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Sustained increases in cytosolic calcium during T lymphocyte allosensitization, proliferation, and acquisition of
M L Jordan1, D F Vidgen, J Wright
1Department of Surgery, University of Pittsburgh, Pennsylvania 15213.
Insights
Cytosolic calcium ([Ca2+]i) increases in allosensitized T cells, persisting after activation and DNA synthesis. This calcium signaling is crucial for T cell effector functions like proliferation and locomotion during allograft responses.
Area of Science:
- Immunology
- Cellular Biology
- Calcium Signaling
Background:
- T cell activation involves increased cytosolic calcium ([Ca2+]i).
- The role of [Ca2+]i in allosensitized T cell effector function and allograft response remains unclear.
Purpose of the Study:
- To investigate the role of [Ca2+]i in allosensitized T cells.
- To correlate [Ca2+]i levels with T cell proliferation and locomotion.
Main Methods:
- Measurement of [Ca2+]i, proliferation (3HTdR uptake), and locomotion in unsensitized and allosensitized T cells.
- Utilized a mixed leukocyte culture (MLC) model.
Main Results:
- Allosensitized T cells showed significantly higher [Ca2+]i than unsensitized cells.
- [Ca2+]i progressively increased during allosensitization, preceding maximal proliferation and coinciding with optimal locomotion.
- Prostaglandin E2 did not affect basal or stimulated [Ca2+]i, suggesting calcium-independent inhibitory mechanisms.
Conclusions:
- [Ca2+]i signaling is sustained long after T lymphocyte alloactivation, supporting DNA synthesis and locomotor capacity.
- Calcium-independent pathways likely mediate Prostaglandin E2's inhibition of allosensitized T cell function.
Abstract:
Activation of resting T cells is accompanied by an increase in cytosolic calcium ([Ca2+]i). However, the role of [Ca2+]i in 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+]i in 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, proliferation (3HTdR uptake), and random locomotion (in vitro modified Boyden chamber assay) of the same cells was assayed simultaneously. Allosensitized T cells exhibited higher (P less than 0.05) [Ca2+]i than unsensitized thymocytes on all days of culture tested. Further, there was a progressive rise in [Ca2+]i during the course of allosensitization. Con A stimulated an increase in [Ca2+]i over basal levels (P less than .05) for all cell types. A rise in [Ca2+]i preceded the onset of maximal allosensitized T cell proliferation (which peaked at day 7) and this continued to increase even after completion of DNA synthesis. In contrast, optimal T cell locomotion coincided with maximal [Ca2+]i, well after cell division had occurred. Prostaglandin E2, a known inhibitor of lymphocyte function, did not alter either basal or Con A-stimulated [Ca2+]i in thymocytes or MLC cells. These results indicate that [Ca2+]i signaling persists long after initial T lymphocyte alloactivation, and is maintained during DNA synthesis and acquisition of locomotor capacity. Furthermore, the inhibitory effects of PGE2 on allosensitized T lymphocyte function may be mediated by a calcium-independent mechanism.