isotypswitch

Isotypswitch is a nonstandard term that has appeared in some discussions as a colloquial reference to isotype switching, a process in the adaptive immune system. The conventional name is isotype switching or class switch recombination (CSR). It describes the rearrangement of the immunoglobulin heavy-chain constant region genes in activated B cells, allowing antibodies to switch the effector function without changing antigen specificity.

Mechanism and locus: CSR is initiated by activation-induced cytidine deaminase (AID), which introduces nicks and double-strand breaks in switch (S) regions upstream of constant-region gene segments. DNA repair ligates a different constant-region gene segment to the variable (V) region, producing a new antibody isotype (for example from IgM to IgG, IgA, or IgE). The process typically occurs after antigen exposure and T cell help, often in germinal centers of lymphoid organs.

Regulation and outcomes: Cytokines from helper T cells influence isotype choice (e.g., IL-4 promotes certain isotypes; TGF-β promotes IgA in many species). The result is a population of antibodies that retains antigen specificity but gains altered effector functions, such as Fc receptor binding, complement activation, and enhanced mucosal immunity.

Notes: The term isotypswitch is not widely used in the scientific literature and may be encountered as a misspelling or informal shorthand. The standard terminology to consult is “isotype switching” or “class switch recombination.”

See also: Isotype switching, Class switch recombination, Antibody isotype.