LIFE-SPAN OF GAMMA DELTA T-CELLS

Information on the turnover and lifespan of murine gamma/delta cells w as obtained by administering the DNA precursor, bromodeoxyuridine (Brd U), in the drinking water and staining lymphoid cells for BrdU incorpo ration. For TCR-gamma/delta (V gamma 2) transgenic mice, nearly all ga mma/delta thymocytes became BrdU(+) within 2 d and were released rapid ly into the peripheral lymphoid tissues. These recent thymic emigrants (RTEs) underwent phenotypic maturation in the periphery for several d ays, but most of these cells died within 4 wk. In adult thymectomized (ATx) transgenic mice, only a small proportion of gamma/delta cells su rvived as long-lived cells; most of these cells had a slow turnover an d retained a naive phenotype. As in transgenic mice, the majority of R TEs generated in normal mice (C57BL/6) appeared to have a restricted l ifespan as naive cells. However, in marked contrast to TCR transgenic mice, most of the gamma/delta cells surviving in ATx normal mice had a rapid turnover and displayed an activated/memory phenotype, implying a chronic response to environmental antigens. Hence, in normal mice ma ny gamma/delta RTEs did not die but switched to memory cells.