Immunocytochemical evidence for 3',5'-cGMP and 3',5'-cGMP-dependent protein kinase involvement in lymphocyte proliferation.

In preliminary experiments cyclic nucleotides and cyclic nucleotide-dependent protein kinase subunits were localized in murine splenocytes using immunofluorescence and immunoperoxidase techniques. Cyclic nucleotides, presumably protein bound, and protein kinases (PK) were found in both cytoplasm and nucleus. Following mitogen stimulation the localizations did not change. In experiments reported here using the peroxidase-antiperoxidase technique not all cells in the population were stained with antisera against the various antigens. At early times (5-60 min) following stimulation with lipopolysaccharide (LPS) or concanavalin A (ConA) the fraction of cells staining positively for cGMP and cGMP PK increased relative to non-stimulated cells. Radioimmunoassay measurements showed elevated intracellular concentrations of cGMP beginning at 15 min following mitogenic stimulation. The data presented is consistent with a role for cGMP and cGMP PK in lymphocyte activation.