Fig. (5) Effects of SeMac on opsonophagocytosis of S. equi and GAS by horse (A) and human (B) PMNs, respectively. FITC-labeled S. equi and GAS bacteria (10⁷ c.f.u.) were treated without or with horse and human convalescent sera and incubated in the presence or absence of 100 µg/ml SeMac with 100 µl nonimmune horse and human blood, respectively, at 37^°C for 5, 10 or 20 min. Red blood cells were lysed using an Immunolyse kit, and percentages of PMNs with phagocytosed bacteria determined by flow cytometry are presented.