Five isolectins, L-4, L3E1, L2E2, L1E3 and E-4, were purified from red kidney bean (Phaseolus vulgaris) by affinity chromatography on a porcine thyroglobulin bound Sepharose(R) 4B column, and subsequent separation by Sulfopropyl Sephadex C-50 ion exchange chromatography. Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SIDS-PAGE), one clear band appeared for each isolectin, which confirmed the high purity. The decreased haemagglutination activity in an order of E-4, L1E3, L2E2, L3E1 and L-4 further proved the high separation efficiency of the two columns. Low concentration (1 mu g/mL) of E-4 was able to stimulate the proliferation of human H9 lymphoma cells but strong cytotoxicity was observed at higher concentration. The H9 cell viability was inhibited by the five isolectins in a dose-dependent manner. The concentrations that inhibited 50% of the H9 cell viability were determined to be 3.385 mu M for L4, 7.778 mu M for L3E1, 9.939 mu M for L2E2, 20.840 mu M for L1E3 and 33.004 mu M for E-4, respectively. L-4 showed more potent cytotoxicity than E-4, which was probably due to stronger binding of L-4 with the cell-surface carbohydrates than E-4. It may also be due to the partial masking of E-4 cytotoxicity by the glycoprotein supplemented in the medium. (C) 2008 Elsevier B.V. All rights reserved.