Activation of human lymphocyte subpopulations by protein A from Staphylococcus aureus bacteria

Cowan I strain Staphylococcus aureus bacteria were found to be mitogenic for human peripheral and cord blood lymphocytes. Experiments with lymphocyte supopulations otained by nylon wool filtration and/or E-rosette separation revealed that T-lymphocytes are the main target cells, whereas isolated B cells did not respond significantly. Further experiments suggested that B cells could be activated in the presence of mitomycin-treated T cells. Null cell-enriched lymphocyte suspensions could be stimulated by Con A but not by the bacteria or by PHA.