The heavy chains of the immunoglobulins are denoted by the Greek letters i.e IgG is known as the gamma-chain. In normal serum, IgG is the major immunoglobulin class constituting about 75% of the total immunoglobulin. The normal B-cell population is polyclonal and expresses a range of different immunoglobulin molecules. In contrast, a majority of B-cell neoplasias are characterized by the proliferation of monoclonal cells expressing only one type of light chain, but still having a diversity in the heavy chain size and composition. This distinct expression of immunoglobulins by proliferating monoclonal B-cells makes antibodies specific for immunoglobulin light- and heavy chains useful for the classification of these neoplasias.