Effect of immunoglobulin M from normal human serum on Leishmania donovani promastigote agglutination, complement-mediated killing, and phagocytosis by human monocytes

T R Navin, E C Krug, R D Pearson
1989 Infection and Immunity  
Serum from healthy, nonimmune humans contained immunoglobulin M (IgM) antibodies that agglutinated Leishmania donovani promastigotes, activated complement, and enhanced promastigote ingestion by human monocytes. The findings indicate that IgM antibodies have the capacity to affect the initial interaction of L. donovani promastigotes with human host defenses. Early studies of the effects of nonimmune human serum on Leishmania donovani indicated that promastigotes are susceptible to
more » ... le to complement-mediated lysis following activation of the classical pathway (3, 6). The observations suggested that cross-reacting or natural antibodies are present in the sera of people who have not had prior exposure to L. donovani or other pathogenic members of the family Trypanosomatidae. We therefore explored the interaction between L. donovani promastigotes and components of normal human serum (NHS), especially immunoglobulin M (IgM). A Sudanese strain of L. donovani (MHOM/SU/00/S3) was cloned by limiting dilution and maintained by weekly passage in modified minimal essential medium to which 10% heat-inactivated (HI; 560C for 30 min) fetal bovine serum (FBS), penicillin, and gentamicin were added (1). Promastigotes were harvested in the mid-logarithmic phase, washed twice in phosphate-buffered saline (PBS), and resuspended in modified minimal essential medium at 106/ml. The concentration of motile, unagglutinated promastigotes was determined by counting in a hemacytometer the number of parasites that occurred singly or in pairs. Parasite viability was assessed by measuring the uptake of [3H]leucine or
doi:10.1128/iai.57.4.1343-1346.1989 fatcat:lv6rqezbvbae5p7vbb2yzakfii