The initial lag in phagocytic rate by macrophages in monolayer is related to particle encounters and binding.

Several investigators have described an initial "lag" in the phagocytic rates of macrophages in assay systems involving these phagocytes in monolayer. In the present study, we determined whether this apparent lag in phagocytic activity is due to a delay in the onset of macrophage phagocytic function per se, or if the lag phase can be explained by a relative lack of particle availability in terms of particle encounters and binding during the early phases of a phagocytic assay. Studies involving the pre-binding of opsonized erythrocytes to macrophages revealed that the lag in phagocytosis usually seen in assay systems involving macrophages in monolayer is related to particle availability.