Intestinal Mast Cell Response in Rats and Chickens to Coccidiosis, with Some Properties of Chicken Mast Cells

The response of intestinal mast cells to infection with coccidian protozoa in rats and chickens was compared with the well-known increase in the numbers of these cells which follows helminth infections. In <i>Eimeria</i>-infected chickens and rats given a moderate primary infection, there was an initial fall in the numbers of intestinal mast cells, small and insignificant in the rats, but more marked in the chickens. This was followed, towards the end of infection, by a return to (chicken) or an increase above (rat) normal levels. In birds given a large challenge inoculum of oocysts there was, within hours of dosing, an initial increase in numbers followed by a return to normal by day 2 and this response was similar in both immunised and susceptible birds. This rapid recruitment of cells was not seen in immune rats similarly challenged: in this species numbers were not increased until day 2 at the earliest. A marked increase in vascular leakage after the large challenge inoculum was apparent only in immunised birds. Thus this could not be correlated with the increase in numbers of mast cells which occurred equally in both immune and susceptible and was probably related to the invasion of host cells by the parasite. The mast cells of chickens are not degranulated by polymyxin B or compound 48/80, both of which affect rat mast cells. In the rat, connective tissue and intestinal mast cells differ in various ways including their dye-binding properties, but this was not seen with chicken mast cells.