Sheep-erythrocyte-capping by human T-lymphocytes. Pharmacological inhibition by phenothiazine drugs.

In our previous studies it was found that E-rosette dissociation and sheep-erythrocyte capping were active processes involving the cytoskeleton. These cellular functions are now shown to be very sensitive to phenothiazine-drugs whose activities can be differentiated as follows: trifluoperazine greater than chlorpromazine greater than sulfoxide derivatives, suggesting a role for calmodulin-mediated events. These findings are in contradiction to prior reports pointing to the inefficacy of chlorpromazine to inhibit slow kinetic capping. However, no co-capping of trifluoperazine fluorescence (as a probe of calmodulin) and sheep erythrocytes could be observed. No requirement in extracellular calcium was evident for E-rosette formation and dissociation.