Immunoprecipitation and radioimmunological studies of a lymph node activating factor released during contact of H-2-or HLA-different lymphocytes.

Immunoprecipitation studies showed that the supernatants from the 4-hour mixed cultures of allogeneic mouse lymphoid cells contained a specific component with the alpha2-globulin electrophoretic mobility which can correspond to, or to which a "lymph node activating factor" can be bound. In addition, during allogeneic cell culture serum proteins with the prealbumin mobility were released into the culture medium and in the control culture of cells from only one donor proteins with the albumin mobility predominated. In the supernatants from the 4-hour cultures of human HLA-identical and HLA-diferent lymphocytes beta2-microglobulin was determined by immunodiffusion and radioimmunologically.