Immunoglobulin classes share the same basic four polypeptide chain structure of two heavy chains (five types) and two light chains (kappa, lambda; both having a molecular weight of 22.5 kDa). Kappa and lambda consist of a variable region and a constant region and can easily be differentiated by the antigenic properties of the constant region. The ratio of kappa to lambda is 70:30. Antibodies to the kappa light chain are reportedly useful in the identification of leukemias, plasmacytomas, and certain non-Hodgkin's lymphomas. Demonstration of clonality in lymphoid infiltrates indicates that the infiltrate is clonal and therefore malignant.