The specificity of lymphocyte proliferative responses of malaria patients and healthy control subjects was analysed using antigen fractions from soluble extracts of purified Plasmodium falciparum schizonts. Fractions of 14-250 kDa were separated by SDS-PAGE, blotted to nitrocellulose membranes and eluted for use in lymphocyte stimulation studies. Lymphocyte proliferation following stimulation with the separated protein fractions demonstrated that the fractions were recognized only by patients' T cells. Moreover, only the fractions including proteins of 36-250 kDa were immunogenic to the T cells. The pattern of response against each fraction differed between patients, indicating an HLA-dependent genetic restriction in the T cell activation.