Mitogen induced cytotoxicity in the nurse shark

Nurse shark ( Ginglymostoma cirratum) leukocytes isolated from peripheral blood were demonstrated to possess cytotoxic activity towards xenogeneic marine erythrocyte targets (grey snapper) when stimulated by phytohemagglutinin, concanavalin A, or lipopolysaccharide. These leukocytes when separated on the basis of adherence to glass exhibited a differential cytotoxic effect. Only the adherent population showed significant cytotoxicity toward the target cells in the presence of any of the mitogens. Wright-Giemsa staining showed some differences in the two populations, however, both adherent and nonadherent cell populations contain all types of leukocytes. Upon surface marker analysis, the adherent cells were found to be depleted of sheep erythrocyte rosette forming cells and surface immunoglobulin positive cells compared to the nonadherent and unseparated populations. The cytotoxic reaction in the shark resembles that of mammalian species and the effector leukocyte(s) may be the phylogenetic precursor of mammalian cytotoxic effector cells.