Serological cross-reaction between rodent malaria parasites as determined by the indirect immunofluorescent technique.

In view of the morphological similarity between the blood stages of Plasmodium berghei berghei and P. b. yoelii on the one hand and P. vinckei and P. chabaudi on the other, these rodent malaria parasites were investigated by the indirect fluorescent antibody technique in the hope of thus differentiating between them.Sera were obtained from rats hyperimmunized against these four parasites, from rabbits immunized against the soluble antigens of the blood stages of the parasites, and from a rabbit immunized against the sporozoites of P. b. yoelii. The titre of each serum was determined by its reaction with the homologous and the heterologous antigens in a modified immunofluorescent technique.The results showed a definite cross-reaction between the four parasites, indicating a common antigen; no serological difference between P. b. berghei and P. b. yoelii (these being considered the berghei group or Group 1); no serological difference between P. vinckei and P. chabaudi (vinckei group or Group 2); and a definite serological difference between Group 1 and Group 2 infections.The theoretical antigenic structure of rodent plasmodia is discussed in the light of these findings.