Cerutti A, Trentin L, Zambello R, Sancetta R, Milani A, Tassinari C, Adami F, Agostini C, Semenzato G
Department of Clinical and Experimental Medicine, Padua University School of Medicine, Italy.
J Immunol. 1996 Sep 1;157(5):1854-62.
The CD5 molecule is expressed on T cells and, at a lower density, on a minor B cell subset (CD5+ B cells). The pan-B Ag CD72 was recently identified as the CD5 counterstructure, and several data suggest the involvement of this ligand pair in T-B cell cognate interaction. However, the functional role of CD5 and CD72 molecules within the B cell compartment is still unknown. In this work we studied umbilical cord blood CD5+ B cells (B-1a), adult splenic CD5- B cells (B-2), and CD5+ B cells from patients with chronic lymphocytic leukemia. Flow cytometry analysis and proliferation assays were used to determine 1) the ability of B-1a and B-2 cells to coexpress functionally relevant counterligands other than CD5 and CD72, and 2) the signaling capacity of CD5 and CD72 in terms of B cell activation and proliferation. To this purpose, freshly isolated or preactivated normal and neoplastic B cells were cultured with agonistic anti-CD5 or anti-CD72 mAbs in the presence or the absence of cytokines equipped with B cell activity. Our data demonstrate that CD5 and CD72 molecules are coexpressed with other ligand pairs usually involved in T-B cell cognate interaction on B-1a cells, but not on B-2 cells. CD5 and/or CD72 engagement delivers critical costimulatory signals in B-1a, B-2, and B cells from patients with chronic lymphocytic leukemia, but with different requirements and patterns. Besides suggesting the potential involvement of B-1a lymphocytes in B-B cell interactions during T-independent B cell responses, our results indicate that CD5 and CD72 counterstructures play a functional role in the B cell compartment.
CD5分子在T细胞上表达，在一小部分B细胞亚群（CD5+B细胞）上也有较低密度的表达。全B抗原CD72最近被确定为CD5的配对结构，多项数据表明该配体对参与T-B细胞同源相互作用。然而，CD5和CD72分子在B细胞区室中的功能作用仍不清楚。在这项研究中，我们研究了脐带血CD5+B细胞（B-1a）、成人脾脏CD5-B细胞（B-2）以及慢性淋巴细胞白血病患者的CD5+B细胞。采用流式细胞术分析和增殖试验来确定：1）B-1a和B-2细胞共表达除CD5和CD72之外功能相关的配对配体的能力；2）就B细胞活化和增殖而言，CD5和CD72的信号传导能力。为此，将新鲜分离的或预先激活的正常和肿瘤性B细胞与激动性抗CD5或抗CD72单克隆抗体一起培养，同时存在或不存在具有B细胞活性的细胞因子。我们的数据表明，CD5和CD72分子与通常参与T-B细胞同源相互作用的其他配体对在B-1a细胞上共表达，但在B-2细胞上不共表达。CD5和/或CD72的结合在B-1a、B-2以及慢性淋巴细胞白血病患者的B细胞中传递关键的共刺激信号，但具有不同的要求和模式。除了提示B-1a淋巴细胞在非T细胞依赖性B细胞反应期间可能参与B-B细胞相互作用外，我们的结果还表明CD5和CD72配对结构在B细胞区室中发挥功能作用。
