RESUMEN
Klebsiella pneumoniae was cultured followed by the preparation and immunoactivity elucidating of its polysaccharide (CPS). The lysis of cell is the first key step in the preparation, under the co-action of trypsin, lysozyme and NP-40, the cell lysed within 2h, then the lysate was concentrated by ultrafiltration which serves as concentrating and partial purifying action simultaneously. Crude CPS was got by ethanol precipitation, then purified through the Ion-exchange and gel filtration, the purity of CPS was judged by the gel filtration and agarose gel electrophoresis. The effect of CPS on the cell immunoactivity was studied in detail, the results show that CPS possesses bidirectional immunoregulation on the spleen cells of mice, that is, low concentration of CPS can stimulate the immune response while the high concentration manifests the inhibition significantly. The investigation results will benefit on the exploitation of the CPS.