Dipeptidyl peptidase I is enriched in granules of in vitro- and in vivo-activated cytotoxic T lymphocytes.
Recent studies have suggested that dipeptidyl peptidase I (DPPI) is the major post-translational processing enzyme responsible for generating activated myeloid and lymphoid granule serine proteases. The current studies assessed the relative levels of DPPI and granzyme A (BLT esterase) in B6 anti-H-2d-specific CTL generated in mixed lymphocyte cultures (in vitro-activated CTL), by infusion of B6 spleen cells into irradiated H-2d mice (graft-vs-host, GVH CTL) or by 1 degree and 2 degrees peritoneal immunization of B6 mice with P815 (H-2d) cells (PE CTL). In contrast to low levels of DPPI activity in unstimulated CD4+ spleen T cells, both unstimulated CD8+ spleen T cells and in vitro-activated CTL populations were several-fold enriched in DPPI activity, while PE CTL and GVH CTL expressed even higher levels of DPPI. Depletion of DPPI-enriched cells by treatment with Leu-Leu-OMe resulted in loss of cytolytic effector function from each CTL population. However, PE CTL and GVH CTL were more sensitive to the toxicity of Leu-Leu-OMe than were in vitro-activated CTL. While standard BLT esterase assays detected much higher levels of this serine protease activity in GVH CTL or in vitro-activated CTL than in PE CTL, levels of BLT esterase activity significantly above the basal levels present in unstimulated CD8+ or CD4+ T lymphocytes were found in association with immunoreactive granzyme A in lysates of PE CTL. In both PE CTL and in vitro-activated CTL, DPPI and BLT esterase activity co-localized in the granule fraction of cell lysates, and similar percentages of total cellular BLT esterase and DPPI were exocytosed upon cross-linking of surface CD3. Thus, both in vivo- and in vitro-activated CTL were found to possess functional granules containing readily detectable albeit somewhat different levels of DPPI and granzyme A activity.
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235.
G R
GR
Brown
M J
MJ
McGuire
D L
DL
Thiele
D000818:Animals; D001202:Ascitic Fluid / Q000276:immunology; D020789:Cathepsin C; D003594:Cytoplasmic Granules / Q000201:enzymology*; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D004151:Dipeptides / Q000494:pharmacology; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000378:metabolism*; D005260:Female; D053804:Granzymes; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D012697:Serine Endopeptidases / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology
D004151:Dipeptides; D007166:Immunosuppressive Agents; C045139:leucyl-leucine-methyl ester; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D020789:Cathepsin C; D053804:Granzymes; D012697:Serine Endopeptidases