Natural killer 1.1(+) T cells and "natural suppressor" T cells in the bone marrow.

Abstract

Unusual cells in the bone marrow of mice and/or humans suppress immune responses and inhibit the mixed leukocyte reaction, graft-versus-host disease, and systemic autoimmunity. Previous studies showed that these "natural suppressor" T cells expressed the CD4(-)CD8(-) T-cell receptor-alphabeta(+) phenotype. More recent studies demonstrate that the latter cells express the natural killer 1.1 (NK1.1) marker and are members of the NK1.1(+) T-cell family that secrete high levels of IFN-gamma and IL-4 after initial activation. The suppressive activity of the bone marrow NK1.1(+) T cells is dependent on their rapid secretion of high levels of IL-4. This unique cytokine secretion is not observed in conventional NK1. 1(-) T cells and can downregulate the function of the latter cells.