Thymic medullary lymphocytes: I. Lymphokines produced by thymic medullary lymphocytes as a second signal for intrathymic stem cell homing

Abstract

Lymphokines produced by thymic medullary cells (TMC) or by normal spleen cells after allogeneic stimulation have been tested for their chemotactic properties in an in vitro migration test. Lymphokines produced by TMC specifically attract cells from nude spleen or from T-cell-deprived spleen depleted of macrophagic cells, but not from normal adult spleen. Supernatants produced by normal adult spleen cells did not attract any of the cells tested (nude spleen cells, T-cell-deprived spleen cells, or normal spleen cells). These results suggest a role for mature TMC in intrathymic stem cell homing. These cells could deliver a second signal to the stem cell, complementary to those provided by thymic epithelium.