Stein R, Belisle E, Hansen H J, Goldenberg D M
Garden State Cancer Center, Center for Molecular Medicine and Immunology, Newark, NJ 07103.
Cancer Immunol Immunother. 1993 Oct;37(5):293-8. doi: 10.1007/BF01518451.
LL2 is a murine monoclonal antibody IgG2a reactive with B cells and non-Hodgkin's B-cell lymphoma, which, in a radioiodinated form, induces responses in lymphoma patients [Goldenberg et al. (1991) J Clin Oncol 9:548-564]. In this report we identify LL2 as a member of the CD22 cluster. The molecular size of the antigen, its expression profile, and competitive blocking studies were used to establish this identification. By Western blot analysis and immunoprecipitation studies using the Raji Burkitt's lymphoma cell line metabolically labelled with [3H]leucine, the LL2 antigen was determined to correspond to a molecular mass of 140 kDa. The molecular mass of the LL2 antigen, and the B-cell-restricted reactivity of the LL2 antibody, were consistent with both the CD21 and CD22 clusters. To assess additional similarities and differences between LL2 and anti-CD22 and anti-CD21, the binding of these mAb to cultured cell lines, Nalm-6 and Molt-4, was compared by flow cytometry. The binding profile of LL2 on these cell lines was consistent with anti-CD22, but not anti-CD21. Sequential immunoprecipitation and cross-blocking studies with anti-CD22 monoclonal antibodies recognizing established CD22 epitopes were performed to confirm that LL2 reacts with CD22 and to determine which epitope LL2 recognizes. Binding of 131I-LL2 to Raji cells is inhibited over 90% by prior incubation of the target cells with unlabelled RFB4, indicating that LL2 belongs to the same epitope group as RFB4, i.e., epitope B.
LL2是一种与B细胞和非霍奇金B细胞淋巴瘤反应的鼠单克隆抗体IgG2a，其放射性碘化形式可诱导淋巴瘤患者产生反应[戈尔登伯格等人（1991年）《临床肿瘤学杂志》9:548 - 564]。在本报告中，我们确定LL2是CD22簇的成员。通过抗原的分子大小、其表达谱以及竞争性阻断研究来确定这一身份。利用用[3H]亮氨酸进行代谢标记的拉吉伯基特淋巴瘤细胞系，通过蛋白质印迹分析和免疫沉淀研究，确定LL2抗原的分子量对应于140 kDa。LL2抗原的分子量以及LL2抗体的B细胞限制性反应性与CD21和CD22簇均相符。为了评估LL2与抗CD22和抗CD21之间的其他异同，通过流式细胞术比较了这些单克隆抗体与培养细胞系Nalm - 6和Molt - 4的结合情况。LL2在这些细胞系上的结合谱与抗CD22一致，但与抗CD21不一致。进行了与识别既定CD22表位的抗CD22单克隆抗体的顺序免疫沉淀和交叉阻断研究，以确认LL2与CD22反应并确定LL2识别哪个表位。用未标记的RFB4预先孵育靶细胞，可使131I - LL2与拉吉细胞的结合受到90%以上的抑制，表明LL2与RFB4属于同一表位组，即表位B。
