Structural diversity of Plasmodium falciparum gp200 is detected by T cells

T lymphocyte clones (TLC) specific for P. falciparum gp200 (a glycoprotein precursor of the main merozoite surface component) were obtained from two individuals with past exposure to malaria. The 25 established TLC carried the CD4 antigen and proliferated in the presence of immunopurified gp200, crude lysate of the parasite and intact infected red blood cells. They were further tested in proliferation assays for their capacity to recognize the structural diversity displayed by gp200. The stimulating antigen used in these assays was either sonicated or viable preparations of schizonts from five P. falciparum isolates differing in their gp200. The majority of the TLC proliferated similarly in the presence of each of the isolates. One third of the TLC proliferated to a different extent depending on the isolate used for stimulation, while two clones gave isolate-specific responses. These results indicate that the majority of human TLC raised in vitro against gp200, is directed against common determinants. This also suggests that immunization with full length gp200 will not lead predominantly to T cell help restricted to isolate-specific determinant.