The levels of CD11b and CD18 fall dramatically following incubation with Leishmania under serum dependent (SD) culture conditions. Peritoneal macrophages were selected based on forward- versus side-scatter parameters as described in Materials and Methods and Figure 1 using flow cytometry. A) Isotype control with macrophages showing delineation of the M1 marker based on the negative population. B and C represent expression of CD18 (B) or CD11b (C) before incubation with Leishmania. D and E represent expression of CD18 (D) or CD11b (E) after association with Leishmania in a SD assay. In all cases the percent positive cells within the M1 marker are identified. This Figure is a representative diagram of 4 experiments with similar findings.