Lymph node accessory cells in the immune response. The primary response to paratyphoid vaccine in rat parathymic lymph nodes.

The immune response in the rat parathymic lymph node was studied after administration of antigen into the peritoneal cavity. Special attention was paid to the accessory cells, which might induce the response. During the induction phase of the response a heterogeneous population of non-lymphoid mononuclear cells was present in the subcapsular sinus and the cortex of the node. These cells resemble "veiled cells" described in skin draining lymph and interdigitating cells in the paracortex of skin draining lymph nodes, but they do not contain Birbeck granules. It is concluded that the appearance of these granules depends on the site of the exudate provocation and that the presence of the organelles in these accessory cells is not obligatory for lymphocyte stimulation.