Distinct sequences in the cytoplasmic domain of complement receptor 2 are involved in antigen internalization and presentation.
B cells express randomly rearranged surface Ig that forms part of a multiprotein complex known as the B cell receptor (BCR). Recognition of Ag via this receptor results in its capture, internalization, proteolysis and presentation to CD4+ T cells. The recognition of Ag by CD4+ T cells is critical for the selection of individual B cells, leading to the eventual secretion of a high affinity version of the BCR as an effective circulating Ab. B cells also express other receptors that recognize Ags associated with components of innate immunity. One of these receptors, CR2, binds Ags coated with activated complement components. Studies have shown that cross-linking CR2 and the BCR with complement-tagged Ags leads to enhanced Ag presentation by B cells. In addition, Ags targeted to B cell CR2 in the absence of BCR coligation are also efficiently presented to T cells. In this report, we identify several distinct sequences within the cytoplasmic domain of mouse CR2 (mCR2) that are essential for mCR2-mediated Ag presentation in both the presence and the absence of BCR cross-linking. The finding that distinct sequences in the cytoplasmic domain of mCR2 are essential for BCR-independent Ag presentation leads us to propose a novel role for CR2.
Institute of Cell, Animal and Population Biology, University of Edinburgh, Edinburgh EH9 3JT, UK.
Denise V
DV
Barrault
Andrew M
AM
Knight
D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000235:genetics; D015703:Antigens, CD / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D051925:CD79 Antigens; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D003593:Cytoplasm / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D019281:Dimerization; D004705:Endocytosis / Q000235:genetics / Q000276:immunology*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary / Q000235:genetics; D011947:Receptors, Antigen, B-Cell / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D017464:Receptors, Complement 3d / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000502:physiology*
D015703:Antigens, CD; D051925:CD79 Antigens; C497881:CD79A protein, human; C497883:CD79B protein, human; C497882:Cd79a protein, mouse; C497884:Cd79b protein, mouse; D011947:Receptors, Antigen, B-Cell; D017464:Receptors, Complement 3d