The IgD-binding domain of the Moraxella IgD-binding protein MID (MID962-1200) activates human B cells in the presence of T cell cytokines

Journal of Leukocyte Biology

Therése Nordström¹  Martin Samuelsson¹  Arne Forsgren¹  Johan Jendholm¹  Kristian Riesbeck¹ 

[1] Medical Microbiology, Department of Laboratory Medicine, Malmö University Hospital, Lund University, Malmö, SwedenMedical Microbiology, Department of Laboratory Medicine, Malmö University Hospital, Lund University, Malmö, SwedenMedical Microbiology, Department of Laboratory Medicine, Malmö University Hospital, Lund University, Malmö, Sweden

关键词: B lymphocyte;    immunoglobulin D;    GFP;    Moraxella catarrhalis;   

DOI  :  10.1189/jlb.0205065

学科分类：生理学

来源: Federation of American Societies for Experimental Biology

【 摘 要 】

Moraxella catarrhalis immunoglobulin D (IgD)-binding protein (MID) is an outer membrane protein with specific affinity for soluble and cell-bound human IgD. Here, we demonstrate that mutated M. catarrhalis strains devoid of MID show a 75% decreased activation of human B cells as compared with wild-type bacteria. In contrast to MID-expressing Moraxella, the MID-deficient Moraxella mutants did not bind to human CD19+ IgD+ B cells. The smallest MID fragment with preserved IgD-binding capacity comprises 238 amino acids (MID962-1200). To prove the specificity of MID962-1200 for IgD, a Chinese hamster ovary (CHO) cell line expressing membrane-anchored human IgD was manufactured. MID962-1200 bound strongly to the recombinant IgD on CHO cells. Moreover, MID962-1200 stimulated peripheral blood lymphocyte (PBL) proliferation 5- and 15-fold at 0.1 and 1.0 μg/ml, respectively. This activation could be blocked completely by antibodies directed against the CD40 ligand (CD154). MID962-1200 also activated purified B cells in the presence of interleukin (IL)-2 or IL-4. An increased IL-6 production was seen after stimulation with MID962-1200, as revealed by a human cytokine protein array. MID962-1200 fused to green fluorescent protein (GFP) bound to human B cells and activated PBL to the same degree as MID962-1200. Taken together, MID is the only IgD-binding protein in Moraxella. Furthermore, the novel T cell-independent antigen MID962-1200 may, together with MID962-1200–GFP, be considered as promising reagents in the study of IgD-dependent B cell activation.

【 授权许可】

Unknown