Some Factors Affecting the Secondary Immune Response in Tissue Cultures Containing Hydrocortisone

Summary A complete secondary immune response with antibody production is possible in a defined culture medium, if primed rabbit lymph node fragments are challenged with antigen in vitro and incubated with hydrocortisone. These studies confirm the observations of Ambrose (7, 8). Lymph node cell suspensions produced antibody only if prepared from tissue fragments which had been incubated in a hydrocortisone-containing medium for the preproduction phase (about 5 days). The hormone was not required for the antibody production phase of the cultures (tissue fragments or cell suspensions). Unrelated antigens showed no cross-immunogenicity, although phytohemagglutinin stimulated a slight nonspecific response. After priming injections in the feet, regional nodes were more responsive to challenge than were distant nodes. Spleen cultures were consistently negative under the conditions used. Tracer studies showed that antigen was taken up by primed tissue in vitro, bound firmly and released only when antibody appeared in the culture fluids.