Histological modifications of the lymph nodes in mice bearing syngeneic grafts of tumours induced by methylcholanthrene.

Light and electron microscopical studies demonstrate that regional but also non-regional lymph nodes of C57BL mice grafted by tumours, induced by methylcholanthrene, are able to elicit a complex immunological response of the cellular, as well as of the humoral types. No significant difference was found according to the growth rate and the immunogenicity of the six tumours investigated. The cellular immunization is predominant during the two first weeks. It is mainly characterized by the appearance in the paracortical area of numerous immunoblasts which are in close connexions with'dendritic' macrophages showing multiple long cytoplasmic expansions. During the same period of time, the reticulum cells become hyperplasic in the sinus. From the 15th day to the death of the animals, the cellular immunizaiton progressively regresses while a humoral immunity develops. It shows itself as an hypertrophy of the lymph follicles and an increase in the number of medullary cord plasma cells.