In Vitro Control of Neutrophilic Phagocytosis of IgG-Coated SRBC by Macromolecules Involved in Released Products From Platelets

Abstract

Analysis of macromolecular fraction of platelet release products (PRPr) was undertaken after we observed that pretreatment of human neutrophils with macromolecules (greater than 10(5) daltons) involved in PRPr enhanced phagocytosis of IgG-sensitized sheep red blood cells (IgG-SRBC). Sephadex G-200 gel filtration of PRPr revealed two macromolecular activators and two suppressors of neutrophilic phagocytosis of IgG-SRBC: MAPP(s), macromolecular activator(s) of phagocytosis from platelets; MSPP(s) macromolecular suppressor(s) of phagocytosis from platelets. The estimated molecular weights of the respective MAPPs were 100 kdaltons to 140 kdaltons (kd) (s-MAPP) and 200 kd to 290 kd (I-MAPP) and those of the respective MSPPs were 60 kd to 100 kd (s-MSPP) and 400 kd to 500 kd (I-MSPP). It is suggested that an I-MAPP molecule has at least an s-MAPP molecule as a functional unit and that MAPPs and larger MSPP (I-MSPP) might be glycoproteins, while smaller MSPP (s-MSPP) seems to contain neither carbohydrates nor lipids. As far as the effects of serum and plasma on phagocytosis of IgG-SRBC by neutrophils are concerned, the serum gave twice as much phagocytic activity as the plasma. Substantial MAPP-like activities were observed in the serum and MSPP-like activities were observed in both the serum and plasma.

Effects of platelet release products on neutrophilic Fcγ receptors

“…L-MAPP and s-MAPP are glycoproteins of 300 and 150 kDa, respectively [10], and it has been shown that they have dimer and tetramer transferrin as constituents [11]. After this observation, l-MAPPand s-MAPP-rich materials produced by conventional gelfiltration method were further refined by affinity chromatography with the use of an anti-transferrin column in this experiment.…”

“…It has been reported that platelet release products (PRPr) involve several substances that enhance human leukocytic phagocytosis [7,8]. We have reported that macromolecular activators of phagocytosis from platelets (MAPP: l-MAPP, 300 kDa; s-MAPP, 150 kDa) in PRPr are activators of phagocytosis of IgG antibody-sensitized particles through Fc␥ receptors [9,10] and are produced from dimers and tetramers of transferrin (TF) in platelets [11].…”

Phagocytosis: An Overview

“…For phagocytosis of IgG-coated Es by neutrophils, those treated with serum give twice as much phagocytic activity compared to those treated with plasma. Considerable amounts of MAPP-like activities have been observed in the serum whereas MSPP-like activities have been observed in serum as well as in plasma [190].…”

An Apolipoprotein CIII-Derived Peptide, Hatktak, Activates Macromolecular Activators of Phagocytosis from Platelets (MAPPs)

“…MAPPs have two subsets, l-MAPP (3x10 5 Da) and s-MAPP (1.5x10 5 Da) [24,25]. Platelets stored in the form of platelet-rich plasma lose the capacity to release MAPPs but recover it if incubated with the plasma-derived precursors of MAPPs (precursors of l-MAPP and s-MAPP, 3x10 5 Da and 1.5x10 5 Da, respectively) and thrombin in the presence of Ca ++ [26].…”