UP-REGULATION OF PHAGOCYTOSIS AND CANDIDICIDAL ACTIVITY OF MACROPHAGES EXPOSED TO THE IMMUNOSTIMULANT, ACEMANNAN

Previous studies by these investigators have shown that mannosylated b ovine serum albumin (mBSA) enhances the respiratory burst (RB), phagoc ytosis, and killing of Candida albicans by resident murine peritoneal macrophages (MO). Upregulation of the above MO functions was associate d with binding of mBSA to the MO-mannose receptor. The present study w as done to determine if the immunostimulant, acemannan prepared from a loe vera, could stimulate MM in a similar manner. Resident peritoneal MO collected from C57BL/6 mice were exposed to acemannan for 10 min. T he RB was measured using chemiluminescence and demonstrated approximat ely a two-fold increase above the media controls. In studies involving phagocytosis, MO were exposed to acemannan, washed and exposed to Can dida at a ratio of 1:5. The percent phagocytosis and Candida killing w ere determined using fluorescence microscopy. There was a marked incre ase in phagocytosis in the treated cultures (45%) compared to controls (25%). Macrophages exposed to acemannan for 10 min resulted in ca 38% killing of Candida albicans compared with 0-5% killing in controls. I f MO were incubated with acemannan for 60 min, 98% of the yeast were k illed compared to 0-5% in the controls. The results of the present stu dy indicate that short term exposure of MO to acemannan upregulates th e RB, phagocytosis and candidicidal activity. Further studies are need ed to clarify the potential use of this immunostimulant as an anti-fun gal agent. (C) 1997 International Society for Immunopharmacology.