Antibody levels detected by the fluorescent antibody technique in mice infected with Plasmodium vinckei and P. chabaudi.

The malaria parasites of mice are convenient models for immunological studies. Plasmodium vinckei and P. chabaudi are similar parasites which behave differently in mice, the former invariably being fatal whereas the latter seldom kills the host. The experiments described in this paper were performed in order to compare the antibody levels in the Ig, IgM and IgG serum fractions in mice cured of P. vinckei infections and naturally recovered from P. chabaudi. The technique involved using specific labelled antimouse-Ig, -IgM and -IgG sera and had not previously been applied to malaria infections. The results showed that the patterns of antibody production were similar in cured and naturally recovered mice. IgG antibodies were involved from an early stage of the infection and IgM antibodies persisted throughout the period of experiment and even after challenge. These results are significant in that they indicate a pattern of immune response different from the classically accepted one and draw attention to the fact that even in highly immune animals considerable amounts of IgM may be present.