Immune response class switching

Class (Isotype) Switching Occurs During Immune Responses... 

As compared to DCs, B cells are very poor APCs and play a major role as source for antibodies. Upon stimulation by antigens and in the presence of T cells at the border of the T-cell-B-cell area, adjacent to follicles, B cells become antibody-secreting cells and eventually form a germinal center (GC) response. GCs are specialized follicles for B-cell expansion, somatic hypermutation, and class switch recombination, processes that are regulated by T cells, follicular DCs, and other cells. In this process of B-cell maturation, Tregs seem to play a critical role, as in several immune diseases, which are characterized by aberrant antibody... 

Helper T-cell 2 Th2 CD4-H Coordination of immune response, particularly activation of antibody production by B-cells and responsible for switching class from IgM to IgE. 

Neuroimmunological reactions. The humoral immune response in CNS is different from the immune response usually observed in blood. As a main difference, we find no switch from the IgG-class response to a more speciflc IgG-class response in the course of inflammatory disease. The pattern of intrathecal IgG/IgA/IgM synthesis remains rather constant and depends on the causes, pathophysiology, and localization of the disease process (R4). 

Antibodies of the IgG, IgA and IgE classes are made later than IgM during a primary immune response, but account for most of the antibody that is made during a memory response. Although isotype switching and affinity maturation are independent processes, they usually occur simultaneously (Fish et al., 1989), so that the increased affinity of bivalent antibodies of isotypes other than IgM is rapidly enhanced. IgG antibody is the predominant isotype in plasma and lymph, while IgA antibody predominates at mucosal surfaces and in secretions from these surfaces. 

The wide variety of immunoglobulins required for a full immune response in humans and mice results from the combinatorial joining of immunoglobulin gene (Ig) V, D, and J gene segments from class switch recombination and from somatic hypermutation of variable (V) regions (see Chapter 11). Several polymerases have been implicated in the DNA synthesis required for development of a normal immune system. 

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