1 Bioanalytikeruddannelsen, Det Sundhedsfaglige og Teknologiske Fakultet, Professionshøjskolen Metropol, University Colleges2 Institute for Inflammation Research, Department of Infectious Diseases and Rheumatology, section 7521, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark.3 Blood Bank, KI2034, Department of Clinical Immunology, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark.4 Bioanalytikeruddannelsen, Det Sundhedsfaglige og Teknologiske Fakultet, Professionshøjskolen Metropol, University Colleges
B cells may play both pathogenic and protective roles in T-cell mediated autoimmune diseases such as multiple sclerosis (MS). These functions relate to the ability of B cells to bind and present antigens. Under serum-free conditions we observed that 3–4% of circulating B cells from healthy donors were capable of binding the MS-associated self-antigen myelin basic protein (MBP) and of presenting the immunodominant peptide MBP85-99, as determined by staining with the mAb MK16 recognising the peptide presented by HLA-DR15-positive cells. In the presence of serum, however, the majority of B cells bound MBP in a complement-dependent manner, and almost half of the B cells became engaged in presentation of MBP85-99. Even though complement receptor 1 (CR1, CD35) and CR2 (CD21) both contributed to binding of MBP to B cells, only CR2 was important for the subsequent presentation of MBP85-99. A high proportion of MBP85-99 presenting B cells expressed CD27, and showed increased expression of CD86 compared to non-presenting B cells. MBP-pulsed B cells induced a low frequency of IL-10-producing CD4+ T cells in 3 out of 6 donors, indicating an immunoregulatory role of B cells presenting MBP-derived peptides. The mechanisms described here refute the general assumption that B-cell presentation of self-antigens requires uptake via specific B-cell receptors, and may be important for maintenance of tolerance as well as for driving T-cell responses in autoimmune diseases.
P L O S One, 2014, Vol 9, Issue 11
health; Journal Article; Research Support, Non-U.S. Gov't