ABSTRACT

Well known effector functions triggered by cross-linking of the human IgA receptor FcαR (CD89) expressed on neutrophils, monocytes and Mø, include phagocytosis, granule enzyme exocytosis, and NADPH oxidase activation. Recent evidence suggests that endocytosis and MHC class II presentation of CD89- targeted exogenous antigen by antigen presenting cells (APC) to T cells is another CD89-triggered effector function. Therefore, CD89 cross-linking triggers both exocytic and endocytic vesicle trafficking events in different cells to elicit distinct biological effects. These diverse effector functions are dependent on CD89- triggered signal transduction mediators, including PI 3- kinase, PDK1, PKBα and PKC that are also known regulators of vesicle trafficking events in other systems. The details of how CD89 signaling influences different vesicle trafficking events is not well known. In this article, we review existing data and propose a testable hypothesis that different CD89 effector functions are determined by the cell type and that common elements of CD89 signal transduction regulates the underlying endocytic or exocytic vesicle biology.