Factors influencing in vitro Lymphocyte transformation for screening immunomodulation drugs among crude herbal extracts

When in vitro lymphocyte transformation test was used to investigate the immunologic effects of crude herbal extracts, false negative results of 3H-TdR uptake usually were obtained due to the high content of impurities, higher concentration of drugs or incomplete harvest of cells. Microscopic examination of cell growth to be additional index proved very useful because of being less interfered by factor mentioned above. Cell growth examination has high reliability, reproducibility, wider range of suitable drug concentration detectable (20-40 micrograms crude extract/well) and high objectivity of being capably examined by several observers for comparison. Therefore both 3H-TdR uptake and cell growth examination should be adopted for indications of this test to obtain accurate objective results. In case of increasing adhesion of cells with surfaces of plate wells by crude herbal extract it is necessary to elevate negative pressure (700 mmHg) and prolong the time of wash-suction (1.5-2 min) during cell harvesting.