Differences in Localization of Salmonella Flagella in Lymph Node Follicles of Germ-free and Conventional Rats

Abstract

STUDIES on the induction of antibody production have shown that subcutaneously injected immunogens can be processed in two ways by draining lymph nodes¹. Most of the immunogen retained in the node is actively phagocytosed by the macrophages of the sinuses of the medulla, while a smaller portion becomes attached to the surfaces of dendritic cellular processes iri the primary follicles of the cortex^1–5. This latter phenomenon seems to be important because germinal centres subsequently form in immediate relation to this surface-retained immunogen^1–5. Because the ability of follicular cells to capture immunogens is decreased in tolerant animals and increased in actively or passively immunized animals^6–8, it may be that opsonins, specific or non-specific, are required for follicular localization of immunogens and thus for the formation of germinal centres in lymph nodes. To test this hypothesis further we have compared the degree of follicular localization of flagella of Salmonella adelaide labelled with iodine-125 in germ-free rats and in conventionally raised rats, assuming that germ-free rats would have experienced less exposure to antigens which might have induced cross-reacting or non-specific opsonins.