Tear N-glycomics in vernal and atopic keratoconjunctivitis

Allergy. 2021 Aug;76(8):2500-2509. doi: 10.1111/all.14775. Epub 2021 Mar 15.


Purpose: Tear fluid N-Glycome from patients affected with vernal (VKC) and atopic keratoconjunctivitis (AKC) was investigated to identify specific changes in tears and to recognize possible glyco-biomarkers.

Methods: The analysis of the N-glycans was performed using matrix-assisted laser desorption ionization mass spectrometry on single tear samples. Tears from control normal subjects (CTRL), VKC and AKC patients were processed and treated with peptide N-glycosidase F (PNGase F) to deglycosylate N-glycoproteins. Released N-glycans were purified, permethylated, and analyzed by matrix-assisted laser desorption/ionization-time of flight mass spectrometry and tandem mass spectrometry (MALDI-TOF MS and MALDI-TOF MS/MS).

Results: More than 150 complex N-glycans, including highly fucosylated biantennary, triantennary, tetra-antennary, and bisecting species, were observed in our spectra. Three distinct patterns for CTRL, VKC, and AKC patients were identified in terms of relative intensities for some N-glycans structures. Major variations involved bisecting and hyperfucosylated glycoforms. The most intense ions were associated with species at m/z 1907.0 (asialo, agalacto, bisected, biantennary structure-NGA2B) in CTRL MS profiles, at m/z 2605.3 and 2966.5 in VKC, and at m/z 2792.4 in AKC corresponding to a well-known biantennary, disialylated N-glycan. Several peaks were associated with structures bearing one or two Lewis X epitopes. Structures were confirmed by MS/MS analysis. Quantitative differences among the three groups were statistically significant.

Conclusions: Tear MS profiles are rich in specific glycoforms, particularly those with a high fucosylation degree, indicating both core and peripheral decoration. Tear N-glycome analysis provided important information for a better comprehension of VKC and AKC alterations at the molecular level.

Keywords: atopic keratoconjunctivitis; glycomics; mass spectrometry; tears; vernal keratocojunctivitis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Conjunctivitis, Allergic* / diagnosis
  • Glycomics
  • Humans
  • Keratoconjunctivitis*
  • Polysaccharides
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Tandem Mass Spectrometry
  • Tears


  • Polysaccharides