一个新的人B细胞活化抗原-5C5

5C5-a novel antigen restrictedly exprossed on human activated B cells

用活化人B细胞株3D5细胞免疫小鼠和作为筛选的靶细胞,我们建立了产生单克隆抗体5C5的杂交瘤细胞株。此单抗识别的抗原5C5在25μg/ml anti-μ刺激的B细胞,于第10小时开始表达,亦即于G_1期开始表达。5C5细胞百分率随培养时间而增多。在PWM诱导下.外周血单一核细胞中5C5^+细胞随培养时间而增加,至第3～4天达最高峰,然后减少,至第7天降至本底水平。5C5^+细胞在不能为BCDF诱导分化至免疫球蛋白分泌细胞(ISC)的B细胞株3D5,Raji和Daudi阳性,但在能为BCDF诱导分化至ISC的CESS和SKW6细胞却不表达。这均表明5C5抗原表达于B细胞活化的早期和中期,但在B细胞终末分化阶段消失。在休止期B细胞、休止期T细胞、PHA激活的T细胞、单核细胞和中性粒细胞,以及在所检测的T细胞株和髓细胞株,5C5抗原均为阴性。^(125)I标记后用单抗5C5免疫沉淀提取的抗原,在还原与非还原条件下电泳,均只有分子量为52000的一条带,表明5C5是一个单链细胞表面蛋白。鉴于5C5抗原的分子量与文献中已报道的B细胞活化抗原分子量不同,以及5C5在细胞株表达的特点,它可能是一个新的人B细胞活化抗原。

Using a human activated B cell line 3D5 in immunization of mouse and as targets in screening, a hybridoma producing McAb 5C5 has been established. The antigen recognized by the McAb starts its expression on low dose anti-μ-activated B cells at their G_1 phase at the 10th hour. The number of 5C5^+ cells increases with time. At the stimulation of PWM, the number of 5C5^+ cells in PBMNC also increases with time, and peaks on day 3 to 4, then docreases and comes to the background on day 7.5C5 antigen is positive on the B cell lines which can not be induced to differentiate to Ig-secre-ting cells (ISC), but negative on those being able to be driven to differentiate to ISC by BCDF. All the data indicate that 5C5 expresses at the early and mid stages, but disappears at the terminal stage of B cell activation and differentiation. 5C5 antigen does not expresses on resting B cells, resting T cells, PHA-activated T cells, monocytes, neutrophils, and the T cell and myeloid cell lines detected. Electrophoresis under both the nonreducing and reducing state for the ^(125)I-label led antigen immunoprecipi tated with McAb 5C5 shows a single band with a molecular weight of 52000, suggesting that 5C5 be a single chain cell surface protein. Since the MW of 5C5 is different from that of those B cell activation antigens reported in literature, and since ins specific expression on cell lines, 5C5 antigen might be a novel B eel I-restricted activation antigen.