Characterization of the mechanism of target cell recognition by natural cytotoxic (NC) effector cells using a cloned cell, L10A2.J : the role of tumor necrosis factor (TNF) and other determinants

Matsui, Neil M.
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Natural cytotoxic [NC] activity is a type of natural cell-mediated immunity that can kill transformed target cells in vitro and is an important mediator of immune surveillance of tumors in vivo. Here we have addressed the role of TNF in binding of NC effectors to target cells. The majority of work in the elucidation of NC effector mechanisms against transformed targets has been carried out with spleen cell NC effectors, i.e, a heterogenous population. We characterize a cloned NC effector, L10A2.J. L10A2.J is a B cell lymphoma that efficiently kills NC-sensitive targets in an 18-hour 51Cr-release assay. NC-resistant targets, including targets selected for resistance in vitro to spleen cells (10METO.4.4S.3) or tumor necrosis factor [TNF] (10METO.4.5T.1), and targets selected in vitro for tumor formation (L88) are also resistant to NC activity. Likewise, targets selected for resistance in vitro to L10A2.J (10ME.sL.6) are resistant to spleen cell NC activity and are tumorigenic in normal mice. Furthermore, L10A2.J has properties of NC activity and not of natural killer cells, cytotoxic T lymphocytes, or antigen-dependent cell-mediated cytotoxicity. Finally, L10A2.J-mediated killing is inhibited by antibodies against TNF-α, a lytic molecule of NC effectors. Several transformed cell lines of B lymphocyte lineage also are characterized as NC effectors. All of these B cell NC effectors require effector cell-to-target cell contact for killing to occur. Although 14 of 18 B cell lines tested have NC activity, elimination of B cells with antibody against immunoglobulin plus complement fails to eliminate splenic NC activity. Using L10A2.J as a cloned NC effector, an assay was developed to assess binding of NC effectors to targets. L10A2.J efficiently binds to 10ME target cells. L10A2.J.sT, a population of L10A2.J selected for reduced binding, has decreased binding to and killing of target 10ME cells. Binding of NC effectors to targets, is therefore important for efficient killing. Targets that have been selected by spleen cells (10METO.4.4S.3) or L10A2.J (10ME.sL.6) in vitro, or cells that have been selected for tumor formation in vivo (188) are bound less efficiently by L10A2.J than parent 10ME. Because 10METO.4.4S.3, 10ME.sL.6, and L88 also form tumors, binding of effectors and targets appears to be important in vivo for the immune surveillance of tumors by NC effectors. TNF is important as a lytic molecule for NC effectors. Killing by L10A2.J and other B cell effectors are substantially inhibited by antibody against TNF. Furthermore, binding of L10A2.J to 10ME can be partially reduced by antibody against TNF or by recombinant TNF. Inhibition of TNF binding to its receptor can reduce binding, but because the inhibition is not complete, it is likely that TNF is only one of many molecules involved in the binding of NC effectors to targets. In addition, binding of NC effectors to targets can be reduced by antibody that blocks the interaction of LFA-1 and ICAM-1, a common leukocyte adhesion system. The work described here reports two major findings that further our understanding of NC effector-mediated immune surveillance. First, several B cell lines have NC activity, and can be used as cloned NC effectors. Additionally, binding plays a role in the killing of target cells by effectors.
Thesis (Ph. D.)--University of Hawaii at Manoa, 1994.
Includes bibliographical references (leaves 111-122).
x, 122 leaves, bound ill. 29 cm
Cell-mediated cytotoxicity, Tumors -- Immunological aspects
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Theses for the degree of Doctor of Philosophy (University of Hawaii at Manoa). Microbiology; no. 3106
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