Innate resistance to Babesia infection is influenced by genetic backgroundand gender

Infection of severe combined immunodeficient mice with Babesia sp. strain W A1 was studied to assess the contributions of innate and adaptive immunity in resistance to acute babesiosis. The scid mutation showed little effect i n genetically susceptible C3H mice and did not decrease the inherent resist ance of C57BL/6 mice to the infection, suggesting that innate immunity play s a central role in determining the course of Babesia infection in these st rains. In contrast, the scid mutation dramatically impaired resistance in m oderately susceptible BALB/c mice, suggesting that acquired immunity may pl ay an important secondary role. In comparison to their female counterparts, male mice of different genetic backgrounds showed increased resistance to the infection, indicating that the gender of the host may influence protect ion against babesiosis.