McKinney EC ; Flajnik MF ;

J Leukoc Biol vol. 61 (2)   pp. 141-6, Fev 1997

Department of Microbiology and Immunology, University of Miami School of Medicine, Florida 33101, USA.

Two types of cytotoxic reactions have been observed using cells from the nurse shark: spontaneous cytotoxicity mediated by cells of the macrophage lineage and antibody-dependent killing carried out by a different effector cell population. Previous data showed that removal of phagocytic cells using iron particles abolished macrophage-mediated killing, but not antibody-dependent reactions. The current study used single cell assays and showed that the effector of antibody-driven reactions was the neutrophil. Surprisingly, the mechanism of killing was shown to be phagocytosis mediated by both 7S and 19S immunoglobulin M (IgM). Reactions proceeded with as little as 0.01 microg of purified 19S or 7S IgM and were complete within 4-6 h. In contrast, purified immunoglobulin did not adsorb to macrophages and had no effect on target cell binding or cytotoxicity. Pretreatment of cells with cytochalasin D abolished the phagocytic reaction, but not spontaneous cytotoxicity. These data show that antibody-mediated killing results from opsonization and phagocytosis; the mechanism of macrophage killing is currently unknown. In addition, these data show that the shark neutrophil, not the macrophage lineage, carries a receptor for Fc mu.

Animal ;  Antibodies,Blocking: pharmacology ;  Antibodies,Monoclonal: pharmacology ;  Antibody Specificity ;  Antibody-Dependent Cell Cytotoxicity ;  IgM: biosynthesis: chemistry: physiology ;  Immunoglobulins,Heavy-Chain: pharmacology ;  Immunoglobulins,Surface: physiology ;  Killer Cells: immunology ;  Opsonins: immunology ;  Sharks: immunology ;  Support,U.S.Gov't,Non-P.H.S. ;  Support,U.S.Gov't,P.H.S. ;  25620 ;