Retinal pigment epithelium and microglia express the CD5 antigen-like protein, a novel autoantigen in age-related macular degeneration

Alessandro Iannaccone, T. J. Hollingsworth, Diwa Koirala, David D. New, Nataliya I. Lenchik, Sarka Beranova, Ivan Gerling, Marko Radic, Francesco Giorgianni

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

We report on a novel autoantigen expressed in human macular tissues, identified following an initial Western blot (WB)-based screening of sera from subjects with age-related macular degeneration (AMD) for circulating auto-antibodies (AAbs) recognizing macular antigens. Immunoprecipitation, 2D-gel electrophoresis (2D-GE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), direct enzyme-linked immunosorbent assays (ELISA), WBs, immunohistochemistry (IHC), human primary and ARPE-19 immortalized cell cultures were used to characterize this novel antigen. An approximately 40-kDa autoantigen in AMD was identified as the scavenger receptor CD5 antigen-like protein (CD5L), also known as apoptosis inhibitor of macrophage (AIM). CD5L/AIM was localized to human RPE by IHC and WB methods and to retinal microglial cells by IHC. ELISAs with recombinant CD5L/AIM on a subset of AMD sera showed a nearly 2-fold higher anti-CD5L/AIM reactivity in AMD vs. Control sera (p = 0.000007). Reactivity ≥0.4 was associated with 18-fold higher odds of having AMD (χ2 = 21.42, p = 0.00063). Circulating CD5L/AIM levels were also nearly 2-fold higher in AMD sera compared to controls (p = 0.0052). The discovery of CD5L/AIM expression in the RPE and in retinal microglial cells adds to the known immunomodulatory roles of these cells in the retina. The discovery of AAbs recognizing CD5L/AIM identifies a possible novel disease biomarker and suggest a potential role for CD5L/AIM in the pathogenesis of AMD in situ. The possible mechanisms via which anti-CD5L/AIM AAbs may contribute to AMD pathogenesis are discussed. In particular, since CD5L is known to stimulate autophagy and to participate in oxidized LDL uptake in macrophages, we propose that anti-CD5L/AIM auto-antibodies may play a role in drusen biogenesis and inflammatory RPE damage in AMD.

Original languageEnglish (US)
Pages (from-to)64-74
Number of pages11
JournalExperimental Eye Research
Volume155
DOIs
StatePublished - Feb 1 2017

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CD5 Antigens
Retinal Pigment Epithelium
Autoantigens
Macular Degeneration
Microglia
Macrophages
Apoptosis
Proteins
Antibodies
Immunohistochemistry
Serum
Western Blotting
Enzyme-Linked Immunosorbent Assay
Antigens
Scavenger Receptors
Autophagy
Electrophoresis, Gel, Two-Dimensional
Tandem Mass Spectrometry
Immunoprecipitation
Liquid Chromatography

All Science Journal Classification (ASJC) codes

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

Cite this

Retinal pigment epithelium and microglia express the CD5 antigen-like protein, a novel autoantigen in age-related macular degeneration. / Iannaccone, Alessandro; Hollingsworth, T. J.; Koirala, Diwa; New, David D.; Lenchik, Nataliya I.; Beranova, Sarka; Gerling, Ivan; Radic, Marko; Giorgianni, Francesco.

In: Experimental Eye Research, Vol. 155, 01.02.2017, p. 64-74.

Research output: Contribution to journalArticle

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abstract = "We report on a novel autoantigen expressed in human macular tissues, identified following an initial Western blot (WB)-based screening of sera from subjects with age-related macular degeneration (AMD) for circulating auto-antibodies (AAbs) recognizing macular antigens. Immunoprecipitation, 2D-gel electrophoresis (2D-GE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), direct enzyme-linked immunosorbent assays (ELISA), WBs, immunohistochemistry (IHC), human primary and ARPE-19 immortalized cell cultures were used to characterize this novel antigen. An approximately 40-kDa autoantigen in AMD was identified as the scavenger receptor CD5 antigen-like protein (CD5L), also known as apoptosis inhibitor of macrophage (AIM). CD5L/AIM was localized to human RPE by IHC and WB methods and to retinal microglial cells by IHC. ELISAs with recombinant CD5L/AIM on a subset of AMD sera showed a nearly 2-fold higher anti-CD5L/AIM reactivity in AMD vs. Control sera (p = 0.000007). Reactivity ≥0.4 was associated with 18-fold higher odds of having AMD (χ2 = 21.42, p = 0.00063). Circulating CD5L/AIM levels were also nearly 2-fold higher in AMD sera compared to controls (p = 0.0052). The discovery of CD5L/AIM expression in the RPE and in retinal microglial cells adds to the known immunomodulatory roles of these cells in the retina. The discovery of AAbs recognizing CD5L/AIM identifies a possible novel disease biomarker and suggest a potential role for CD5L/AIM in the pathogenesis of AMD in situ. The possible mechanisms via which anti-CD5L/AIM AAbs may contribute to AMD pathogenesis are discussed. In particular, since CD5L is known to stimulate autophagy and to participate in oxidized LDL uptake in macrophages, we propose that anti-CD5L/AIM auto-antibodies may play a role in drusen biogenesis and inflammatory RPE damage in AMD.",
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AU - Iannaccone, Alessandro

AU - Hollingsworth, T. J.

AU - Koirala, Diwa

AU - New, David D.

AU - Lenchik, Nataliya I.

AU - Beranova, Sarka

AU - Gerling, Ivan

AU - Radic, Marko

AU - Giorgianni, Francesco

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