Fleit H B, Kobasiuk C D
Department of Pathology, State University of New York, Stony Brook 11794-8691.
J Leukoc Biol. 1991 Jun;49(6):556-65. doi: 10.1002/jlb.49.6.556.
THP-1 cells are a monocyte-like cell line derived from a patient with acute monocytic leukemia and unlike other leukemic cell lines has a normal diploid karyotype. We have characterized Fc gamma R expression on this cell line by flow cytometry, radiolabeled IgG1 and monoclonal antibody (mAb) binding assays, and biochemical analysis. Flow cytometric analysis of THP-1 cells with anti-Fc gamma RI, II, and III mAb, and a rabbit anti-Fc gamma RIII F(ab')2 demonstrated that only Fc gamma RI and Fc gamma RII are expressed by these cells. A panel of anti-Fc gamma RIII mAb (anti-CD16) failed to bind to THP-1 cells. Biochemical studies identified polypeptides of 64 to 78 kDa (Fc gamma RI) and of 42 to 53 kDa (Fc gamma RII). Fc gamma R expression was determined by binding of radioiodinated human IgG1 (to detect Fc gamma RI), mAb IV.3 (to detect Fc gamma RII), or rabbit IgG immune complexes. Thirty-five thousand high affinity binding sites (dissociation constant [KD] = 4.22 x 10(-9) M) for IgG1 were found on THP-1 cells. Interferon-gamma (IFN gamma) upregulated Fc gamma RI expression by THP-1 cells 2.8-fold, whereas Fc gamma RI on U937 cells was increased six- to eight-fold by this cytokine. Phorbol myristate acetate (PMA), tumor necrosis factor-alpha (TNF alpha), and vitamin D3 had no effect on IgG1 binding by THP-1 cells. Fifty thousand IgG molecules in immune complexes bound to THP-1 cells. IFN gamma treatment increased this binding by four-fold, PMA treatment resulted in a 50% increase in the number of IgG immune complexes bound, whereas vitamin D3 treated THP-1 cells bound half as many IgG immune complexes as control cells. Binding assays utilizing mAb IV.3 identified 50,000 sites per cell. Treatment of THP-1 cells with IFN gamma, TNF alpha, PMA, or vitamin D3 had no effect on Fc gamma RII expression. That Fc gamma RI plays a predominant role in immune complex binding was demonstrated by inhibition studies. Human IgG1 as well as mouse IgG2a mAb to Fc gamma RII inhibited immune complex binding by 76 to 84%, whereas mouse IgG1 mAb to Fc gamma RII had minimal effect on immune complex binding. Fc gamma R expression may not be linked to differentiation of THP-1 cells since only 1,25 vitamin D3 was able to induce the expression of CD14, a marker of mature monocytic phenotype.
THP-1细胞是一种源自急性单核细胞白血病患者的单核细胞样细胞系，与其他白血病细胞系不同，它具有正常的二倍体核型。我们通过流式细胞术、放射性标记的IgG1和单克隆抗体（mAb）结合试验以及生化分析，对该细胞系上FcγR的表达进行了表征。用抗FcγRI、II和III mAb以及兔抗FcγRIII F(ab')2对THP-1细胞进行流式细胞术分析表明，这些细胞仅表达FcγRI和FcγRII。一组抗FcγRIII mAb（抗CD16）未能与THP-1细胞结合。生化研究鉴定出64至78 kDa（FcγRI）和42至53 kDa（FcγRII）的多肽。通过放射性碘化人IgG1的结合（以检测FcγRI）、mAb IV.3（以检测FcγRII）或兔IgG免疫复合物来测定FcγR的表达。在THP-1细胞上发现了35000个IgG1的高亲和力结合位点（解离常数[KD]=4.22×10(-9)M）。干扰素-γ（IFNγ）使THP-1细胞的FcγRI表达上调2.8倍，而该细胞因子使U937细胞上的FcγRI增加6至8倍。佛波醇肉豆蔻酸酯乙酸酯（PMA）、肿瘤坏死因子-α（TNFα）和维生素D3对THP-1细胞与IgG1的结合没有影响。免疫复合物中的50000个IgG分子与THP-1细胞结合。IFNγ处理使这种结合增加了4倍，PMA处理使结合的IgG免疫复合物数量增加了50%，而维生素D3处理的THP-1细胞结合的IgG免疫复合物数量仅为对照细胞的一半。利用mAb IV.3的结合试验确定每个细胞有50000个位点。用IFNγ、TNFα、PMA或维生素D3处理THP-1细胞对FcγRII的表达没有影响。抑制研究表明FcγRI在免疫复合物结合中起主要作用。人IgG1以及抗FcγRII的小鼠IgG2a mAb可使免疫复合物结合减少76%至84%，而抗FcγRII的小鼠IgG1 mAb对免疫复合物结合的影响最小。FcγR的表达可能与THP-1细胞的分化无关，因为只有1,25-维生素D3能够诱导成熟单核细胞表型标志物CD14的表达。
