From Proteopedia

H. sapiens mIgM B Cell Receptor

spinqualitylabelsall models mIgM B Cell Receptor 7XQ8 Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image Contents 1 Introduction 2 Structure 3 Antigen Binding Site 4 Heavy Chain Interactions (Iga and IgB) 5 Transmembrane Interactions 6 Function 7 Proposed Conformational Changes 8 Signal Pathway Introduction Structure Figure 2. The Signal pathway for the response to an antigen by the B-cell receptor. Illustration reproduced courtesy of Cell Signaling Technology, Inc. (www.cellsignal.com). Antigen Binding Site Figure 1. Overview of the human B Cell Receptor and its structural components. Used with permission under Wikimedia Commons. The binding of an antigen to the human B Cell receptor is identical to other common soluble antibodies (such as IgG, IgA, IgM, IgE, or IgD). The antibody portion of the B Cell Receptor is roughly "Y" shaped and consists of two identical and two identical chains creating two similar epitope or binding regions[1]. Thus, two antigen molecules can bind independent of one another to produce a response. Within this structure, there are both constant and variable regions. The stem of the "Y" is a (Fc) composed of only heavy chain interactions[1]. The two heavy chains then branch at a flexible . These interact individually with one light chain creating two Fab fragments or branches of the "Y"[1]. Each additionally contains a (Fv) and a [1]. The variable region sits on top of the constant region and consists of hyper-variable loops which are random coils of amino acids that are unique to an antibody and exposed to allow specific recognition of an antigen[1]. Furthermore, the light chains interact with the heavy chains via weak intermolecular forces and disulfide bridges[1]. Therefore, binding to an antigen is processed through intermolecular interactions and is specific due to unique hyper variable loop sequences. Heavy Chain Interactions (Iga and IgB) Transmembrane Interactions Function Proposed Conformational Changes Signal Pathway

Medical Relevancy

Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. 5th edition. New York: Garland Science; 2001.

Disease

B-cells and their respective receptors play an important role in the immune response. Therefore, if the receptors were to not function properly, there would be damaging consequences. Autoimmune disease is suggested to occur when somatic cells are recognized as foreign antigens and the body tries to eliminate them. Although the exact mechanism of disease has not been provided, it is thought that B-cell receptors are an essential part of these diseases due to their function and role in the immune systems. B-cell receptors are improperly recognizing somatic cells from different tissues depending on the disease and elicit the production of antibodies against them (autoantibodies). This causes destruction of these cell types. Examples of these diseases include rheumatoid arthritis where the lining of joints is targeted and degraded, multiple sclerosis which targets the myelin sheath that surrounds nerve cells, type 1 diabetes mellitus where the insulin producing cells are targeted for destruction, and systematic lupus erythematosus where multiple organ systems are targeted (skin, brain, lungs, and kidneys are common targets).

Therapeutics

References

1. ↑ ^{1.0 1.1 1.2 1.3 1.4 1.5} Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. 5th edition. New York: Garland Science; 2001.