Quantitative aspects of binding of canine serum immunoglobulins of Staphylococcus aureus protein A

Quantitative interactions of Staphylococcus aureus protein A (SPA) and canine immunoglobulins (Ig) are described. The S aureus Cowan strain I bound canine IgG, IgM, and IgA, whereas binding was not observed with the SPA-negative Wood 46 strain of S aureus. In a quantitative adsorption experiment, the results indicated that IgA, though present in the lowest amounts in the samples, appeared to be substantially bound by SPA. Adsorption of sera with SPA-negative Wood strain bacteria resulted in nonspecific protein losses in supernatants of 0% to 15%.