Role of calcium influx in cytotoxic T lymphocyte lytic granule exocytosis during target cell killing.
One mechanism cytotoxic T lymphocytes use to kill targets is exocytosis of cytotoxic agents from lytic granules, a process that requires Ca(2+) influx. We investigated the role of Ca(2+) influx in granule exocytosis using TALL-104 human leukemic cytotoxic T cells triggered via a bispecific antibody containing an anti-CD3 F(ab') to kill Raji B lymphoma cells. Using a novel fluorescence method, we detected target-directed release of approximately 15% of lytic granules during killing. Consistent with previous work, we observed sustained CTL Ca(2+) gradients during killing, but gradients reflect the behavior of Fura-2 in granules. Rapid imaging experiments suggest that Ca(2+) channels are not polarized during killing, indicating that Ca(2+) influx does not direct granule reorientation. Furthermore, we find that Ca(2+) acts via a high-affinity interaction to promote granule exocytosis.
Lyubchenko
T A
TA
Department of Physiology and Biophysics, University of Colorado Health Sciences Center, 4200 East 9th Avenue, Denver, CO 80262, USA.
Wurth
G A
GA
Zweifach
A
A
D002118:Calcium / Q000276:immunology* / Q000378:metabolism; D003602:Cytotoxicity, Immunologic; D005089:Exocytosis / Q000276:immunology; D006801:Humans; D017136:Ion Transport / Q000276:immunology; D022142:Secretory Vesicles / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism
D002118:Calcium