Cellular localization of 125I-labelled Salmonella adelaide flagellin following injection into the rat in the presence of Freund's complete adjuvant.

Abstract

SummaryA comparison has been made of the uptake of 125I‐labelled flagellin in the pepliteal lymph nodes following its injection into the foot‐pad of the rat in aqueous solution and in Freund's complete adjuvantIn aqueous solution the cellular localization of the antigen within the node was found to follow the characteristic pattern previously described by Ada, Nossal and Austin (1964) with high concentrations of label appearing in the medullary macrophages and over the lymphoid follicles of the cortex.Antigen injected in adjuvant persisted for a long period both at the injection site and in the draining lymph node. Only minimal follicular localization of the antigen was observed within the node. Instead large amounts of label were found to accumulate in the subcapsular sinus and from this source, relatively small aggregates of label associated with droplets of lipid from the adjuvant appeared to migrate slowly and randomly into the body of the node. This process was accompanied by lymph node hyperplasia associated principally with a massive plasma Cell proliferation in the medullary area. At the same time high titres of circulating antibody developed.It has been postulated that antigen taken up by the reticular dendritic web of the cortical lymphoid follicles, following its injection in aqueous solution, may act as an antigen depot with which antigen‐sensitive precursors of antibody‐ producing cells may make contact and receive their specific inductive stimulus. It is further suggested that, when antigen is Injected in Freund's complete adjuvant, not only does the adjuvant stimulate intensive lymphoid cell proliferation within the draining lymph nodes with a probable increase in the number of antibody‐producing cell precursors, but that the antigen in the antigen‐ adjuvant droplets which reach the interior of the node, both in quantity and persistence, may fulfil more efficiently the role played by antigen on the reticulum cells of the cortical follicles.