NOVEL CD32 ISOFORMS MODULATE NK CELL FUNCTIONS

人类自然杀伤（NK）细胞能够自发杀死某些肿瘤和病毒感染的细胞。 此外，NK细胞可以通过抗体依赖性细胞毒性（ADCC）杀死IgG抗体包被的靶细胞，并且正是IgG的Fc部分与NK细胞表面上的Fc受体（Fc γ R）结合，为裂解机制的激活提供信号。 几乎所有NK细胞都表达Fc γ RIII，并且该受体已显示参与NK细胞介导的ADCC。 直到最近，这被认为是NK细胞上表达的唯一Fc γ R。 然而，我们最近发现，某些个体的NK细胞也表达高水平的Fc γ RII，并发现这些是Fc γ RIIC基因的产物，这是一种在任何细胞中都没有得到很好表征的同种型。 我们进一步表明，在第一胞外（EC 1）域的等位基因多态性aa 13的结果在个人的NK细胞是CD 32阴性或CD 32阳性。 当在NK细胞上表达时，该分子可以触发ADCC并增加细胞内CA+2通量。 此外，使用两种Fc γ RIIc亚型转染的Jurkat细胞，我们已经确定了这些Fc γ R的配体结合特异性和信号转导途径。 这些研究具有潜在意义，因为NK细胞先前未显示表达CD 32，因此这可能代表激活和/或调节NK细胞裂解的新手段。 基于这些数据，我们假设某些个体NK细胞上高水平Fc γ RII表达的存在通过激活和/或调节NK细胞的溶解和免疫调节功能影响其NK细胞的功能。 本提案旨在确定由人NK细胞表达的新型CD 32亚型的功能意义，并通过评估其在NK细胞功能中的作用来验证我们的假设。该提案的具体目的是：1）确定新的CD 32亚型在正常NK细胞中的功能意义; 2。确定MHC I类特异性抑制性受体在CD 32介导的功能调节中的作用; 3）评估CD 32 pos或CD 32 neg个体的NK细胞针对肿瘤靶点的ADCC活性的可能差异。

Human natural killer (NK) cells are capable of spontaneously killing certain tumor and virus-infected cells. In addition, NK cells can kill IgG antibody-coated target cells via antibody- dependent cellular cytotoxicity (ADCC) and it is the Fc portion of the IgG binding to an Fc receptor (FcgammaR) on the surface of the NK cell that provides the signal for the activation of the lytic machinery. Almost all NK cells express FcgammaRIII, and this receptor has been shown to be involved in NK cell-mediated ADCC. Until recently this was thought to be the only FcgammaR expressed on NK cells. However, we have recently shown that NK cells, from certain individuals, also express high levels of FcgammaRII, and found these to be products of the FcgammaRIIC gene, an isoform that has not been well characterized in any cell. We have further shown that an allelic polymorphism of aa 13 in the first extracellular (EC1) domain results in individuals whose NK cells are CD32neg or CD32pos. This molecule, when expressed on NK cells, can trigger ADCC and increases in intracellular CA+2 flux. In addition, using Jurkat cells transfected with two FcgammaRIIc isoforms we have defined the ligand binding specificity and signal transduction pathway of these FcgammaRs. These studies are of potential significance because NK cells have not been previously shown to express CD32 and thus this potentially represents a new means of activating and/or regulating NK cell lysis. Based on these data we hypothesize that the presence of high levels of FcgammaRII expression on NK cells of some individuals influences the function of their NK cells by activating and/or regulating the lytic and immunoregulatory function of NK cells. The present proposal is aimed at determining the functional significance of the novel CD32 isoforms expressed by human NK cells and to test our hypothesis, by assessing their role in NK cell functions. The specific aims of the proposal are: 1) To determine the functional significance of novel CD32 isoforms in normal NK cells; 2. To determine the role of MHC class I-specific inhibitory receptors in the modulation of functions mediated by CD32; 3) To assess the possible differences in ADCC activity of NK cells against tumor targets from CD32pos or CD32neg individuals.