Possible implication of Fc γ receptor-mediated trogocytosis in susceptibility to systemic autoimmune disease.

Leukocytes can "gnaw away" the plasma membrane of other cells. This phenomenon, called trogocytosis, occurs subsequent to cell-to-cell adhesion. Currently, two mechanisms of trogocytosis, adhesion molecule-mediated trogocytosis and Fc γ receptor-(Fc γ R-) mediated trogocytosis, have been identified. In our earlier study, we established an in vitro model of Fc γ R-mediated trogocytosis, namely, CD8 translocation model from T cells to neutrophils. By using this model, we demonstrated that the molecules transferred to neutrophils via Fc γ R-mediated trogocytosis were taken into the cytoplasm immediately. This result suggests that the chance of molecules transferred via Fc γ R-mediated trogocytosis to play a role on the cell surface could be time-limited. Thus, we consider the physiological role of Fc γ R-mediated trogocytosis as a means to remove antibodies (Abs) that bind with self-molecules rather than to extract molecules from other cells. This concept means that Fc γ R-mediated trogocytosis can be a defense mechanism to Ab-mediated autoimmune response. Moreover, the activity of Fc γ R-mediated trogocytosis was revealed to be parallel to the endocytotic activity of neutrophils, which was critically related to the susceptibility to systemic autoimmune diseases. The collective findings suggest that Fc γ R-mediated trogocytosis could physiologically play a role in removal of Abs bound to self-antigens and prevent autoimmune diseases.