Development of surrogate cell adhesion receptors and their use in investigating the binding and triggering functions of cellular interaction molecules in macrophage-mediated cytotoxicity

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Microbiology and Immunology

First Committee Member

James S. Peacock - Committee Chair


Palmitate-derivatized antibodies were used as surrogate (cell adhesion) receptors (SR) to elucidate the role of junctional avidity as a regulatory mechanism in the selection of a target cell for antibody-independent and antibody-dependent macrophage-mediated cytotoxicity. SR molecules were incorporated into the membranes of macrophage populations at defined states of differentiation. The lipid anchor of SR precludes direct physical interactions between SR and intracellular signaling elements, enabling SR to promote effector-target cell conjugation without transmitting activation signals across the effector cell plasma membrane.FcR-independent SR mediated interactions between chicken erythrocyte (CE) targets and cells of the P388D1 M$\phi$ cell line, although unable to promote CE ingestion, resulted in efficient extracellular CE lysis. Similarly, M$\phi$ explanted from the peritoneal cavities of mice following 3-4 days of thioglycollate-induced peritonitis, which are in an intermediate stage of differentiation, exhibited significant SR mediated lysis of the CE targets. In contrast to P388D1 cells, however, the peritoneal exudate M$\phi$ (PEM) also exhibited efficient SR dependent CE internalization. These results demonstrate that a state of macrophage differentiation exists in which functional triggers of cytotoxicity are expressed on the effector cell surface but are ineffectual in initiating an attack on a target cell due to their inability to contribute sufficiently to the binding energy required to form stable effector-target cell interactions. The observation that PEM harvested within 1-2 days of thioglycollate induction, which are in a relatively quiescent state of activation, exhibited significantly diminished SR mediated lytic and phagocytic activities while able to effect efficient FcR-dependent effector function demonstrates that at this differentiation state in which macrophages do not express CE-specific post-binding function triggering receptors for either phagocytosis or extracellular lysis, FcR have required functions in both target cell recognition and effector cell triggering. In total, these results establish SR as a highly useful system for dissecting the requirements for productive interactions between two cells by uncoupling the attachment stage from post-binding biochemical sequelae.


Biology, General; Biology, Microbiology; Health Sciences, Immunology

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