Further evidence of a cross-reactive relationship between a cell wall antigen of certain Group A streptococcal strains and mammalian heart tissue is provided by the demonstration that goat antisera to washed human or rabbit heart tissue homogenates exhibit precipitation with cell wall extract preparations. A single line of precipitation was observed in agar gel diffusion tests. Precipitating activity of goat antiheart sera was related to the γ-globulin fraction in zone electrophoresis. The cell wall antigen was demonstrated in cell wall extracts of a Type 5 and Type 19 but not of a Type 12 strain. Antigenic activity was concentrated in the same neutral salt and chromatographic fractions of acid extracts of cell wall previously reported to exhibit this activity by immunofluorescent inhibition of the cross-reaction of antistreptococcal serum with heart tissue.
SummaryA proteinase was purified from a cell wall extract of a culture ofStreptococcus lactisNCDO 763 grown in skim milk. Being active at a low pH (at pH 4·8 on haemoglobin and pH 6·–6·5 on casein) and completely inhibited by diisopropylfluorophosphate, it was considered to be a serine proteinase partly inhibited by EDTA; the mol. wt was ∼ 80000.
IMMUNOLOGIC RELATION OF STREPTOCOCCAL AND TISSUE ANTIGENS
