Characterization of guinea pig mitogenic factor.

Guinea pig mitogenic factor (M.F.) was identified in antigen-stimulated guinea pig lymph node lymphocyte cultures by the ability of supernatants to stimulate DNA synthesis in non-immune lymphocytes. Its activity is not augmented by the presence of antigen and it will stimulate lymphocytes made unresponsive to the eliciting antigen. M.F. production by lymphocytes is detectable within 6 hr after antigen stimulation and reaches a maximum at 24 hr. DNA synthesis produced by M.F. is maximal at 48 hr. M.F. is heat stable at 60 degrees C. Its molecular weight is in the range of 20,000 to 30,000 daltons. M.F. activity appears to be relatively resistant to the action of proteolytic enzymes.