to detect VH mRNA [5], supported by the failure to detect the rearrangements typical for expressed VH genes (summarized in Ref. 5), seems to have disproved this hypothesis, so that the other possibilities must now be considered.