Immunoglobulins are the antigen recognition molecules of B cells. An Immunoglobulins molecule is made up of 2 identical heavy chains and 2 identical light chains joined by disulfide bonds so that each heavy chain is linked to a light chain and the 2 heavy chains are linked together. On each of the light chains, there is one variable region and a constant region. The variable region is the most important for binding to antigens.