KLRK1 and hydrops fetalis: In detail, the loss of the HF-IP site is due to local increased interferon-γ (INF-γ) production, cytokines such as IL-15, IL-2, and CXCL2, upregulation of NKG2D ligands (e.g., MICA and ULBP3/6), and MHC I and MHC II molecules, in addition to the decrease of the IP guardians such as transforming growth factor-β1 (TGF-β1) and interleukin-10 (IL-10), [10,11,12].