Low dose of deoxyguanosine increases IL-2 receptors of IL-2-dependent cultured T cells.

Deoxyguanosine ( dGuo ) is a purine nucleoside phosphorylase (PNP) substrate which has been shown to inhibit T lymphoblast growth, PHA-induced cell proliferation and suppressor T cell activity. Low dGuo concentrations (0.5-5 microM) increase interleukin-2 (IL-2) sensitivity of IL-2-dependent cultured T cells (CTC). dGuo alone has no direct mitogenic effect on CTC. The increased IL-2 sensitivity of CTC was more marked in the presence of low IL-2 concentrations than high ones. CTC incubated with dGuo at 37 degrees C for 24 hrs absorbed more exogenous IL-2 than control non-treated CTC. CTC incubated at 4 degrees in the presence of dGuo did not absorb any more IL-2 than control CTC. FACS analysis further showed increased Tac expression on CTC due to dGuo . These findings indicate that a 37 degrees incubation of CTC with dGuo increases the number of CTC IL-2 receptors. dGuo was not found to increase IL-2 production by PHA-stimulated PBM. Therefore, low dGuo concentrations selectively augment the sensitivity of cells responding to IL-2 by increasing IL-2 receptors.