CD160 is an Ig-like activating NK cell receptor expressed on the majority of circulating NK cells. This population corresponds to the nonproliferating, highly cytolytic, CD56dimCD16+ subset. CD160 engagement by HLA-C molecules mediates cytotoxic function. In this study, we report that upon specific activation by the physiological ligand HLA-C, or Ab cross-linking, CD160+ peripheral blood NK cells produce IFN-γ, TNF-α, and IL-6. This unique CD160-mediated cytokine production differs from the one observed after CD16 engagement whose expression is also restricted to the CD56dim cytotoxic NK cell subset. As already reported for the CD160-mediated cytotoxic effector function, CD160-mediated cytokine production by peripheral blood-NK cells is negatively controlled by the killer Ig-like receptor CD158b. Thus, the CD160 receptor represents a unique triggering surface molecule expressed by cytotoxic NK cells that participates in the inflammatory response and determines the type of subsequent specific immunity.

PIBF was previously identified as a 34 kDa immunomodulatory molecule secreted by pregnancy lymphocytes and is thought to play a crucial role in preventing rejection of the embryo by the maternal immune response. Recent data suggested that PIBF protein was also expressed by the progesterone receptor (PR) positive MCF-7 breast tumor cell line. Given the notion that a number of proteins shown to be involved in tumorigenesis are associated with the centrosome and disturbed centrosome function causes unequal segregation of chromosomes, studies to evaluate whether or not PIBF that is highly expressed in tumors is directly involved in tumorigenesis are thus warranted.

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Progesterone-induced blocking factor is produced by pregnancy lymphocytes and also by malignant tumors. The PIBF-induced Th2-dominant immune response is favorable during pregnancy but might facilitate tumor growth by suppressing local antitumor immune responses.