Charite-Universitätsmedizin Berlin, CC12 Dept, Medicine/Rheumatology and Clinical Immunology, Chariteplatz 1, Berlin 10117, Germany.
Arthritis Res Ther. 2010;12(6):R204. doi: 10.1186/ar3179. Epub 2010 Nov 4.
Epratuzumab, a humanized anti-CD22 monoclonal antibody, is under investigation as a therapeutic antibody in non-Hodgkin's lymphoma and systemic lupus erythematosus (SLE), but its mechanism of action on B-cells remains elusive. Treatment of SLE patients with epratuzumab leads to a reduction of circulating CD27(negative) B-cells, although epratuzumab is weakly cytotoxic to B-cells in vitro. Therefore, potential effects of epratuzumab on adhesion molecule expression and the migration of B-cells have been evaluated.
Epratuzumab binding specificity and the surface expression of adhesion molecules (CD62L, β7 integrin and β1 integrin) after culture with epratuzumab was studied on B-cell subsets of SLE patients by flow cytometry. In addition, in vitro transwell migration assays were performed to analyze the effects of epratuzumab on migration towards different chemokines such as CXCL12, CXCL13 or to CXCR3 ligands, and to assess the functional consequences of altered adhesion molecule expression.
Epratuzumab binding was considerably higher on B-cells relative to other cell types assessed. No binding of epratuzumab was observed on T-cells, while weak non-specific binding of epratuzumab on monocytes was noted. On B-cells, binding of epratuzumab was particularly enhanced on CD27(negative) B-cells compared to CD27(positive) B-cells, primarily related to a higher expression of CD22 on CD27(negative) B-cells. Moreover, epratuzumab binding led to a decrease in the cell surface expression of CD62L and β7 integrin, while the expression of β1 integrin was enhanced. The effects on the pattern of adhesion molecule expression observed with epratuzumab were principally confined to a fraction of the CD27(negative) B-cell subpopulation and were associated with enhanced spontaneous migration of B-cells. Furthermore, epratuzumab also enhanced the migration of CD27(negative) B-cells towards the chemokine CXCL12.
The current data suggest that epratuzumab has effects on the expression of the adhesion molecules CD62L, β7 integrin and β1 integrin as well as on migration towards CXCL12, primarily of CD27(negative) B-cells. Therefore, induced changes in migration appear to be part of the mechanism of action of epratuzumab and are consistent with the observation that CD27(negative) B-cells were found to be preferentially reduced in the peripheral blood under treatment.
依帕珠单抗是一种人源化抗 CD22 单克隆抗体，作为一种治疗性抗体，正在研究用于非霍奇金淋巴瘤和系统性红斑狼疮（SLE），但其对 B 细胞的作用机制仍不清楚。依帕珠单抗治疗 SLE 患者会导致循环中 CD27（阴性）B 细胞减少，尽管依帕珠单抗在体外对 B 细胞的细胞毒性较弱。因此，评估了依帕珠单抗对粘附分子表达和 B 细胞迁移的潜在影响。
通过流式细胞术研究了依帕珠单抗在 SLE 患者 B 细胞亚群上的结合特异性和培养后粘附分子（CD62L、β7 整合素和β1 整合素）的表面表达。此外，进行了体外 Transwell 迁移实验，以分析依帕珠单抗对趋化因子（如 CXCL12、CXCL13 或 CXCR3 配体）迁移的影响，并评估改变粘附分子表达的功能后果。
依帕珠单抗与评估的其他细胞类型相比，与 B 细胞的结合明显更高。在 T 细胞上未观察到依帕珠单抗的结合，而在单核细胞上仅观察到较弱的非特异性依帕珠单抗结合。在 B 细胞上，依帕珠单抗的结合主要在 CD27（阴性）B 细胞上显著增强，而在 CD27（阳性）B 细胞上则显著增强，这主要与 CD27（阴性）B 细胞上 CD22 的表达较高有关。此外，依帕珠单抗结合导致细胞表面 CD62L 和β7 整合素表达减少，而β1 整合素表达增强。依帕珠单抗观察到的粘附分子表达模式的影响主要局限于 CD27（阴性）B 细胞亚群的一部分，并与 B 细胞的自发迁移增强有关。此外，依帕珠单抗还增强了 CD27（阴性）B 细胞向趋化因子 CXCL12 的迁移。
目前的数据表明，依帕珠单抗对粘附分子 CD62L、β7 整合素和β1 整合素的表达以及向 CXCL12 的迁移具有影响，主要是在 CD27（阴性）B 细胞上。因此，诱导的迁移变化似乎是依帕珠单抗作用机制的一部分，这与在治疗下外周血中发现 CD27（阴性）B 细胞优先减少的观察结果一致。
