Functional defects of NK cells treated with chloroquine mimic the lytic defects observed in perforin-deficient mice.
NK cells are the primary effectors mediating acute rejection of incompatible bone marrow cell grafts. To reduce rejection, we evaluated the ability of chloroquine (CHQ) to prevent perforin-dependent NK cell activity. Perforin is a key cytotoxic component released from the lytic granules of activated NK cells. Generation of functional perforin requires an acidic protease activity that occurs in the secretory, lytic lysosomes. Our hypothesis was that CHQ, a lysosomotropic reagent, would raise the pH of the acidic compartment in which perforin is processed and thereby block perforin maturation and cytotoxicity. We have measured NK cytotoxicity in vivo by clearance of YAC-1 tumor cells from the lungs and by rejection of incompatible bone marrow transplants and in vitro by cytolysis of YAC-1 and Jurkat cells. The engraftment of bone marrow cells was monitored by recolonization of the spleen with hemopoietic cells from transplants of MHC class I-deficient bone marrow cells into lethally irradiated recipient mice. Transplant rejection was compared in two inbred strains of mice: 129, which apparently use perforin-dependent cytotoxicity, and C57BL/6, in which rejection can be perforin-independent. CHQ treatment reduced NK cell activity in 129 mice in which perforin is important for mediating rejection. CHQ affected the fraction of NK cell cytolysis that was Fas independent. In addition, we found that CHQ prevents perforin processing by LAK cells in vitro. These data indicate that CHQ may impair rejection of incompatible bone marrow transplants and other functions mediated by NK and cytotoxic T cells.
Austin Taylor
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Graduate Program in Immunology, Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. austin01@utsw.swmed.edu
Bennett
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Kumar
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Schatzle
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JD
D000818:Animals; D001854:Bone Marrow Cells / Q000187:drug effects / Q000276:immunology; D016026:Bone Marrow Transplantation / Q000276:immunology; D002465:Cell Movement / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D002738:Chloroquine / Q000494:pharmacology*; D003602:Cytotoxicity, Immunologic / Q000187:drug effects* / Q000235:genetics*; D053222:Fas Ligand Protein; D006084:Graft Rejection / Q000235:genetics / Q000276:immunology / Q000517:prevention & control; D015395:Histocompatibility Antigens Class I / Q000235:genetics; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007275:Injections, Intravenous; D019169:Jurkat Cells; D007694:Killer Cells, Natural / Q000187:drug effects* / Q000276:immunology* / Q000637:transplantation; D008024:Ligands; D008175:Lung Neoplasms / Q000276:immunology / Q000473:pathology / Q000517:prevention & control; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000172:deficiency* / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000276:immunology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D019014:fas Receptor / Q000378:metabolism
C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D015395:Histocompatibility Antigens Class I; D007166:Immunosuppressive Agents; D008024:Ligands; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D019014:fas Receptor; D054353:Perforin; D002738:Chloroquine