China
Africa
Explore chapters and articles related to this topic
Primary Immunodeficiencies
Published in Gérard Chaouat, The Immunology of the Fetus, 2020
Alain Fischer, Durandy Anne, Claude Griscelli
Epstein-Barr virus (EBV) has an elective tropism for B-lymphocytes which express a specific receptor (the CD21-C3d receptor). Infected B-cells are activated and proliferate in an uncontrolled way. In normal subjects, specific cytotoxic T-cells limit the EBV-induced B-cell proliferation and control the disease. In patients with severe primary (SCID) or acquired ID (AIDS, transplantation), an uncontrolled EBV-induced polyclonal or monoclonal B-cell proliferation can occur and provoke death.38
Overview of the mucosal immune system structure
Published in Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald, Principles of Mucosal Immunology, 2020
Reinhard Pabst, Per Brandtzaeg
The complement receptors CR1/CR2 (CD35/CD21) are crucial in the germinal center reaction. CD21 is expressed abundantly on both B cells and FDCs and may thus function not only by localizing antigen to the FDCs but also by lowering the threshold of B-cell activation via recruitment of CD19 into the BCR. Activation of complement on FDCs bearing immune complexes is controlled by regulatory factors, but some release of inflammatory mediators may induce edema that facilitates dispersion of FDC-derived “immune complex-coated bodies,” or iccosomes, thereby enhancing the BCR-mediated uptake of their contained antigens by the B cells.
B Cells and Humoral Immunity
Published in Constantin A. Bona, Francisco A. Bonilla, Textbook of Immunology, 2019
Constantin A. Bona, Francisco A. Bonilla
CD 19 and CD21 occur on the B cell membrane in a complex with CD81 (ΤΑΡΑ-1) and Leu 13. This complex may also associate with class II histocompatibility molecules. This complex has an important role in B cell activation (see below). CD21 (also called CR2) is the receptor for the C3d complement fragment and Epstein-Barr virus (EBV). CD21 is found on the majority of lymphoid organ B cells, but is infrequent among peripheral blood B cells. Aggregated C3d provides a growth signal for B cells; CD21 is not expressed after B cell activation.
Autoimmune disorders associated with common variable immunodeficiency: prediction, diagnosis, and treatment
Published in Expert Review of Clinical Immunology, 2022
Niloufar Yazdanpanah, Nima Rezaei
Complement receptor type 2 (CR2, also known as CD21) is expressed on different immune cells. On B cells, CD21 contributes to the formation of a complex with CD19 and CD81. The complex acts as a coreceptor for the B cell receptor (BCR), which decreases the threshold of B cell activation upon stimulation [43,44]. B cells express CD21 based on their maturation stage; circulating naïve B cells and memory B cells express higher levels of CD21 compared to plasma cells [45]. A genetic defect of CD21 is associated with hypogammaglobulinemia [46]. Current data underpins that CD21low B cells derive from either memory B cells or plasma cells following chronic stimulation with extrinsic antigens [47]. CD21low B cells have shown weak proliferation through BCR signaling and demonstrated a shorter half-life compared with CD21+ B cells. Furthermore, despite representing an activated phenotype, CD21low B cells express inhibitory receptors. On the other hand, expansion of CD21low B cells was reported in autoreactive clones of immune cells [48–50]. Rakhmanov et al. described CD21low B cells as pre-activated polyclonal cells, which represent an attenuated function and are mainly localized in peripheral tissues [51]. Following provocation via CD40L, IL-2, and IL-10, CD21low B cells release higher levels of IgM in comparison with naïve B cells; high IgM level is proposed to be linked with the development of autoimmune conditions in CVID patients [14,52,53].
HSC70 is a novel binding partner involved in the capture of immunoglobulins on B cells in the NOD mouse
Published in Autoimmunity, 2022
Emma Renman, Rifat Ekici, Mia Sundström, Kristina Lejon
When investigating the antibody binding capacity of different B cell subsets in spleen, the most substantial binding was observed among the marginal zone B cell subset in both mouse strains. It is known that ICs can be captured on the surface of B cells in a complement receptor-dependent manner, which could be one explanation to the high binding capacity of CD21high expressing marginal zone B cells [1]. Also, NOD mice have an increased marginal zone/follicular B cell ratio compared to C57BL/6 [20], which suggests that the increased Ig capturing by NOD B cells could be explained by the marginal zone B cells. However, based on our data we rule out this possibility, as the most pronounced difference in antibody capture between the strains could be observed for the ABC (CD19+CD21/35−CD23−) subset.
CARMIL2 Immunodeficiency with Epstein Barr Virus Associated Smooth Muscle Tumor (EBV-SMT). Report of a Case with Comprehensive Review of Literature
Published in Fetal and Pediatric Pathology, 2022
Mukul Vij, Meena Sivasankaran, Dhaarani Jayaraman, Srinivas Sankaranarayanan, Vimal Kumar, Deenadayalan Munirathnam, Julius Scott
Pathogenetic mechanism of EBV-SMT is still debated but it has been suggested to be related with an uncontrolled proliferation of EBV-infected lymphocytes which fuses with smooth muscle cells and induce neoplastic transformation [30]. EBV-SMT in patients with HIV have been shown to express complement receptor 2 (CR2 or CD21), indicating that EBV-infected lymphocytes play a role in pathogenesis [31]. Normal smooth muscle cells express the CD21 receptor and can be directly infected with EBV. Facilitating and promoting replication within these cells has also been proposed as another pathomechanism [32]. A majority of solid organ and bone marrow transplant-associated EBV-SMT and all analyzed cases of EBV-SMT in patients with PID are negative for CD21 indicating undiscovered pathways in tumorigenesis [29]. It has also been postulated that immunosuppression may play a role in allowing abnormal EBV cellular entry. EBV-SMT has been shown to demonstrate EBV type III latency pattern, i.e., cells are positive for EBV nuclear antigen 2 (EBNA2), EBNA3, and LMP1. Ong et al investigated molecular pathways in post organ transplant EBV-SMT and suggested activation of the mTOR/Akt pathway [33]. This activation has been shown to be triggered by EBV protein LMP2A suggesting critical role of EBV in tumorigenesis [33]. Methylation of RASSF1A and promoter hypermethylation of RARβ, GSTP1, DAPK, and p14 were also observed [33]. Increased expression of proto-oncogene MYC and microRNA expression profile which is related to smooth muscle differentiation but not EBV infection has also been also reported in post-transplant EBV-SMT [32, 34].