Lysis of antibody-coated cells by platelets.

Abstract

Antibody-coated erythrocytes are lysed by murine C5- whole blood but not by plasma separated from such blood. The lytic activity has been shown to derive from platelets that attach to sensitized cells probably through membrane receptors for C3b. Whole blood or platelet-rich plasma (prp) obtained from mice that have been treated with purified cobra venom factor has little or no activity unless it is fortified with fresh C5- plasma. Lysis is observed only if the reactants are incubated at 37 degrees C and mechanical shaking is practiced, at least intermittently, throughout the period of incubation. Adherence of platelets and subsequent lysis are mediated by antibodies of a variety of immunoglobulin classes, including those that fail to mediate complement-dependent lysis. Platelet-mediated lysis is limited to cells to which the platelets adhere; 51Cr labeled, unsensitized cells that are mixed with prp and sensitized, unlabeled cells do not release 51Cr. Normal murine lymphoid cells and ascites tumor cells of mice, rats, and guinea pigs were apparently unaffected by sensitization and incubation with prp. However, because adherence of platelets to these sensitized cells was not observed, it is not clear whether the cells are resistant to the lytic action of platelets or whether the conditions of incubation were unfavorable for the attachment of platelets to the surfaces of nucleated cells. The significance of the lytic reaction described here is not known but may lie in antibody mediated release of microbicidal substances from platelets.

Human platelet-mediated cytotoxicity against Toxoplasma gondii: role of thromboxane.

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65against antibody-sensitized sheep (13,14) and human (15) erythrocytes, schistosomula of Schistosoma mansoni (16)(17)(18), and microfilariae ofBrugia malayi (19) has been demonstrated in vitro. Platelet-mediated ADCC activity resides preformed in platelet membranes and may involve phospholipase A2 reaction products (20).

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Human platelet inhibition ofToxoplasma gondiigrowth

“…The medium used for the in vitro culture of T. gondii lacks mammalian immunoglobulins, and three of the four platelet donors did not have antibodies to T. gondii. Moreover, in the present study the results obtained with frozen and normal washed platelets, hrPDGF-AB, -AA, -BB and hrTGF-b1 suggest that antibodies to T. gondii cannot be involved in this human platelet-mediated cytoinhibition against the parasite as found in other systems [37][38][39][40].…”

Cytotoxic activity of peripheral blood platelets and mononuclears in cancer patients and healthy donors

“…It has been shown, for example, that platelets are capable of lyzing, together with complement, antibody-bound red cells and of causing the death of Schistosoma volvina and the lysis of tumor cells [2][3][4][6][7][8][9][10]. A cytolytic activity of platelets has been demonstrated for a number of tumor cell lines, including K-562, KU 812, and LU 99A [8].…”