A potassium ionophore (valinomycin) inhibits lymphocyte proliferation by its effects on the cell membrane.

Valinomycin is a depsipeptide antibiotic which selectively translocates potassium across biologic membranes. This potassium ionophore was observed to inhibit phytohemagglutinin-stimulated blastogenesis and proliferation in human lymphocytes. The effect was not due to toxicity to the cells, nor appeared to be due to the effects of valinomycin as an uncoupler of oxidative phosphorylation. Furthermore, the inhibitory effect on phytohemagglutinin stimulated lymphocytes was prevented by increasing the potassium concentration of the external media. These results suggest that the interaction of mitogens with specific receptors at the cell membrane may involve mechanisms affecting cation fluxes and membrane potential. These ionic events may play a role in the transduction of membrane signals for lymphocyte stimulation.