Lymphocyte trapping and activation in the regional lymph node stimulated by cellular and soluble antigens.

: Cellularity and intensity of RNA synthesis in the popliteal lymph nodes of mice treated with different types of antigen injected subcutaneously into the hind footpads were followed. The percentage of lymphocytes with nucleoli synthesizing the RNA, incorporation of 3H-uridine and cellularity increased in the lymph node draining the site of antigenic stimulation. This activation occurred as early as 1 day after injection of living cells and the time of maximal RNA synthesis preceded the time of maximal cellularity. The response was seen as late as 3-7 days after injection of dead cells and soluble antigens. In contrast to living cells, soluble antigens induced the trapping of cells before the increase of the formation of ribonucleic acid. The described testing of stimulation of the draining lymph node may serve as a rapid, and economical assay for immunogenicity of unknown substances.