Each immunoglobulin molecule consists of two identical heavy chains and two identical light chains. There are two types of light chains designated as kappa and lambda. The kappa light chain antibody labels kappa light chain expressing B lymphocytes and plasma cells. Other cells may also express kappa light chain due to nonspecific uptake of immunoglobulin. Individual B cells express either kappa or lambda light chains. Monoclonality is generally assumed to be evidence of a malignant proliferation. The pairing of an anti-lambda with a kappa light chain antibody is useful for identifying monoclonality of lymphoid malignancies.