beta-Microglobulin is Bound to Streptococcal M Protein

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Abstract
The presence of receptors for 3 human proteins (fibrinogen, IgG and .beta.2-microglobulin (.beta.2m)) was studied in group A streptococcal strains, M type 1, 12 and 14 and in M protein-negative variants of these strains. Fibrinogen binding was detected in all 6 strains. IgG did not bind to the 2 type-12 strains and uptake was low in both type-14 strains. The type-1 M protein positive strain was negative in binding experiments with radiolabeled IgG, but the M protein-negative variant was strongly positive. Aggregated .beta.2m showed a high degree of reactivity with the M protein-positive strains but not with the corresponding M protein-negative variants. The results indicate that the receptor for aggregated .beta.2mis located on M protein in group A streptococci.