A cross-reaction between Str. pyogenes and human fibroblasts, endothelial cells and astrocytes.

Antisera were raised in rabbits to whole streptococci of group A grown in a semi-synthetic medium, containing tryptic digest of casein. Twelve of these sera were tested for their ability to react with a variety of human tissues by the immunofluorescence technique. One serum, raised against a type 6 glossy strain, contained no detectable antibodies to the sarcolemmal/subsarcolemmal region of the myocardium, but gave strong staining of fibroblasts, endothelial cells, smooth muscle and the pia-arachnoid. In addition there was staining of astrocytes, best demonstrated in sections of an astrocytoma, and of the stratum granulosum of the skin. This reaction was prevented by absorption with the homologous organism but not with . In addition the titre of the serum against fibroblasts was not affected by the presence of 10 mg/ml tryptic digest of casein in the diluent. Antisera to two other strains of streptococci (type 6 matt and type 24) gave this staining reaction in addition to the sarcolemmal/subsarcolemmal staining reaction.