Activation of lymphocytes in CLL by protein A from Staphylococcus aureus.

The mitogenic activity of protein A (PA), leucoagglutinin (LA) and pokeweed mitogen (PWM) was tested in six cases of chronic lymphatic leukaemia (CLL), and the response to PA and LA in six healthy controls. The effect of foetal calf serum (FCS) and pooled human AB serum in the cultures was tested in two patients. The response to LA in the patients was about one tenth of that in the controls. The response to PA was strong both in patients and in healthy controls. However, in lymphocytes from CLL patients this response was serum-dependent, being very strong with FCS in the culture medium, but absent when the medium contained human AB serum. Lymphocytes from normal controls responded to PA in the presence of AB serum.