Abstract
Summary
Protein A of Staphylococcus aureus reacts with the Fc portion of γG globulin molecules. Rabbit and human lymphocytes were studied in an attempt to document the effects of interactions between protein A and immunoglobulin receptors on such cells. Addition of protein A to lymphocyte cultures simultaneously with stimulating amounts of anti-lymphocyte antiserum, pokeweed mitogen, or phytohemagglutinin resulted in blockade of lymphocyte transformation. If lymphocytes were preincubated with protein A, washed and exposed to the same mitogens, depression of subsequent cell transformation was also noted. No lymphocyte stimulation was noted when protein A was added to cell cultures. Rather than exerting any stimulatory effects on lymphocytes, it is suggested that protein A of S. aureus may function as an immunosuppressant.
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