Effects of hydroxyurea on concanavalin-A-induced T-cell proliferation. Depletion of T-cell growth factor-reactive and -producing T lymphocytes.

The effects of eliminating cycling precursors by in vivo administration of high doses of hydroxyurea (HU) in populations of mouse spleen T lymphocytes were studied by membrane immunofluorescence identifying mature Thy 1+, Lyt 2- and Lyt 2+ cell populations and mitogen-induced T-cell growth factor (TCGF) production or reactivity to TCGF. HU treatment results in a sharp decrease in the total number of T cells in mouse spleen, indicating that about 50% of peripheral splenic T lymphocytes have a short survival time in vivo. This depletion is more marked for Lyt 2+ cells than for Lyt 2- cells. The decay of TCGF-reactive spleen cells after drug administration is similar to that of the overall spleen T-cell population. Conversely, production of TCGF induced by concanavalin A is predominantly affected by HU treatment, indicating a shorter life span of the cell(s) involved in TCGF production.