Generation of mucosal mast cells is stimulated in vitro by factors derived from T cells of helminth-infected rats.

The connective tissue of rats, and several other species of mammals, contains two distinct types of mast cells that differ in morphology, histochemical staining properties and location1. One type, frequently called the normal connective tissue mast cell, can be obtained in nearly homogeneous preparation from a mixed cell population in the peritoneal cavity and forms the basis of our knowledge of mast cells. The other type is referred to as the mucosal mast cell because in normal rats it has been observed only in mucosal tissue. Infection with helminth parasites induces an exteNsive accumulation of mast cells and eosinophils in the tissues, and parasites of mucous surfaces, in particular, stimulate a rapid hyperplasia of mucosal mast cells. However, the origin of mucosal mast cells, and their relationship to the connective tissue mast cells is uncertain. We now slow that lymphocytes of helminth-infected rats, on in vitro stimulation with specific antigen, release factors causing pronounced mucosal mastocytosis in normal rat bone marrow cultures.