Turnover and fate of I-Ak antigen on the murine macrophage cell surface

The macrophage plasma membrane is a major site of the cell's activities, including phagocytosis, antibody-dependent cellular cytotoxicity, and antigen presentation. To present antigen, the expression by the macrophage of immune region-associated (Ia) antigen is required. The turnover and fate of this cell surface constituent was studied in macrophages cultured with lymphokine or recombinant interferon-gamma. Surface-labeled subregion I-Ak antigen was lost from the cell surface at a rapid rate, with a half-life of approximately 24 hours. However, the shedding of I-A antigen into the culture fluid was not detected. Therefore, the loss of I-A antigen from the macrophage surface is most likely by its degradation. Upon removal of lymphokine or interferon from macrophage cultures, I-A antigen expression declined, with an apparent half-life of 2 days.