GAMMA DELTA T-CELLS IN FETAL, NEONATAL, AND ADULT-RAT LYMPHOID ORGANS/

In the present study, we have analyzed the appearance and maturation o f gamma/delta T cells, recognized with a new mAb V65, in the central a nd peripheral lymphoid organs of fetal, neonatal, and adult Wistar rat s. Cytofluorometrical analysis demonstrated the first V65(+) gamma/del ta T cells in the thymus of 16-17-day embryonic rats, although by immu nohistology, they were identified only in 19-day rat embryos in both t he cortico-medullary border and thymic medulla. Phenotypically, gamma/ delta thymocytes from fetal and neonatal thymus expressed CD3, CD2, an d CD5, but only 60-80% were CD8(+) and approximately 40-50% expressed the a chain (p55) of the IL-2R. In the periphery, the immunohistologic al study identified for the first time gamma/delta T cells in the sple nic white pulp and the gut of 21-day fetal rats, where they occurred w ithin the epithelium as well as in the lamina propria. After birth, ga mma/delta lymphocytes appeared in the skin, where they were present as dendritic epidermal T cells in increasing numbers during postnatal li fe. Whereas these gamma/delta T cells formed the predominant T-cell po pulation in the rat skin, gamma/delta T cells in peripheral lymphoid o rgans, BALT, or the gut only represented a minor T-cell population. Th ese results are discussed in comparison to gamma/delta T cells of othe r vertebrate species.