EFFECT OF COMPLEMENT AND OF THE CARBOHYDRATE COMPONENTS OF SPUTUM ON PHAGOCYTOSIS BY HUMAN POLYMORPHONUCLEAR LEUCOCYTES

Abstract

The phagocytic activity of human polymorphonuclear leucocyte preparations, which were free from plasma, has been estimated by direct determination under phase contrast of the number of living cells containing test particles. Spores of Aspergillus fumigatus were phagocytosed in the absence of added serum but phagocytosis of paraffin wax particles occurred only in the presence of serum containing the heat-labile and C′₄ components of complement. In view of the unreactive nature of the paraffin hydrocarbons, it was considered unlikely that natural antibody played any part in the phenomenon.

Although no phagocytosis of wax particles occurred in the absence of serum, almost 100 per cent of cells were phagocytic in preparations containing adequate concentrations of serum. It was therefore possible to determine the serum concentration necessary for 50 per cent of the polymorphs to phagocytose wax particles. By this means it was demonstrated that the addition of the carbohydrate components of sputum had a small but significant inhibitory effect on phagocytosis and that dextran had no such effect. The sputum mucoprotein depressed the complement titre of serum and this might have accounted for the reduction in the ability of a serum to promote phagocytosis when this complex was added. The sputum mucopolysaccharide had no such effect on the complement titre of serum and must have exerted its inhibitory action in some other way.