Kappa light chains of human immunoglobulins occur in 50-70 % of normal human B lymphocytes while lambda light chains are expressed in 30-50 % of these cells. Abnormal expression of kappa and lambda light chains occur in leukemia. Anti-kappa and anti-lambda antibodies are frequently used in combination with CD19 or CD138 for the detection of light chains of surface immunoglobulin on normal and neoplastic B cells.