In vitro- and ex vivo-derived cytolytic leukocytes from granzyme A x B double knockout mice are defective in granule-mediated apoptosis but not lysis of target cells.
Granzyme (gzm) A and gzmB have been implicated in Fas-independent nucleolytic and cytolytic processes exerted by cytotoxic T (Tc) cells, but the underlying mechanism(s) remains unclear. In this study, we compare the potential of Tc and natural killer (NK) cells of mice deficient in both gzmA and B (gzmAxB-/-) with those from single knockout mice deficient in gzmA (-/-), gzmB (-/-), or perforin (-/-) to induce nuclear damage and lysis in target cells. With the exception of perforin-/-, all in vitro- and ex vivo-derived Tc and NK cell populations from the mutant strains induced 51Cr-release in target cells at levels and with kinetics similar to those of normal mice. This contrasts with their capacity to induce apoptotic nuclear damage in target cells. In gzmAxB-/- mice, Tc/NK-mediated target cell DNA fragmentation was not observed, even after extended incubation periods (10 h), but was normal in gzmA-deficient and only impaired in gzmB-deficient mice in short-term (2-4 h), but not long-term (4-10 h), nucleolytic assays. This suggests that gzmA and B are critical for Tc/NK granule- mediated nucleolysis, with gzmB being the main contributor, while target cell lysis is due solely to perforin and independent of both proteases.
Simon
M M
MM
Max-Planck-Institut für Immunbiology, Freiburg, Germany. simon@immunbiol.mpg.de
Hausmann
M
M
Tran
T
T
Ebnet
K
K
Tschopp
J
J
ThaHla
R
R
Müllbacher
A
A
D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D003594:Cytoplasmic Granules / Q000201:enzymology* / Q000276:immunology; D003601:Cytotoxicity Tests, Immunologic; D003602:Cytotoxicity, Immunologic; D053938:DNA Fragmentation; D005260:Female; D053804:Granzymes; D007939:Leukemia L1210; D008223:Lymphoma; D008297:Male; D012515:Mast-Cell Sarcoma; D008562:Membrane Glycoproteins / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D012697:Serine Endopeptidases / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology* / Q000276:immunology / Q000378:metabolism; D014407:Tumor Cells, Cultured
D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D054353:Perforin; D053804:Granzymes; C509214:Gzmb protein, mouse; D012697:Serine Endopeptidases