The Number of Reactive Cells in Mouse Lymphocyte Cultures Stimulated by Phytohemagglutinin, Concanavalin a or Histocompatibility Antigen

Abstract

Abstract Mouse lymphocytes were cultured with phytohemagglutinin, concanavalin A, or allogeneic cells. The number of cells entering DNA synthesis was determined by pulse labeling with tritiated thymidine at various times. Phytohemagglutinin induced 11 to 26% of the initial population to enter the proliferative cycle over 1 to 4 days. Concanavalin A induced 29 to 46% of the initial population to enter proliferation over 1 to 5 days. In mixed leukocyte cultures approximately 1% of BALB/c or CBA lymphocytes responded to F1 cells over 1 to 5 days and in two-way mixed cultures between BALB/c and CBA cells a similar proportion, 1% of the initial population, responded. Variations in the total cell concentration or the ratio of parental to F1 cells in mixed leukocyte cultures produced no change in the percentage of reactive cells. The number of reactive cells was increased approximately 7-fold, nearly 8% of the initial population, in BALB/c mice that had been pre-sensitized with F1 cells. These findings are discussed in relation to the recognition of antigen by thymus derived lymphocytes.