Suppression of primary antibody response to sheep erythrocytes in susceptible and resistant mice infected with Giardia muris.

The kinetics of anti-sheep erythrocyte (SRBC) response were studied in susceptible (A/J) and resistant (B10.A) mice during infection with Giardia muris. Mice infected with G. muris were found to be less responsive to either intraperitoneally or intraduodenally administered SRBC. Immunodepression was of relatively short duration, occurring during the period of highest trophozoite density in the small intestine, and was present in both spleen and, in particular, mesenteric lymph node cell populations. The main difference in the kinetics of anti-SRBC responses between A/J and B10.A mice was that susceptible mice were significantly less responsive to SRBCs than were the resistant B10.A animals. The difference in the kinetics of the anti-SRBC response between A/J and B10.A mice was not due to T-suppressor cell activity. Mesenteric lymph node cell transfers but not spleen cell transfers from infected mice to syngeneic recipients caused depressed normal anti-SRBC response. Furthermore, administration of the soluble extract of the trophozoites to uninfected mice resulted in a depressed response against SRBCs. Pronounced immunodepression in gut-associated lymphoid tissues may be more relevant than systemic immunodepression to survival and reproduction of trophozoites in murine giardiasis.