title: Knob-positive and knob-negative Plasmodium falciparum differ in expression of a strain-specific malarial antigen on the surface of infected erythrocytes.
abstract: We have investigated the expression of a strain-specific malarial antigen on the surface of erythrocytes infected with knobless (K-) variants of knob-positive (K+) strains of Plasmodium falciparum. Aotus blood infected with K+ or K- parasites derived from two independent geographical isolates (Malayan camp and Santa Lucia) was surface iodinated by the lactoperoxidase method. Infected and uninfected erythrocytes were then separated by a new procedure involving equilibrium density sedimentation on a Percoll gradient containing sorbitol. Strain-specific antigens were readily identified on the surface of erythrocytes infected with either of the K+ strains by their characteristic size and detergent solubility. These proteins were not detected on the surface of erythrocytes infected with either of the K- variants nor on uninfected erythrocytes isolated from K+- or K- -infected blood. These results are consistent with a role for the strain-specific surface antigen in cytoadherence of P. falciparum-infected erythrocytes. Our findings represent the second biochemical difference (with the knob-associated histidine-rich protein) between K+ and K- P. falciparum.
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000032:analysis*; D004544:El Salvador; D000939:Epitopes; D004910:Erythrocyte Membrane / Q000276:immunology*; D008288:Malaria / Q000276:immunology*; D008296:Malaysia; D008565:Membrane Proteins / Q000097:blood / Q000302:isolation & purification; D010963:Plasmodium falciparum / Q000145:classification / Q000276:immunology*; D013045:Species Specificity
chemical_list: D000954:Antigens, Surface; D000939:Epitopes; D008565:Membrane Proteins