“…Whether immune phagocytosis plays a role in immunity to infection is not known but it would be reasonable to assume that it could do so provided that the conditions were suitable. Obviously, contact between cells and parasite is a prerequisite; the intestinal epithelium is fairly well supplied with macrophages and, in the case of E. tenella, E. necatrix, and E. acervulina, there is some evidence that sporozoites may be transported within macrophages to their developmental sites (3,5,7,15,24); therefore, contact between cells and parasite could occur readily in vivo. Sensitization of cells and/or parasites could be by circulating or by locally produced antibodies; local vascular permeability is increased at the time of infection, especially in immunized birds (11,20).…”