Localization of receptors and early events of phagocytosis in the macrophage

We studied the attachment of MRBC, 1.1 μm latex (foreign surface receptor), hemocyanin-DNP antiDNP Ab and sensitized SRBC (Fc receptor) to mouse peritoneal macrophages in culture, and the phagocytosis of 1.1 μm latex, AbAg complex, and sensitized SRBC by macrophages. Both types of receptors appeared over the whole cell surface. The particles attached mostly in the central area of the cell, but peripheral attachment was also observed. Internalization of 1.1 μm latex beads appeared to be mostly perinuclear, by sinking in of the cytoplasm with the attached particles, rather than a flow of membrane process over the beads. Also in the case of the AbAg complex attached to the Fc receptor internalization seemed mostly perinuclear and similar in mode to the latex ingestion. When attachment occurred in the periphery, active ruffling was observed. Sensitized SRBC internalization was seen mostly in the extreme periphery of the cells after the attached SRBC were moved from the perinuclear area where many of them first attached.