Sustained increases in cytosolic calcium during t lymphocyte allosensitization, proliferation, and acquisition of locomotor function

Activation of resting T cells is accompanied by an increase in cytosolic calcium ([Ca²⁺]_I) ’ However, the role of [Ca2⁺]₁in the effector function of allosensitized cells, and how this may affect the evolution of the allograft response is unknown. To evaluate this more directly, we determined [Ca²⁺]_Iin both unsensitized T cells (C57BL/ 6 murine thymocytes) and in allosensitized T cells derived from different days of a C57BL/6 anti-DBA/2J mixed leukocyte culture. To correlate potential changes in [Ca²⁺]_I with concomitant development of T cell effector function, the [Ca²⁺]_I proliferation³HTdR uptake), and random locomotion (in vitro modified Boyden chamber assay) of the same cells was assayed simultaneously. Allosensitized T cells exhibited higher (P<0.05) [Ca²⁺]_Ithan unsensitized thymocytes on all days of culture tested. Further, there was a progressive rise in [Ca²⁺]_Iduring the course of allosensitization. Con A stimulated an increase in [Ca²⁺]_Iover basal levels (P<.05) for allcell types. A rise in [Ca²⁺]_Ipreceded the onset of maximal allosensitized T cell proliferation (which peaked at day7) and this continued to increase even after completion of DNA synthesis. In contrast, optimal T cell locomotion coincided with maximal [Ca²⁺]_Iwell after cell divisionhad occurred. Prostaglandin E₂, a known inhibitor of lymphocyte function, did not alter either basal or Con A-stimulated [Ca²⁺]_Iin thymocytes or MLC cells. These results indicate that [Ca²⁺]_Isignaling persists long after initial T lymphocyte alloactivation, and is maintained during DNA synthesis and acquisition of locomoto capacity.Furthermore, the inhibitory effects of PGE₂on allosensitized T lymphocyte function may be mediated by a calcium-independent mechanism.