What is CD21 a marker for?
CD21, which recognize activated products of complement 3 is predominantly expressed on mature B cells and follicular dendritic cells [17] and is an important receptor for uptake and retention of immune complexes. In the absence of CD21 expression, survival of memory B cells is markedly impaired [18].
What is the role of follicular dendritic cells?
Follicular dendritic cells (FDCs) have important functions in the selection of memory B lymphocytes during germinal center reactions (GCR). They present native antigens to potential memory cells, of which only B cells with high affinity B cell receptors (BCR) can bind.
What is the origin of follicular dendritic cells?
Follicular dendritic cells (FDC) are cells of the immune system found in primary and secondary lymph follicles (lymph nodes) of the B cell areas of the lymphoid tissue. Unlike dendritic cells (DC), FDCs are not derived from the bone-marrow hematopoietic stem cell, but are of mesenchymal origin.
Where are follicular dendritic cells found?
lymph node germinal follicles
Follicular dendritic cells (FDCs) are found in the lymph node germinal follicles (Figure 5-2) and have several different functions, including activation of B cells and maintenance of immunologic memory.
Do all B cells express CD21?
The surface levels of CD21 on B cells vary depending on the maturation stage of the cell (Table 1). Early transitional (T1) B cells express low levels 45, 46, the majority of circulating B cells including naïve and memory cells express CD21, whereas plasmablasts and plasma cells lack or express low levels 45, 47.
What are CD21 low B cells?
CD21low B cells of CVID are polyclonal, unmutated B cells with an increased replication history and autoreactive specificity. (A) Sorted naïve B cells of 4 HD and 8 CVID patients as well as CD21low B cells of 8 CVID patients were spectratyped for the expression of Vh1 through Vh6 regions of IgM.
Why are follicular helper T cells important?
T follicular helper cells (Tfh) are a specialized subset of CD4+ T cells that were first identified in the human tonsil. They play a critical role in protective immunity helping B cells produce antibody against foreign pathogens.
Where do we found follicular dendritic cells and Langerhans cells?
Follicular dendritic cells (FDCs) are cells of stromal origin that are indispensable for secondary lymphoid organ (SLO) and tertiary lymphoid organ (TLO) development and maintenance. They are located in the central region of primary follicles and in the light zone of germinal centers [GCs; (1, 2)].
Do follicular dendritic cells have MHC?
Follicular dendritic cells (FDCs) present in lymphoid follicles play a critical role in germinal center reactions. FDCs have been reported to express MHC class II molecules, suggesting an additional role in the presentation of not only native, but also processed Ag in the form of peptide-loaded MHC class II.
Do dendritic cells stimulate B cells?
Dendritic cells (DC) have recently been shown to play an important role in B-cell function. We have previously shown that DC can capture and retain unprocessed antigen in vitro and in vivo, and can transfer this antigen to naive B cells to initiate antigen-specific antibody responses.
How many types of dendritic cells are there?
Three types of DCs have been defined in human blood: the CD1c+ myeloid DCs, the CD141+ myeloid DCs and the CD303+ plasmacytoid DCs. This represents the nomenclature proposed by the nomenclature committee of the International Union of Immunological Societies.
What are the patterns of CD21 and CD23?
Patterns of CD21 and CD23 expression by the follicular dendritic cells. Pattern 1 describes diffuse staining of FDCs in the germinal center while pattern 2 demonstrates the peripheral staining in a “crescetic” fashion.
Where are CD21 and CD35 located in lymph nodes?
In reactive lymph nodes, FDCs of both primary and secondary follicles are recognized by CD21 and CD35. FDCs in germinal center (GC) light zones (LZ) additionally upregulate CD23 and CD32 [ 9 ].
What is the function of follicular dendritic cells?
Follicular dendritic cells (FDCs) are a unique type of cell characterized by localization within lymphoid follicles, intricately entangled cytoplasmic processes, the ability to trap and retain immune complexes, and expression of molecules involved in the proliferation and differentiation of B cells [ 9 ].
How does CD21 bind to antigen in B cells?
Forms a complex with CD19, CD81 and CD225 in the membrane of mature B cells; complex is often called the B cell coreceptor complex, because CD21 binds to antigens through attached C3d (or iC3b or C3dg) when the membrane IgM binds to the antigen, which results in a greatly enhanced response B cell response to the antigen ( Wikipedia )