We examined lymphoproliferative response to phytohemagglutinin and ant
i-parasite antibody level in dogs naturally infected with Babesia gibs
oni. The dogs with subclinical B. gibsoni infection exhibited suppress
ed lymphocyte blastogenesis. Prominent depression of lymphocyte blasto
genesis and anti-parasite antibody production was observed in dogs suf
fering from relapses of clinical B. gibsoni infection.