Electron microscopic study of endogenous peroxidase activity in human liver macrophages

Abstract

We evaluated the conditions of fixation for ultrastructurally demonstrating the endogenous peroxidase (PO) activity of macrophages in biopsied human liver. The application of microwaving and immersion fixation with tannic acid and aldehydes allowed excellent visualization of PO activity in the nuclear envelope (NE), rough endoplasmic reticulum (rER), and cytoplasmic granules (CG), with good preservation of cellular ultrastructures. The macrophages with PO activity showed one of the following five patterns of PO localization: positive in both the NE and rER but negative in the CG (type 1); negative in both the NE and rER but positive in the CG (type 2); negative in the NE but positive in both the rER and CG (type 3); positive in all three (type 4); PO negative (type 5). The type 1 cells resembled typical Kupffer cells, type 2 cells monocytes, and type 3 and 4 cells the exudate-resident macrophages considered to be a transitional form between exudate and resident macrophages. Type 5 cells may also be a transitional form between the exudate and resident macrophage, or an end-stage macrophage derived from exudate macrophages which have lost their PO activity. Tannic-acid-aldehyde immersion fixation with microwaving may be a useful method in the study of the PO activities of macrophages in biopsied human liver specimens.

Peroxidase Substrates Stimulate the Oxidation of Hydralazine to Metabolites Which Cause Single-Strand Breaks in DNA

“…The toxicological significance to these findings would be primarily dependent upon physiological constraints such as location and pH. Using an electron microscopy technique, it has been shown that endogenous peroxidase activity exists in hepatic macrophage rough endoplasmic reticulum, nuclear envelope, and cytoplasm (29). Prostaglandin H synthase, another type of peroxidase, also resides within the endoplasmic reticulum which is contiguous with the nuclear membrane (30).…”

The immunophenotype of antigen presenting cells of the mononuclear phagocyte system in normal human liver – A systematic review

“…They readily phagocytose latex beads [96] and express a variety of macrophage related scavenger receptor molecules [40,69]. However, there is clearly variability in the expression of these markers and other molecules amongst KCs and light [32] and electron [86] microscopy findings have identified that KCs are composed of differing subsets of cells, which are distributed through different zones of the liver lobule. These findings indicate that KCs appear to be heterogeneous, but exploration of KC subset composition and function is lacking.…”

“…In 1995, Ueda et al [86] described KC functional heterogeneity based on endogenous peroxidase activity that divided the cells into monocytes and four types of macrophages that showed a zonal distribution. These findings suggest that KCs are a collection of cells with varying phenotypes throughout different parts of the healthy liver, which is a concept that has been further supported by work in chronically hepatitis C virus infected livers [16].…”

“…• "Thin"-extended cytoplasm [32] • "Round"-larger cells with round cytoplasm [32] • 5 subsets defined by varying endogenous peroxidase activity and levels of endoplasmic reticulum [86] • Minimal functional experimental evidence on liver macrophages • Liver Macrophages appear to be predominantly tolerogenic in nature, with a regulatory and scavenging role [41,57,69,89] • Function inferred through observations of variable expression of antigen presenting molecules [72], lectins [33,49,55,69,92], Fc Receptors, complement receptors [70], low co-stimulatory marker expression [77] and inhibitory markers such as Z39Ig [89] Perisinusoidal [78] • [101] Tolerogenic in nature • Lower expression of costimulation markers compared to spleen [98] • Produce IL-10 on LPS stimulation [98] • Stimulate T-cells that are IL-10 producing and hypo-responsive on re-stimulation [98] • Produce higher numbers of FoxP3 + Treg cells on naïve T cell stimulation [98] • Weak MLR response compared to blood [98] Portal tract [103] • divided into subsets with different potential for antigen presentation, motility, and cytokine production, all of which can help determine the nature of the immune system's response [17]. A particular complicating factor in the case of the liver is that circulating monocytes also traffic through the sinusoids, and distinguishing between in transit monocyte subsets and other MPS subsets is an evolving science [17].…”