Recombinant mouse IL-6 boosts specific serum anti-plasmodial IgG subtype titres and suppresses parasitaemia in Plasmodium chabaudi chabaudi infection

C57BL/6 mice which were treated with recombinant mouse interleukin-6 (rmIL-6), 75 ng in 0.2 ml saline, i.p., 24 h before inoculation with Plasmodium chabaudi chabaudi and on day's one, two and th,ee could not control the primary acute parasitaemia but were able to suppress secondary parasitaemia significantly, peak of 3% and to reduce parasitaemia to subpatent levels within three weeks. Control C57BL/6 mice, which received saline injections only, developed two identical peaks of parasitaemia of at least 21% each, typical of a primary P. chabaudi chabaudi infection and cleared parasitaemia by day 28 post-inoculation. Serum levels of IL-6 measured in the fir st week by enzyme-linked immunosorbent assay were significantly higher (two-fold) in recipients compared to control mice. Anti-plasmodial IgG1, 2a and 2b titres were four to 16 times higher in rmIL-6 recipients than in the control mice. Reduction of parasitaemia to subpatency during the secondary phase of P. chabaudi chabaudi infection bl C57BL/6 mice is primarily antibody-mediated and rmIL-6 accelerates this process by boosting the levels of the required specific anti-plasmodial IgG subclasses of antibodies.