QUALITATIVE DIFFERENCES BETWEEN NAIVE AND MEMORY T-CELLS MAKE A MAJORCONTRIBUTION TO THE MORE RAPID AND EFFICIENT MEMORY CD8(-CELL RESPONSE() T)

CD8(+) T cells are present at a higher frequency following a primary r esponse, and these memory cells exhibit qualitative differences from n aive cells, The importance of these differences vs increased precursor frequency in making a memory response more rapid and efficient has be en unclear. Adoptive transfer of 2C TCR transgenic CD8(+) T cells into normal recipients, followed by i.p. challenge with allogeneic P815 tu mor, results in a long-lived memory population that includes both endo genous host CD8(+) T cells and 2C cells. The 2C cells can be identifie d, using 1B2 mAb specific for the TCR, and thus used as an indicator o f the properties of the memory cells, The memory cells have a heteroge neous surface phenotype, and their distribution in lymphoid organs, bl ood, and peripheral sites is distinct from that of naive cells. Upon r echallenge with Ag, memory cells access the peritoneal cavity much mor e rapidly than do naive cells (12 h vs 5 days). This appears to result from a requirement for naive cells to interact with Ag before they ca n efficiently migrate to inflammatory sites, while this is not require d for memory cells. In addition, memory cells exhibit some cytolytic a ctivity before rechallenge with Ag, and potent cytolytic activity is p resent in the peritoneal cavity within 12 h of rechallenge, Comparison of primary and memory responses in mice having similar frequencies of Ag-specific precursors demonstrated that the more rapid migration and the immediate effector function of at least some memory cells contrib ute very substantially to making a memory response at a peripheral sit e more rapid and efficient.