Effect of lactoferrin on the phagocytic activity of polymorphonuclear leucocytes isolated from blood of patients with autoimmune diseases and Staphylococcus aureus allergy.

Phagocytic number (PN) and phagocytic index (PI) of neutrophils isolated from blood of patients with autoimmune diseases, allergy to Staphylococcus aureus and from blood of healthy individuals were examined. Our results concerning the influence of lactoferrin (Lf); (6.7 mg/l) on the PI of PMN showed that: 1) Lf enhances reliable PI of PMN at the 30-th minute starting the phagocytic reaction in patients with autoimmune disease in an active stage, in blood donors treated as healthy with the presence of autoantibodies, in patients with autoimmune diseases and proved autoantibodies against tissue, cell antigens and collagen, 2) Lf influences non-significantly PI of PMN in patients with autoimmune collagen diseases in remission, 3) Lf increases PI of PMN with 19% only in 58% from the assessed patients with Staphylococcus aureus, and 4) Lf decreases non-significantly PI of PMN in the healthy controls. Our studies on the effect of Lf on the phagocytic activity of PMN suggest that Lf has stronger effect on the PN compared to the PI: 1) Lf enhances with 86% the PN in patients with Staphylococcus aureus, 2) Lf increases PN of PMN in all of the assessed patients with autoimmune collagen diseases in active stage (mean with 72%), and 3) Lf increases PN of PMN in 4 from the 5 investigated healthy controls (mean with 22%). Our results show a "corrective" effect of Lf on the phagocytic functions in the investigated groups of patients. The possible mechanisms, by which Lf increases PN and PI of neutrophils, is discussed: 1) they may concern the antioxidative properties of Lf to block the iron ions in their catalytic inactive form or to take part as ferric-Lf in an oxidative-reduction processes on the plasma membrane and controlling transmembrane transport systems, 2) Lf decreases the negative surface charge and thus enhances the adherent ability of the PMN. Probably to this stimulated adherent ability dues the increased ingestion of bacteria in the presence of Lf, and 3) The "changed" membrane of PMN may have higher number receptors for Lf to bind more molecules of exogenous Lf. The increase of Lf binding which enhances the adherence and aggregation of neutrophils, facilitates the phagocytosis.