Aspirin-like drugs prime human T cells. Modulation of intracellular calcium concentrations

Aspirin-like drugs (ALD) enhance T cell proliferation by suppressing PG production in monocytes. Normal human T cells do not produce any eicosanoids. Therefore we studied whether ALD would affect purified T cells directly. We found that ALD enhanced the proliferation and IL-2 production of T cells in the absence of monocytes. This effect did not depend on arachidonic acid metabolism as no lipoxygenase products and only nonsuppressive levels of cyclooxygenase products were detected in T cell cultures. Several possible mechanisms of the ALD effect were ruled out including 1) enhanced mitogen binding, 2) induction of activation markers (IL-2R, transferrin receptor, HLA-DR) on the cell surface, 3) down-regulation of suppressor cells. ALD caused a rise in [Ca2+]i which appeared to reflect an influx of Ca2+ from the extracellular milieu and was more pronounced in CD4+ cells. The rise in intracellular levels of Ca2+, that is considered a necessary second messenger for T cell activation, may prime these cells for an enhanced response to mitogens. In addition, ALD increased T cell membrane fluidity but only at higher concentrations than those found to enhance proliferation. The pharmacologic effect of ALD on T cells presents a possible new immunoenhancing potential of these drugs and may have therapeutic use in immunosuppressed individuals.