IMMUNOLOGICAL RESPONSE OF CBA MICE TO P-YOELII .1. GENERAL CHARACTERISTICS, EFFECTS OF T-CELL DEPRIVATION AND RECONSTITUTION WITH THYMUS GRAFTS

Abstract

Experimental infection of normal CBA mice with the parasite Plasmodium berghei yoelii (P. yoelii) resulted in a mild, non-fatal and self-limiting infection which lasted for 15-17 days. Animals which recovered from the primary infection were immune to reinfection though parasites could be detected in the kidneys of such mice 4 wk after recovery from infection. (No plasmodia were demonstrated in the peripheral blood or other tissues examined.) In T [thymus-derived] cell-deprived mice, P. yoelii infections resulted in a progressive parasitemia and proved fatal in 35-40 days. Studies of fluorescent antibody levels and morphological changes in the spleens of infected normal and T cell-deprived mice showed that while normal mice produced high levels of Ig[immunoglobulin]G1, IgG2 and IgM antiplasmodial antibodies and developed a strong and sustained germinal center response, in T cell-deprived animals the production of IgG1 antibodies was almost completely abolished and the germinal center response severely impaired. Reconstitution of T cell-deprived mice with syngeneic thymus grafts resulted in partial restoration of immunological responsiveness. P. yoelii infections in these reconstituted animals ran a self-limiting course akin to that seen in normal CBA mice; the level of protective immunity and the germinal center response correlated with the degree of reconstitution achieved.