B cell development starts in the fetal liver switches

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B cell development starts in the FETAL LIVER -Switches to the bone marrow during gestation -After birth: B cell development will continue in the bone marrow -B-cell precursor rearranges its immunoglobulin genes >DNA rearrangement: Somatic recombination to form rearranged gene >Generation of B-cell receptors in the bone marrow -Immature B cell bound to the cell-surface antigen is removed from the repertoire >Must have tolerance and clonal deletion of self-reactivity > Negative selection tolerance 29) What is a germinal center in the context of B cell activation? B cell zone are the primary and secondary (germinal center) FOLLICLE regions. >Germinal centers release B cells that differentiate into plasma cells or memory cells. Germinal centers form during the adaptive immune response. the B-cell follicles of the lymph nodes expand as B lymphocytes proliferate to form germinal centers Germinal centers or germinal centres (GCs) are sites within secondary lymphoid organs – lymph nodes and the spleen where mature B cells proliferate, differentiate, and mutate their antibody genes (through somatic hypermutation aimed at achieving higher affinity), and switch the class of their antibodies Somatic hypermutation generally involves individual point mutations that change only a single amino acid. Somatic hypermutation is normally restricted to B-cells that are proliferating in germinal centers. When a somatic-hypermutation improves the affinity of a B-cell-receptor for a specific antigen,
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30) Explain what control the homing of B cells into the follicles? Is there a difference in chemokine production between the dark and light zone of a germinal center? Explain homing? Dark zone (centroblasts) – don’t express CXCR4 and CXCR5 (b-cells do); produce CXCL12 Light zone (centrocytes) – express CXCR5 ; produces CXCL13 (because of FDCs? Follicular dendritic cells)? 4 recognizes 12 5 recognizes13 So yes, there is a difference? Does light zone produce any chemokines? 31) What is the function of follicular dendritic cells? The B-cell zone contains a network of follicular dendritic cells ( FDCs) , which are concentrated mainly in the area of the follicle most distant from the central arteriole. FDCs have long processes, from which they get their name, and these are in contact with B cells. FDCs are a distinct type of cell from the dendritic cells we have encountered previously (see Section 1-3), in that they are not leukocytes and are not derived from bone marrow precursors; in addition, they are not phagocytic and do not express MHC class II proteins. FDCs seem to be specialized to capture antigen in the form of immune complexes-complexes of antigen, antibody, and complement. The immune complexes are not internalized but remain intact on the surface of the FDC, where the antigen can be recognized by B cells. FDCs are also important in the development of B-cell follicles.
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---fdcs capture peptides; have complement receptors; b cell receptors FDCs come from mesenchymal cells ; have receptors to hold peptides ; normal dendritic
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