SINGLE-CELL PCR ANALYSIS OF TCR REPERTOIRES SELECTED BY ANTIGEN IN-VIVO - A HIGH MAGNITUDE CD8 RESPONSE IS COMPRISED OF VERY FEW CLONES

Taking advantage of a potent MHC class I-restricted response that allo ws the identification of antigen-selected CD8 T cells directly ex vivo , we characterized the antigen-specific T cell repertoires that develo p in individual mice by single-cell PCR analysis. Each of the immune m ice displayed distinct yet structurally similar TCR repertoires. The o verall repertoire size was estimated to be in the range of 15-20 for m ost mice. No major differences were observed between primary and secon dary responses. Moreover, for a hyperimmunized mouse the antigen-speci fic TCR repertoire expressed 8 months after the initial immunization w as very similar to that found at the peak of the primary response. Our results demonstrate that a high magnitude immune response may be comp osed of very few clones, and that at least in the system analyzed, the memory response largely reflects the repertoire selected by the peak of the primary response.