MPO and melanoma: Subcutaneous tissues from animals co-injected with apoptotic cells (106) and viable melanoma cells (103) and treated with PAF receptor antagonist PCA4248 or PBS (control) were surgically removed after 6 h, 24 h, and 72 h of the co-injection to evaluate the infiltration of macrophages and neutrophils by immunohistochemical analysis for MPO expression, as marker of neutrophils and F4/80, as marker of macrophages.