Staphylococcus aureus and protein A as mitogens for rabbit T lymphocytes.

The thymidine uptake by rabbit lymph nodes, spleen and peripheral blood lymphocytes was stimulated by Protein A (SpA) and SpA-containing staphylococci. The cell fraction enriched in T lymphocytes showed a higher degree of stimulation with SpA than the fraction enriched in B cells. Rabbit thymocytes showed a marked thymidine uptake by treatment with SpA but not with staphylococci. The monovalent fragment B of SpA (reacting with IgG) neither stimulated nor inhibited the incorporation of thymidine in rabbit lymph node lymphocytes indicating that the Fc reacting site of SpA cannot be responsible for the mitogenicity.