Comparison of the mitogenic activities of streptococcal protein-G and staphylococcal protein-A on human mononuclear cells

In the present work we report data from experiments comparing the proliferative stimuli demonstrated by Streptococcal Protein-G and Staphylococcal Protein A on human peripheral blood mononuclear cells. Protein-G and Protein-A are presented to the cells in solution as well as linked to plastic or Sepharose beads, or incorporated within the cell wall of whole bacteria. The cellular response is measured by incorporation of 3H-thymidine in 72 hr cultures. The soluble and the immobilized forms of Protein-A, but not those of Protein-G, displayed high mitogenicity. Possible explanations for the absence of Protein-G induced mitogenicity are discussed.