TY - JOUR
T1 - Processing and MHC class II presentation of exogenous soluble antigen involving a proteasome-dependent cytosolic pathway in CD40-activated B cells
AU - Becker, Hans Jiro
AU - Kondo, Eisei
AU - Shimabukuro-Vornhagen, Alexander
AU - Theurich, Sebastian
AU - von Bergwelt-Baildon, Michael S.
N1 - Publisher Copyright:
© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2016/8/1
Y1 - 2016/8/1
N2 - Activated B cells have the capacity to present antigen and induce immune responses as potent antigen-presenting cells (APCs). As in other APCs, antigen presentation by B cells involves antigen internalization, antigen processing, and peptide loading onto MHC molecules. However, while the mechanism of antigen processing has been studied extensively in other APCs, this pathway remains elusive in B cells. The aim of this study was to investigate the MHC class II processing pathway in CD40-activated B cells (CD40Bs), as a model for activated, antigen-presenting B cells. Using CMV pp65 as a model antigen, we evaluated processing and presentation of the CD4 + T-cell epitope 509-523 (K509) by human CD40Bs in ELISPOT assays. As expected, stimulation of specific CD4 + T-cell clones was attenuated after pretreatment of CD40Bs with inhibitors of classic class II pathway components. However, proteasome inhibitors such as epoxomicin limited antigen presentation as well. This suggests that the antigen is processed in a non-classical, cytosolic MHC class II pathway. Further experiments with truncated protein variants revealed involvement of the proteasome in processing of the N and C extensions of the epitope. Access to the cytosol was shown to be size dependent. Epoxomicin sensitivity exclusively in CD40B cells, but not in dendritic cells, suggests a novel processing mechanism unique to this APC. Our data suggest that B cells process antigen using a distinct, non-classical class II pathway.
AB - Activated B cells have the capacity to present antigen and induce immune responses as potent antigen-presenting cells (APCs). As in other APCs, antigen presentation by B cells involves antigen internalization, antigen processing, and peptide loading onto MHC molecules. However, while the mechanism of antigen processing has been studied extensively in other APCs, this pathway remains elusive in B cells. The aim of this study was to investigate the MHC class II processing pathway in CD40-activated B cells (CD40Bs), as a model for activated, antigen-presenting B cells. Using CMV pp65 as a model antigen, we evaluated processing and presentation of the CD4 + T-cell epitope 509-523 (K509) by human CD40Bs in ELISPOT assays. As expected, stimulation of specific CD4 + T-cell clones was attenuated after pretreatment of CD40Bs with inhibitors of classic class II pathway components. However, proteasome inhibitors such as epoxomicin limited antigen presentation as well. This suggests that the antigen is processed in a non-classical, cytosolic MHC class II pathway. Further experiments with truncated protein variants revealed involvement of the proteasome in processing of the N and C extensions of the epitope. Access to the cytosol was shown to be size dependent. Epoxomicin sensitivity exclusively in CD40B cells, but not in dendritic cells, suggests a novel processing mechanism unique to this APC. Our data suggest that B cells process antigen using a distinct, non-classical class II pathway.
KW - B cells
KW - T cells
KW - antigen Presentation/Processing
KW - antigens/Peptides/Epitopes
KW - dendritic cells
KW - human
KW - vaccination
UR - http://www.scopus.com/inward/record.url?scp=84978138309&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84978138309&partnerID=8YFLogxK
U2 - 10.1111/ejh.12699
DO - 10.1111/ejh.12699
M3 - Article
C2 - 26561366
AN - SCOPUS:84978138309
VL - 97
SP - 166
EP - 174
JO - European Journal of Haematology
JF - European Journal of Haematology
SN - 0902-4441
IS - 2
ER -