Partial Protection of Severe Combined Immunodeficient Mice against Infection with Babesia microti by In vitro-Generated CD4⁺ T Cell Clones

Abstract

Because CD4⁺ T cells were considered to be involved in protection against infection with Babesia microti, specific CD4⁺ T cells were generated in vitro from recovered BALB/c mice and their protective activity was tested in vivo. The cells produced varying amounts of interferon (IFN)-γ in vitro in response to parasite antigen. In passive transfer experiments, three out of eleven T cell clones tested exerted protective activity in the early phase after infection. However, there seemed to be no correlation between this protection and in vitro IFN-γ production by the T cell clones. Although the protection was partial and short-lived, the result provided direct evidence that CD4⁺ T cells play a crucial role in defense against B. microti.