Blood Cell Count Changes Associated with Immunity to Nematospiroides dubius

Abstract

Experimental mice were given 4 inoculations of 100 N. dubius larvae at 16-day intervals, and total and differential white blood counts were made every 4 days. Mice undergoing immune expulsion of worms exhibited an earlier onset, intensity, and duration of leukocytosis, a sharp reversal of the lymphocyte-neutrophil ratio, and a distinct eosinophilia. These results suggest that there is an association of such peripheral blood changes and immune reactions to N. dubius. Mice with an initial infection of Nematospiroides dubius are known to exhibit marked changes in their total and differential leukocyte counts, but a striking eosinophilia is not noted (Baker, 1962). The failure to show a strong eosinophilic response has been linked by Baker (1962) to the inability of the laboratory mouse to develop immunity to this parasite. However, in light of work by Van Zandt (1961), who reported the production of immunity in mice after three injections with 50 larvae, by Lueker et al. (1968), who demonstrated strong acquired immunity to this parasite after subcutaneous injection of 2,000 exsheathed third-stage larvae, and that by Panter (1969), who showed that there was an association between tissue infiltration with eosinophils with multiple infections, it was decided to study the blood changes in mice immunized by repeated infections. MATERIALS AND METHODS Experimental infections The methods of collecting and culturing eggs and infecting mice were essentially those of Van Zandt (1961). Sixty-four male S-W mice, 12 weeks old, were distributed randomly into 5 groups. Fifteen mice of group I (experimentals) and 8 mice of group IV (drug controls) were given 4 stimulating inoculations of 100 N. dubius larvae at 16-day intervals, whereas the 15 mice of group Received for publication 22 July 1971. *A portion of a dissertation submitted to the faculty of the University of North Carolina in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Parasitology and Laboratory Practice. This investigation was supported in part by a Postdoctoral Fellowship (1F02GM44719-01) from the National Institute of General Medical Sciences. III (single-infection controls) were not infected at this time. The 15 mice in group V (noninfected controls) were bled according to the schedule for groups I and III, but they were not challenged with larvae. The 12 mice of group II (viability controls) were included to check the viability of the larvae used in the 4 stimulating inoculations. Four were killed 16 days after each infection to make adult worm counts. Sixteen days after the third stimulating inoculation, the mice in groups I, III, IV, and V were given treatment with carbon tetrachloride (Van Zandt, 1961). The mice in group IV (drug controls) were killed 4 days after treatment, and counts were made of the number of adult N. dubius found in the small intestine of each animal. Four days after drug treatment, the mice of groups I and III were given a challenging inoculation with 100 N. dubius larvae. After 16 days, these mice were killed by cervical dislocation and counts were made of the numbers of adult worms residing in their small intestines. The mice of group V were not infected, since they were included to compare the blood picture in normal mice of the same age and sex.