SUSCEPTIBILITY OF INBRED STRAINS OF MICE TO TRYPANOSOMA-CONGOLENSE - CORRELATION WITH CHANGES IN SPLEEN LYMPHOCYTE POPULATIONS

  • 1 January 1978
    • journal article
    • research article
    • Vol. 32  (1) , 25-40
Abstract
A comparison was made of the susceptibility of 8 inbred strains of mice to infection with T. congolense. Marked differences in susceptibility as judged by survival were found between the different strains. The capacity of certain strains to survive longer than others appeared to be related to their ability to limit the numbers of trypanosomes in the circulation. There was no difference in the infectivity of T. congolense for mice of high and low susceptibility. The findings of similar prepatent periods suggested that the initial replication rate was similar in the different strains. The level of parasitemia in different strains of mice may reflect differences in the nature or quality of the immune response to the trypanosome. In all of the strains of mice a marked increase in splenic B [bone marrow-derived] and null lymphocytes was found. This, allied to the finding of an increase in the background plaque-forming cells to sheep erythrocytes, indicated that trypanosome infection results in a non-specific polyclonal activation of lymphocytes, and that this affects primarily B lymphocytes. In strains of mice which survived longest, i.e., C57Bl/6J and AKR/A, the increase in splenic B and null cells was less marked. Whether this is associated with a decreased susceptibility of these strains to polyclonal activation induced by trypanosome infection, or whether it is merely the result of lower levels of parasitemia, remains to be determined. By comparing T. congolense infection in 3 strains of mice congenic at H-2 locus, representing H-2a, H-2b and H-2k haplotypes, it was found that the susceptibility was not associated with the H-2 haplotype. The finding that (A/J .times. C57Bl/6J)F1 hybrids were of similar susceptibility as the C57Bl/6J parents indicated that the relative resistance of this strain is inherited as a dominant trait, although in the early stages of infection the F1 hybrids consistently showed somewhat higher levels of parasitemia than the C57Bl/6J mice. Athymic nude mice and surgically splenectomized mice were more susceptible to T. congolense infection than intact mice of the same strain. The effect of splenectomy was much less pronounced in C57Bl/6J mice than in the relatively more susceptible BALB/c/A mice.