Introduction

Significance and Background

The adaptive immune response possessed by vertebrate animals owes much of its function to B cells. These specialized immune cells produce antibodies and immunoglobulins (Ig), the membrane bound equivalent to antibodies. B cells can produce a variety of Ig compounds including IgG, IgA, IgE, IgD, and IgM. These antibodies and Ig compounds bind to specific compounds called antigens. When an IgM combines with a B cell receptor (BCR), it can then send a signal in the form of a conformational change through the B cell membrane to stimulate the production of more antibodies that recognize that antigen.

The structure of the IgM BCR complex was determined by two research groups using Cryo EM. They also determined the structure of IgG.

History and Discovery

Structure

Transmembrane Region

Constant Region

The constant region of IgM is made up of the two . These heavy chains form a bridge connecting the FAB region or variable region to the transmembrane region (refer to figure 1). They also act as a wire that the variable region can send a signal through to the transmembrane region as a mechanical change.

help hold the heavy chains and Ig Alpha/Beta chains together in the extracellular portion of the transmembrane region.

Variable Region

Relevance