Partial characterization of a factor present in normal human and animal serum which stimulate E rosette formation by lymphocytes from tuberculous patients.

The influence of sera from healthy human beings on ability of lymphocytes from patients with active pulmonary tuberculosis to form rosettes with SRBC was studied. Lymphocytes incubated for 2 hours with sera from healthy subjects recovered ability to form rosettes spontaneously with SRBC. The factor responsible for stimulation of the lymphocytes is contaned in the albumin fraction. Sera from mice, rabbits, guinea pigs and fetal calf serum had a similar effect to that of sera from healthy human beings. The character of this factor and the mechanism of its action are discussed. The stimulating factor is accompanied by an inhibitor.