A novel MyD-1 (SIRP-1alpha) signaling pathway that inhibits LPS-induced TNFalpha production by monocytes.

MyD-1 (CD172) is a member of the family of signal regulatory phosphatase (SIRP) binding proteins, which is expressed on human CD14+ monocytes and dendritic cells. We now show a novel role for MyD-1 in the regulation of the innate immune system by pathogen products such as lipopolysaccharide (LPS), purified protein derivative (PPD), and Zymosan. Specifically, we demonstrate that ligation of MyD-1 on peripheral blood mononuclear cells (PBMCs) inhibits tumor necrosis factor alpha (TNFalpha) secretion but has no effect on other cytokines induced in response to each of these products.