细胞因子介导的杀伤作用NK细胞能合成和分泌多种细胞因子如IFNγ天然杀伤细胞Natural killer cells NK cells是免疫系统的重要组成部分在机体抗病毒和抗肿瘤中发挥重要作用。可自发识别体内异常细胞并通过细胞毒性作用将其迅速清除同时产生各类促炎细胞因子和趋化因子招募和激活其他免疫细胞以启动适应性免疫反应。NK细胞表面具有IL-2中亲和性受体IL-2诱导NK的杀伤活性约需18-24

Cytotoxic Effects Mediated by Cytokines: NK cells are able to synthesize and secrete various cytokines, such as IFNγ. These cytokines play a crucial role in the immune response against viruses and tumors. NK cells can spontaneously recognize abnormal cells within the body and eliminate them through their cytotoxic effects. Additionally, NK cells produce inflammatory cytokines and chemokines, which recruit and activate other immune cells to initiate an adaptive immune response.

IL-2 Induction of NK Cell Activity: NK cells express IL-2 receptors on their surface, and the induction of NK cell cytotoxicity by IL-2 typically takes about 18-24 hours. The exact mechanism by which IL-2 induces NK cell activity is not fully understood, but it may involve increased expression of cell adhesion molecules, enhanced killing activity against target cells, increased granule formation in NK cell cytoplasm, and expression of serine esterase mRNA, which activate and enhance the cytotoxic effects of NK cells.

TGFβ Inhibition of NK Cell Function: TGFβ can inhibit NK cell function and promote their differentiation into ILC1 cells, which are tissue-resident cells with significantly reduced cytotoxicity against tumors. Inhibition of TGFβ in the tumor microenvironment is an important strategy to restore NK cell function and enhance their killing activity against tumors.

CD69: CD69 is an activation marker for NK cells. It forms a dimer and is expressed on activated T cells, B cells, NK cells, neutrophils, and platelets. CD69 belongs to the C-type lectin-like receptor family associated with natural killer cell activation antigens. It plays a critical role in NK cell function and helps maintain NK cell activation.

CD107a Expression: The basic principle of using flow cytometry to detect NK cell activity with CD107a marker is that NK cells contain numerous granules with cytolytic activity in their cytoplasm. Upon activation, NK cells release these granules into target cells through immune synapses. These granules contain cytolytic proteins, including perforin and granulysin, as well as lysosome-associated membrane protein 1 (LAMP1), also known as CD107a. CD107a is a marker for degranulation of NK cells. During NK cell killing of target cells, CD107a molecules are transported to the cell membrane, and the expression level of CD107a is significantly correlated with the cytotoxic activity of NK cells. Therefore, CD107a positive expression on NK cells represents NK cells with cytotoxic activity.

Granzyme B: Granzyme B is present in the granules of NK cells and cytotoxic T cells. It is crucial for the rapid induction of target cell death through apoptosis (interaction with cytotoxic T cells). Granzyme B activates a caspase cascade within the target cell, ultimately leading to cell death.

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