HERPESVIRUS SAIMIRI IMMORTALIZATION OF ALPHA-BETA AND GAMMA-DELTA HUMAN T-LINEAGE CELLS DERIVED FROM CD34(-VITRO() INTRATHYMIC PRECURSORS IN)

Herpesvirus saimiri (HVS), an agent that can infect many human cell ty pes, has been shown to immortalize selectively TCR alpha beta(+)CD3(+) T lymphocytes, Human T cell precursors defined as CD34(+)CD3(-)CD4(-) CD8(-) were isolated from thymic samples and exposed to HVS in the pre sence of either IL-2 or IL-7. Cultures lacking the virus were non-viab le by day 15, Test cultures, in contrast, showed a sustained prolifera tive activity lasting >5 months, allowing the phenotypical and molecul ar analysis of the cellular progeny, In the presence of IL-7, TCR alph a beta(+) cells with three different phenotypes (mainly CD4(+)CD8(-), but also CD4(+)CD8(+) and CD4(-)CD8(+)) were immortalized, whereas no TCR gamma delta(+) cells were recovered, Kinetic studies showed that t he expansion of immortalized TCR alpha beta(+) cells was preceded by a gradual loss of CD34(+) cells followed by a transient accumulation of two distinct cell subsets: first CD1(+)CD4(+)CD3(-) cells and then CD 4(+)CD8(+) thymocytes, This resembles early phenotypic changes occurri ng during normal intrathymic T cell development. In the presence of IL -2, in contrast, only TCR gamma delta(+) cells were immortalized (main ly CD4(-)CD8(+), but also CD4(-)CD8(-)). The results show that HVS can be used to read the CD3(+) cellular outcome of T cell differentiation assays, including gamma delta(+)CD4(-)CD8(-), gamma delta(+)CD4(-)CD8 (-), alpha beta(+)CD4(+)CD8(-), alpha beta(+)CD4(-)CD8(+) and alpha be ta(+)CD4(+)CD8(+) T cells, A clear role for different cytokines (IL-2 for gamma delta(+) cells, IL-7 for alpha beta(+) cells) in early T cel l commitment was also apparent.