IGE ELEVATION AND IGE ANTIMALARIAL ANTIBODIES IN PLASMODIUM-FALCIPARUM MALARIA - ASSOCIATION OF HIGH IGE LEVELS WITH CEREBRAL MALARIA

In the course of studying immunoregulation in human Plasmodium falcipa rum malaria we have investigated IgE levels and IgE anti-plasmodial an tibodies in children and adults from areas of high malaria endemicity in both Africa and Asia. On average, 85% of all donors had significant ly elevated levels of total IgE. A fraction of the IgE had anti-plasmo dial activity as revealed by ELISA with lysates of infected erythrocyt es as antigen. Using synthetic peptides representing antigenic regions of two major plasmodial blood stage antigens, IgE antibody concentrat ions ranged from 5 to 15 ng/ml serum for each of the peptides. On aver age, the concentrations of the corresponding IgG antibodies were x500- 1000 higher. Immunoblotting of parasite lysates showed that most donor s had IgE antibodies against one or several of a restricted number of plasmodial polypeptides, with antibodies against an antigen of mol.wt 45 kD already being present in all donors at an early age. Donors havi ng IgE antibodies to particular antigens also frequently had correspon ding IgG4 antibodies, reflecting underlying IL-4-dependent cellular me chanisms controlling formation of these isotypes. As infection with ot her parasites such as helminths is known to induce IgE elevation, the results do not prove that plasmodial infections were the primary cause of IgE induction. However, the importance of plasmodial infection for IgE elevation was supported by the finding of significantly higher le vels of IgE, but not of IgG, in children with cerebral malaria compare d with patients with uncomplicated disease.