This allows different daughter cells from the same activated B cell to produce antibodies of different isotypes or subtypes (e.g. Instead, the antibody retains affinity for the same antigens, but can interact with different effector molecules. Since the variable region does not change, class switching does not affect antigen specificity. During this process, the constant region portion of the antibody-heavy chain is changed, but the variable region of the heavy chain stays the same (the terms “constant” and “variable” refer to changes or lack thereof between antibodies that target different epitopes). Immunoglobulin class switching (or isotype switching, or isotypic commutation, or class switch recombination (CSR)) is a biological mechanism that changes a B cell’s production of antibody from one class to another for example, from an isotype called IgM to an isotype called IgG. If these activated B cells encounter specific signaling molecules via their CD40 and cytokine receptors (both modulated by T helper cells), they undergo antibody class switching to produce IgG, IgA or IgE antibodies (from IgM or IgD) that have defined roles in the immune system. In this activated form, the B cell starts to produce antibody in a secreted form rather than a membrane-bound form. B cell activation follows engagement of the cell-bound antibody molecule with an antigen, causing the cell to divide and differentiate into an antibody-producing cell, called a plasma cell. B cells begin to express both IgM and IgD when they reach maturity the co-expression of both of these immunoglobulin isotypes renders the B cell ‘mature’ and ready to respond to an antigen. Immature B cells, which have never been exposed to an antigen, are known as naïve B cells and express only the IgM isotype in a cell surface bound form. The antibody isotype of a B cell changes during cell development and activation. They are each named with an “Ig” prefix that stands for immunoglobulin (another name for antibody) and differ in their biological properties, functional locations, and ability to deal with different antigens. In placental mammals there are five antibody isotypes: IgA, IgD, IgE, IgG and IgM. ).Īntibodies can come in different varieties, known as isotypes or classes. The antibody retains affinity for the same antigens, but can interact with different effector molecules.During class switch recombination the constant region portion of the antibody-heavy chain is changed, but the variable region of the heavy chain stays the same thus, class switching does not affect antigen specificity.If activated B cells encounter specific signaling molecules via their CD40 and cytokine receptors (both modulated by T helper cells), they undergo antibody class switching to produce IgG, IgA or IgE antibodies that have defined roles in the immune system.B cells begin to express both IgM and IgD when they reach maturity and renders the B cell ‘mature’ and ready to respond to antigen. Immature B cells have never been exposed to an antigen and are known as naïve B cells. The antibody isotype of a B cell changes during cell development and activation.
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