Characterising the association of latency with α(1)-antitrypsin polymerisation using a novel monoclonal antibody.
Bottom Line: Polymers are retained within the hepatocyte endoplasmic reticulum (ER) in homozygous (PiZZ) individuals, predisposing the individuals to hepatic cirrhosis and emphysema.In vitro kinetics analysis showed polymerisation dominated the pathway but latency could be promoted by stabilising monomeric α1-antitrypsin.Polymers were extensively produced in hepatocytes and a cell line expressing Z α1-antitrypsin but the latent protein was not detected despite manipulation of the secretory pathway.
Affiliation: Department of Medicine, University of Cambridge, Cambridge Institute for Medical Research, Cambridge, UK; Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.Show MeSH
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Mentions: Liver tissue samples from 30 individuals with five different α1-antitrypsin genotypes (Table 1) and two PiMM control samples were analysed by immunohistochemistry and confocal microscopy. None of these individuals were receiving α1-antitrypsin augmentation therapy. The staining showed that polymers were most commonly located in the periportal zone in close proximity to portal tract fibrous tissue, forming ring-like patterns (Fig. 5A). High power images revealed that hepatocytes containing the greatest concentration of polymers were almost always in close proximity to fibroblasts. Whilst polymer was detected in tissue samples from all individuals who were homozygous or heterozygous for the Z allele (Table 1), only five individuals (all PiZZ) showed positive signals for latent α1-antitrypsin. The latent signals, if present, were only found in PiZZ individuals with advanced liver fibrosis. Comparing the signal intensity and distribution, the latent signals were much more sparse than the polymer signals, as observed in the HRP–DAB staining of serial tissue slides (Fig. 5B). In confocal microscopy, co-localisation of the conformer-specific (polymeric or latent) signal was assessed with the non-selective signal of total α1-antitrypsin stained by a rabbit polyclonal antibody (Fig. 5C).
Affiliation: Department of Medicine, University of Cambridge, Cambridge Institute for Medical Research, Cambridge, UK; Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.