Lymph node activation by a factor released from lymphocytes of normal mice in reaction with Mycobacterium kansasii.

Substances which have the same properties as the previously described lymph node activating factor are released from the 4-h culture of 10 X 10(6) lymph node cells from normal non-sensitized mice and 2.5--5 X 10(6) Mycobacterium kansasii cells. They increase the number of lymphocytes with nucleoli synthesizing ribonucleic acid in the popliteal lymph nodes of intact mice and give the precipitation lines with the beta- to alpha-globulin electrophoretic mobility, which are specific for the lymph node activating factor, in reaction with serum against the supernatants from mixed lymphocyte cultures. The conclusion drawn from these observations is that the release of the factor or related substances is one of the more general manifestations of the early response of lymphocytes to foreign cells. The activating and in immunoelectrophoresis specifically reacting substance is not released from lymphocytes of mice from a specific pathogen-free colony. We assume that the release of the factor is not the primary reaction of the non-sensitized lymphocytes but the secondary reaction of lymphocytes presensitized with substances which share antigenic determinants with Mycobacteria.