Khattri R, Hansen B, Nichols T C, Palmer K L, Gilman-Sachs A, Baum L L
Department of Microbiology and Immunology, University of Health Sciences/The Chicago Medical School, Illinois 60064.
Cell Immunol. 1994 May;155(2):457-75. doi: 10.1006/cimm.1994.1138.
C-reactive protein (CRP), an acute phase protein in human serum, is present on large granular lymphocytes (LGL). Anti-CRP inhibits natural killer (NK) cell-mediated lysis. Our current study shows that anti-CRP also inhibits antibody-dependent cell-mediated cytotoxicity (ADCC) of LGL. Calcium influx and protein kinase C (PKC) activation are the early signal transduction events in NK activation. In the conjugates formed between LGL and targets (NK or ADCC), 75-90% of LGL respond with a calcium influx. Addition of anti-CRP had no effect on the percentage of LGL which respond to target cell binding or on the magnitude of the calcium response of LGL. This was true for both NK and ADCC effector cells. Crosslinking anti-CRP with a secondary antibody did not alter this result. Next, the effect of PMA, a PKC activator, and calcium ionophore, A23187, on anti-CRP-mediated inhibition of cytotoxicity were studied. PMA alone reversed most of the inhibition of lysis seen with anti-CRP. Based on previous observations that anti-CRP inhibited target cell-stimulated release of lytic factors, the effect of anti-CRP on release of lytic factors stimulated by PMA and calcium ionophore was evaluated. Anti-CRP blocked the release of lytic factors stimulated by PMA and ionophore. Release of lytic factors involves the rearrangement of cytoskeletal element of NK cell toward the target cell. The effect of anti-CRP on cytoskeletal reorganization was studied. In conjugates formed between effector and target cells, the polarization of cytoskeleton at the contact site of NK and target cell was significantly reduced in the presence of anti-CRP. Although anti-CRP inhibits both ADCC and NK lytic mechanisms, it does not alter target cell-induced Ca2+ influx. CRP interacts with the secretory mechanisms involved in granule exocytosis since anti-CRP inhibits the cytoskeletal polarization and the release of lytic factors and PMA might reverse anti-CRP-mediated inhibition by activating alternative mechanisms of cytotoxicity in effectors.
C反应蛋白（CRP）是人体血清中的一种急性期蛋白，存在于大颗粒淋巴细胞（LGL）上。抗CRP可抑制自然杀伤（NK）细胞介导的细胞溶解作用。我们目前的研究表明，抗CRP还可抑制LGL的抗体依赖性细胞介导的细胞毒性（ADCC）。钙内流和蛋白激酶C（PKC）激活是NK激活过程中的早期信号转导事件。在LGL与靶细胞（NK或ADCC）形成的结合物中，75%至90%的LGL会出现钙内流反应。添加抗CRP对响应靶细胞结合的LGL百分比或LGL的钙反应幅度没有影响。对于NK和ADCC效应细胞均如此。用二抗交联抗CRP并不会改变这一结果。接下来，研究了PKC激活剂佛波酯（PMA）和钙离子载体A23187对抗CRP介导的细胞毒性抑制作用的影响。单独使用PMA可逆转抗CRP所见的大部分溶解抑制作用。基于先前的观察结果，即抗CRP抑制靶细胞刺激的溶解因子释放，评估了抗CRP对PMA和钙离子载体刺激的溶解因子释放的影响。抗CRP阻断了PMA和离子载体刺激的溶解因子释放。溶解因子的释放涉及NK细胞细胞骨架元件向靶细胞的重排。研究了抗CRP对细胞骨架重排的影响。在效应细胞与靶细胞形成的结合物中，在存在抗CRP的情况下，NK与靶细胞接触部位的细胞骨架极化明显降低。尽管抗CRP同时抑制ADCC和NK溶解机制，但它不会改变靶细胞诱导的Ca2+内流。CRP与颗粒胞吐作用所涉及的分泌机制相互作用，因为抗CRP抑制细胞骨架极化和溶解因子释放，而PMA可能通过激活效应细胞中的替代细胞毒性机制来逆转抗CRP介导的抑制作用。
