FIG. 4.
Experimental counts of the number of phagocytized microbes, PI (per 100 macrophages), as a function of the initial antibody concentration c0. IgG1 was incubated with C. neoformans cells for 1 h to obtain near-saturation occupancy of the binding sites on the C. neoformans capsule. C. neoformans cells were then separated from antibody and added to a macrophage monolayer in the fresh medium (see Materials and Methods). The two sets of results represent experiments without and with blocking of complement receptors. The results of experiments with blocking represented in panel A were obtained with partial blocking of complement receptors, and those in panel B were obtained with complement receptors fully blocked. Error bars represent standard deviations.