Altered immune responsiveness associated with Encephalitozoon cuniculi infection in rabbits.

The variation in immune response of two unrelated colonies of laboratory rabbits to high doses of heat-killed Brucella abortus strain 19 was investigated. One was a mixed-breed, multicolored colony in which a high prevalence of encephalitozoonosis had been recorded, whereas the other rabbits were derived from a colony of Dutch-marked specific-pathogen-free rabits. Although considerable variation in the immune response between individual rabbits was noticed at all bleeds, rabbits infected with Encephalitozoon cuniculi showed, on comparison with uninfected rabbits from either colony, a depressed immunoglobulin G response from week 5 of the antigen injection schedule and, from week 8, an elevated immunoglobulin M response.