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

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-alpha beta(+) 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.