Cellular response and resistance to the primary infection of rats and mice with Nematospiroides dubius.

LEWIS rats, in contrast to NMRI mice, have been found to be resistant to an oral infection with Nematospiroides dubius (Baylis, 1926). Comparative studies of the peritoneal response to infection showed a strong increase in the cell number predominantly of eosinophilic and neutrophilic granulocytes in rats, whereas in mice only a weak reaction occurred. As shown by the chemiluminescence response to either antibody--or complement-coated larvae, the granulocyte reaction caused an increased production of toxic oxygen species by the peritoneal cells. Purified granulocytes from rats or mice showed about a ten-fold higher oxidant generation than macrophages. The higher metabolic activity of granulocytes of either species resulted in rapid and strong killing of antibody or complement-coated infective larvae by granulocytes of either species, whereas macrophages failed to express a significant larvicidal potency. From these results we concluded that the activated oxygen species derived from the metabolic burst of granulocytes are essential for an effective control of the primary infection with N. dubius. This suggests that the rapid and strong granulocyte response may form the basis of the resistance in rats. Thus, in mice, the ability of N. dubius to prevent the granulocyte response may serve as an escape mechanism of the parasite.