Renal deposits of lipoprotein-immunoglobulin complexes in Plasmodium chabaudi-infected mice.

Lipoprotein metabolism is altered and immunoglobulin-lipoprotein complexes (Ig-Lp) are formed during malaria infection (1-5). Ig-Lp were detected in the sera of Plasmodium chabaudi-infected mice 9 days post-infection (1 or 2 days after parasitemia had peaked at about 50%) and reached a maximum on day 13 (when the parasitemia had decreased to less than 1%). Renal glomerular deposits of IgM were first detected at day 3 and were heavy from day 9 to day 29; deposits of IgG and low density lipoprotein (LDL) were present from days 9 to 62, and were more dense from days 22 to 29; deposits of C3 were observed from day 13 to day 29. Apoprotein B component was found in heparin eluates of kidneys on day 10, 14, and 29. Fractionated Ig-Lp, as well as whole sera from day-13 infected mice, were injected into uninfected mice that developed LDL glomerular deposits only when pre-treated with histamine. LDL glomerular deposits were also observed after i.v. injection of day-29 sera (containing free anti-lipoprotein antibody) into day-7 infected mice, but not when a mixture of day-29 and day-7 sera was injected into normal recipient mice. LDL glomerular deposits, however, were observed when recipient mice were treated with the Plasmodium-derived Insoluble Material (PDIM) 3 days before the injection of the day-29-day-7 sera mixture or day-13 serum. Two hours after the i.v. injection of 125I-Ig-Lp, the radioactivity of the kidneys was higher in histamine-treated, PDIM-treated, and P. chabaudi-infected mice than in controls. The clearance of 125I-Ig-Lp was higher in infected and in PDIM-treated mice than in controls. We suggest that the glomerular deposit of Ig-Lp that occurs during P. chabaudi infection requires an enhancing factor such as PDIM that is released during infection.