The molecular weight (MW) of pectic polysaccharide АА3 equal to 150 kDa and its structure suggest that it has a non-permeating protector action.To study the ability of low methylesterified galacturonan АА3, extracted from Aloe arborescens Mill., to influence the cryoprotective properties of the refrigerant in the cryopreservation of leukocytes (-20°С, -80°С).Pectic polysaccharide АА3 was extracted from fresh leaves using a 0.7% (w/w) solution of ammonium oxalate. The cryoscopic method was used to study its ability in different concentrations (0.1-1% w/v) in a mixture with glycerol to change the osmolarity and freezing temperature of the venous blood. Venous blood was protected with a comprehensive cryopreservative solution (3.5 % glycerol + 0.1 % pectic polysaccharide АА3) and stored at -20°C and -80°C for 1 and 7 days.The cryoprotective properties of glycerol solution (3.5%) containing AA3 at 0.1 to 1.0% led to a decrease in the osmolarity of venous blood and accelerated the process of water freezing. So, these solutions act as nucleators. A solution of AA3 (0.1%) and glycerol (3.5%) improves the morphological preservation of granulocytes, resistance of cell membranes to eosin and phagocytic activity of neutrophils after -20°C storage for 7 days.The addition to glycerol solution (3.5%) of pectic polysaccharide АА3 (0.1%) may facilitate the formation of a three-dimensional network of intermolecular hydrogen bonds between the functional groups of pectin (mainly carboxyl) and hydroxyl groups of polyhydric alcohol. Better linkage of cellular water molecules in the biological specimen may improve cryoprotection.