The cellular basis of immunological recovery in nude mice after thymus grafting.

The changes that take place in the peripheral lymphoid tissues of congenitally athymic nude mice after stimulation with polysaccharide and after thymus grafting are described. We have found that after antigen stimulation there is an increase in the cellularity of the primary nodules and changes in the endothelial wall of the post-capillary venules suggestive of an increased cell traffic into the lymph nodes. No germinal centres were observed in nude mice subjected or not to deliberate antigen stimulation. After thymus grafting a slow infilling of the thymus-dependent areas by lymphocytes took place, in addition, the presence of germinal centres was noticed. A number of possible explanations for the findings described is put forward and discussed.