The Igd-binding Domain of the Moraxella Igd-binding Protein Mid (Mid962-1200) Activates Human B Cells in the Presence of T Cell Cytokines.
From: Department of Laboratory Medicine, Malmö University Hospital, Lund University, SE-205 02, Malmö, Sweden.
Journal of leukocyte biology
- Publish Date: Feb 2006
- ISSN: 0741-5400
- Volume: 79
- Issue: 2
- Pages: 319-29
- Medium: Print
- Language: English
- Citation (JAMA): Nordström Therése, Jendholm Johan, Samuelsson Martin, et al. The Igd-binding Domain of the Moraxella Igd-binding Protein Mid (Mid962-1200) Activates Human B Cells in the Presence of T Cell Cytokines.. J. Leukoc. Biol. Feb 2006;79:319-29
Abstract
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 (MID(962-1200)). To prove the specificity of MID(962-1200) for IgD, a Chinese hamster ovary (CHO) cell line expressing membrane-anchored human IgD was manufactured. MID(962-1200) bound strongly to the recombinant IgD on CHO cells. Moreover, MID(962-1200) stimulated peripheral blood lymphocyte (PBL) proliferation 5- and 15-fold at 0.1 and 1.0 microg/ml, respectively. This activation could be blocked completely by antibodies directed against the CD40 ligand (CD154). MID(962-1200) 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 MID(962-1200), as revealed by a human cytokine protein array. MID(962-1200) fused to green fluorescent protein (GFP) bound to human B cells and activated PBL to the same degree as MID(962-1200). Taken together, MID is the only IgD-binding protein in Moraxella. Furthermore, the novel T cell-independent antigen MID(962-1200) may, together with MID(962-1200)-GFP, be considered as promising reagents in the study of IgD-dependent B cell activation.
Mesh Headings (Keywords): Adhesins, Bacterial, Animals, Antibodies, B-Lymphocytes, CD40 Ligand, CHO Cells, Cell Membrane, Cell Proliferation, Cells, Cultured, Cricetinae, Cytokines, Green Fluorescent Proteins, Humans, Immunoglobulin D, Interleukin-6, Moraxella (Branhamella) catarrhalis, T-Lymphocytes, Time Factors
Check for Full Text / PubMed Unique Identifier (PMID): 16301327
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