Function of C3 in a humoral response: iC3b/C3dg bound to an immune complex generated with natural antibody and a primary antigen promotes antigen uptake and the expression of co-stimulatory molecules by all B cells, but only stimulates immunoglobulin synthesis by antigen-specific B cells
| Autor: | G D Ross, B P Thornton, Vaclav Vetvicka |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
Immunology
Antigen presentation Naive B cell B-cell receptor Enzyme-Linked Immunosorbent Assay chemical and pharmacologic phenomena Antigen-Antibody Complex Lymphocyte Activation complex mixtures Antigen Antibody Specificity medicine Humans Immunology and Allergy Cells Cultured B cell Antigen Presentation B-Lymphocytes biology Antigen processing Receptors IgG Antibodies Monoclonal hemic and immune systems Original Articles Molecular biology Lymphocyte Function-Associated Antigen-1 biological factors B-1 cell medicine.anatomical_structure Immunoglobulin M Complement C3d Immunoglobulin G Antibody Formation Complement C3b Hemocyanins Leukocytes Mononuclear biology.protein Receptors Complement 3d Antibody therapeutics |
| Zdroj: | Clinical and Experimental Immunology. 104:531-537 |
| ISSN: | 1365-2249 0009-9104 |
| DOI: | 10.1046/j.1365-2249.1996.57761.x |
| Popis: | SUMMARY Previous studies have shown that an optimal humoral response to a primary protein antigen requires C3 and CR2 (CD21). Sera from non-immunized donors contain natural IgM and IgG antibodies to the primary antigen keyhole limpet haemocyanin (KLH), and these have been previously shown to form immune complexes (IC) that activate the classical pathway of C, fixing iC3b/C3dg onto the KLH antigen. Such KLH IC bind to CR2 on KLH-non-specific B lymphocytes, resulting in antigen processing and MHC class II-dependent presentation to KLH-specific helper T cells. KLH IC also induce B lymphocytes to express the CD80 co-stimulatory molecule via simultaneous CR2 ligation with C3 and FcγRII (CD32) stimulation by IgG natural antibody. The current study demonstrated that KLH IC ligation to either CR2 or FcγRII resulted in activation of a second co-stimulatory molecule, LFA-1 (CD11a, CD18). The possibility of polyclonal B cell stimulation by the presentation of KLH-iC3b/C3dg by antigen-non-specific B cells was excluded by demonstration that in vitro cultivation of peripheral blood mononuclear cells (PBMC) with KLH-iC3b/C3dg elicited only anti-KLH, and did not stimulate synthesis of antibodies to hepatitis C virus (HCV) or tetanus toxoid (TT). Of greatest significance, a specific anti-KLH response was only detectable in cultures stimulated with KLH-iC3b/C3dg and not in cultures stimulated with KLH alone or KLH-IgG. Thus, iC3b/C3dg that was bound to a primary protein antigen enhanced recognition and specific immunoglobulin synthesis by antigen-specific B cells, even though the antigen was taken up and processed via CR2 by both antigen-specific and non-specific B cells. |
| Databáze: | OpenAIRE |
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