Morphologic Changes in Draining Lymph Nodes and in Lymphocyte Cultures after Sensitization with Complete or Incomplete Freund's Adjuvant. Correlation with Immunologic Events in Vivo and in Culture

Abstract

Abstract Morphologic changes occurring in draining lymph nodes were studied at two intervals after sensitization of guinea pigs with human serum albumin (HSA) in complete or incomplete Freund's adjuvant (CFA or IFA) and were correlated with the immunologic response of these animals. At 1 week after sensitization with HSA in IFA guinea pigs were primed for the delayed-onset reactions of cutaneous basophil hypersensitivity (CBH) but had little circulating antibody. Their lymph nodes manifested paracortical cell hyperplasia with a striking degree of blast transformation, and cells from such nodes, cultured in the presence of antigen, incorporated 3H-thymidine at an enhanced rate and underwent morphologic blast transformation. At 6 weeks, these animals had lost CBH skin reactivity but had high titers of circulating antibody. Draining lymph nodes contained prominent germinal centers and numerous plasma cells, but paracortical blasts had returned to control levels, and isolated cells were not stimulated to incorporate thymidine by antigen in culture. By contrast, animals sensitized with the same antigen in CFA developed progressively indurated skin reactions characteristic of delayed hypersensitivity (DH), as well as high titers of circulating antibody. In draining lymph nodes, blast cells outside of germinal centers were never as numerous as at 1 week following administration of antigen in IFA; however, a significant number persisted at 6 weeks when excellent antigen-induced thymidine incorporation and blast transformation could be achieved in culture. Taken together, these data provide additional evidence for the existence of two distinguishable forms of cellular immunity, DH and CBH, and define certain properties of each.