Evidence that protein kinase C regulates allosensitized T lymphocyte function

The role of second messengers in the response of alloactivated T cells to growth factors (e.g., interleukin-2) is unknown. We have previously found that intracellular calcium may be an important T-cell alloactivation marker. To determine whether protein kinase C (PKC) is also involved in allosensitized T cell function, we studied the effects of the PKC agonists phorbol 12-myristate 13-acetate (PMA), mezerein (MEZ), and 1-oleoyl-2-acetylglycerol (OAG) and the PKC antagonists phloretin and D-sphingosine on the in vitro proliferation and migration of allosensitized cells from a C57BL/6 anti-DBA/2J mixed leukocyte culture (MLC). At 0.01-1.0 microgram/ml, PMA, a potent stimulant of PKC, exerted profound stimulatory effects on secondary MLC supernatant (2 degrees SN)-induced proliferation of allosensitized T cells (132-200% increase, P less than 0.01). Both MEZ and OAG are less potent activators of PKC than PMA but also stimulated T cell proliferation (132-152% of control, P less than 0.01). The PKC antagonists phloretin and D-sphingosine both inhibited proliferation by greater than 50% at 1.0-10.0 microM (P less than 0.01). Further experiments showed that these agents exert similar effects on in vitro T cell locomotion in a Boyden chamber assay. These data indicate that PKC activation may be an important component of allosensitized T cell proliferation and locomotion and may constitute a pathway by which T cell function may be modified in the allograft response.