Specificity of antibodies for T sites and F sites of streptolysin O.

Antistreptolysin antibody (ASO) inhibits haemolysis of erythrocytes coated with streptolysin O (SLO), but antistreptolysin activity may also be due to the presence in sera of peptide fragments of altered beta lipoproteins. SLO-mediated haemolysis results from activity of a molecular site (the t site) distinct from that at which the SLO becomes attached to the cell (the f site), and both sites might be expected to function antigenically. Absorption studies with SLO-coated latex particles, and with SLO-coated erythrocytes in the cold, provide evidence for the existence of both classes of antibody. Results also suggest explanations for the frequent observation of false-negative and false-positive latex tests.