Nature of the thymus dependency of mucosal mast cells. III. Mucosal mast cells in nude mice and nude rats, in B rats and in a child with the Di George syndrome.

Mucosal mast cells have been examined in the small intestinal mucosae of nude mice and nude rats, B rats and a child with the DiGeorge syndrome. In all three species, mast cells were present in normal numbers despite the athymic status of the nude mice and nude rats, the vestigial nature of the thymus in the child, and the functionally T lymphocyte-deprived status of the B rats. Connective tissue mast cells were also plentiful in skins and tongues of the nude mice and the child with thymic aplasia. It is concluded that normally neither population of mast cells has a obligatory dependence on the thymus or T lymphocytes for its differentiation, but that mucosal mast cells, under certain conditions of rapid hyperplasia, require an inductive influence provided by T lymphocytes.