Ly49 receptors activate angiogenic mouse DBA+ uterine natural killer cells

Abstract

In humans, specific patterns of killer immunoglobulin-like receptors (KIRs) expressed by uterine natural killer (uNK) cells are linked through HLA-C with pregnancy complications (infertility, recurrent spontaneous abortion, intrauterine growth restriction and preeclampsia). To identify mechanisms underpinning the associations between NK cell activation and pregnancy success, pregnancies were studied in mice with genetic knockdown (KD) of the MHC-activated Ly49 receptor gene family. B6.Ly49 KD pregnancies were compared to normal control B6.Ly49 129 and C57BL/6 (B6) pregnancies. At mid-pregnancy (gestation day (gd9.5)), overall uNK cell (TCRb 2 CD122 1 DBA 1 DX5 2 (DBA 1 DX5 2 )) and TCRb 2 CD122 1 DBA 2 DX5 1 (DBA 2 DX5 1 )) frequencies in pregnant uterus were similar between genotypes. Ly49 KD lowered the normal frequencies of Ly49 1 uNK cells from 90.3% to 47.8% in DBA 2 DX5 1 and 78.8% to 6.3% in DBA 1 DX5 2 uNK cell subtypes. B6.Ly49 KD matings frequently resulted in expanded blastocysts that did not implant (subfertility). B6.Ly49 KD mice that established pregnancy had gestational lengths and litter sizes similar to controls. B6.Ly49 KD neonates, however, were heavier than controls. B6.Ly49 KD implantation sites lagged in early (gd6.5) decidual angiogenesis and were deficient in mid-pregnancy (gd10.5) spiral arterial remodelling. Ultrastructural analyses revealed that B6.Ly49 KD uNK cells had impaired granulogenesis, while immunocytochemistry revealed deficient vascular endothelial cell growth factor (VEGFA) production. Perforin and IFNG expression were normal in B6.Ly49 KD uNK cells. Thus, in normal mouse pregnancies, Ly49 receptor signaling must promote implantation, early decidual angiogenesis and mid-pregnancy vascular remodelling. Disturbances in these functions may underlie the reported genetic associations between human pregnancy complications and the inability of specific conceptus MHCs to engage activating KIR on uNK cells.

Leukocyte driven-decidual angiogenesis in early pregnancy

“…Pregnant females with pan Ly49 downregulation had deficient decidual angiogenesis at gd6.5 and decreased VEGFA expression by DBA 1 uNK cells at gd9.5-10.5. 134 These data suggest that the reported human gestational complications linked to conceptus genotypes unable to activate uNK cells maybe based upon inadequate uNK cell-driven angiogenesis.…”

“…44 Depletion or activation defects of DBA 1 uNK cells cause diminished VEGFA expression, reduced blood vessel density and reduced numbers of large sinuses. 26,88,132,133 In some of these mouse models, subfertility 134 and intrauterine growth restriction 26,133,134 are present. However, undefined compensatory mechanisms develop that successfully support these pregnancies to term.…”

“…Ly49 receptors are structurally distinct from but serve similar functions to human KIR in terms of regulating NK cell responses to MHC. 2,162 Mouse uNK cells express Ly49 receptors 36,134 and, in B6, two activating receptors: Ly49 D and H, and 4 inhibitory receptors: Ly49 A, C, I, G are present. 163 We addressed the importance of Ly49 receptors in the activation of uNK cell functions using a pan-Ly49 knockdown mouse model.…”

Reproductive Immunology Issue One: Cellular and Molecular Biology

“…13 Influences on leukocyte recruitment as well as on trophoblast invasion are discussed in normal as well as in pathological pregnancies. Lima and her colleagues 14 then report on the roles of the LY49 receptor gene family during mouse pregnancy, focusing on subsets of uterine natural killer (NK) cells. These authors found selective alterations of NK cell functions in pan LY49 gene knockdown mice.…”

Reproductive Immunology Issue 2: Cellular and Molecular Biology

“…[1][2][3] The dynamic changes in the uterine immune system induced over the course of a healthy pregnancy were also discussed. 2,[4][5][6][7] In Issue 2 of this special topic mini-series, the contributed papers are more clinically oriented and address current understanding of the immunological aspects of common pathologies that complicate human and livestock reproduction. Rodent models that provide key translational insights are blended with the clinical information.…”