Gastroenterology Division, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States.
Rheumatology Division, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States.
Front Immunol. 2019 Jul 23;10:1692. doi: 10.3389/fimmu.2019.01692. eCollection 2019.
Natural killer (NK) cells play an important role in the innate immune response. The summation of activation and inhibitory signals delivered through cell surface membrane receptors determines NK cell function. However, the continuous engagement of an activating receptor on NK cells appears to render the cells hyporesponsive to stimulation through other unrelated activating receptors. The mechanism by which this takes place remains unclear. Herein we demonstrate that continuous engagement of the Ly49H receptor with its ligand, m157, results in Ly49H NK cells that are hyporesponsive to further stimulation by other ITAM-dependent and independent receptors, while Ly49H NK cells remain unaffected. The hyporesponsiveness of the NK cell correlates with the degree of Ly49H receptor downmodulation on its cell surface. We observe defects in calcium flux in the hyporesponsive NK cells following stimulation through the NK1.1 receptor. In addition, we observe differences in signaling molecules that play a role in calcium flux, including spleen tyrosine kinase (Syk) at baseline and phosphorylated phospholipase C gamma 2 (p-PLCγ2) at both baseline and following stimulation through NK1.1. We also demonstrate that various ITAM associated activation receptors, including Ly49H, remain associated with their respective adaptor molecules. With regard to NK cell function, we did not find differences in the formation of metastatic lung lesions following IV injection of B16 melanoma cells. However, we did observe defects in rejection of missing-self targets . The data suggest that continuous engagement of the Ly49H activating receptor on NK cells results in hyporesponsiveness of the NK cells to all of the ITAM-dependent and independent receptors we analyzed due to altered signaling pathways downstream of the receptor and adaptor molecule.
自然杀伤 (NK) 细胞在先天免疫反应中发挥重要作用。通过细胞表面膜受体传递的激活和抑制信号的总和决定了 NK 细胞的功能。然而，NK 细胞上持续的激活受体的结合似乎使细胞对其他不相关的激活受体的刺激反应迟钝。这种情况发生的机制尚不清楚。在此，我们证明 Ly49H 受体与其配体 m157 的持续结合导致 Ly49H NK 细胞对其他 ITAM 依赖性和非依赖性受体的进一步刺激反应迟钝，而 Ly49H NK 细胞不受影响。NK 细胞的低反应性与细胞表面 Ly49H 受体的下调程度相关。我们观察到在通过 NK1.1 受体刺激后，低反应性 NK 细胞中的钙通量出现缺陷。此外，我们观察到在钙通量中发挥作用的信号分子存在差异，包括基础状态下的脾酪氨酸激酶 (Syk) 和 NK1.1 刺激后基础状态和磷酸化磷脂酶 Cγ2 (p-PLCγ2)。我们还证明了各种 ITAM 相关的激活受体，包括 Ly49H，仍然与其各自的衔接分子相关联。关于 NK 细胞功能，我们没有发现 IV 注射 B16 黑色素瘤细胞后转移性肺病变形成的差异。然而，我们确实观察到对缺失自我靶标的排斥缺陷。数据表明，由于受体和衔接分子下游信号通路的改变，NK 细胞上持续的 Ly49H 激活受体的结合导致 NK 细胞对我们分析的所有 ITAM 依赖性和非依赖性受体的反应迟钝。
