Streptococcal receptors for human immunoglobulins

Six streptococcus strains with a high affinity for human serum Ig were examined under various experimental conditions to correlate their structures with specific IgG and IgA receptors. Treatment at 80 degrees C for 5 min appeared to have no effect on their ability to bind IgG and/or IgA, while long maintenance in culture determined a dissimilar partial loss of IgG and IgA binding ability. Proteolytic enzymes and hot HCl reduced the ability of these strains, especially those in group A, to absorb both IgG and IgA. It would seem that the protein most involved in this type of bond is the T protein.