Table 1.
Potential ocular allergy biomarkers identified by previous studies and their associated functions.
| Ocular Allergy Protein Biomarker | Function | Change in Concentration (Ocular Allergy versus Healthy Controls) | Analytical Technique |
|---|---|---|---|
| Alpha defensin | Defensins have been shown to be antimicrobial and are able to speed up epithelial tissue healing [42] | Increased [56] | ELISA [56] |
| Beta-2 microglobulin | Produced by T and B cells, beta-2 microglobulin forms part of the HLA † class I molecule and has been linked to a number of inflammatory disorders [51,72] | Increased [51] | Mass spectrometry [51] |
| Deleted in malignant brain tumours 1 protein | Contributes to innate immune reaction control [73] | Decreased [51] | Mass spectrometry [51] |
| Eosinophil cationic protein | Mast cell degranulation and neutrophil activation [66,68] | Increased [3,57] | Radioimmunoassay [3] Enzyme-linked immunosorbent assay (ELISA) [57] |
| Eosinophil major basic protein | Mast cell degranulation and immunoregulatory roles [68] | Increased [3,57,66,67,68] | Radioimmunoassay [3] Enzyme-linked immunosorbent assay (ELISA) [57] Concentration-dependent chemiluminescence assay [66] Radioimmunoassay [67] |
| Eosinophil neurotoxin | Potential inflammatory role [67] | Increased [3,57] | Radioimmunoassay [3] Enzyme-linked immunosorbent assay (ELISA) [57] |
| Ig ‡ light chains | Building block of various immunoglobulins, suggests an increase in Ig ‡ A or Ig ‡ E production in response to allergy [53,69,74] | Decreased [51] Increased [53] |
Mass spectrometry [51] AET [53] |
| Ig ‡ G Ig ‡ gamma-2 heavy chain C region | Primarily involved in homeostasis and protection [75] | Increased [51] | Mass spectrometry [51] |
| IgA | Antimicrobial activity and host defence [62] | Increased [40] | AET [40] |
| Lactoferrin | Immunomodulatory and antimicrobial when coupled with lysozyme C [60] | Increased [40,53] | AET [40,53] |
| Leukocyte elastase inhibitor | Anti-apoptotic effects when associated with DNase II [76]. Controls effects of proteinase 3, an enzyme that triggers cell signalling and inflammation [76,77] | Increased [55] | Sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blot [55] |
| Lipocalin-1 | Binds to and regulates lipid distribution on the ocular surface [65] | Increased [51] Decreased [53] |
Mass spectrometry [51] AET [53] |
| Lysozyme C | Antimicrobial activity and host defence [60] | Decreased [53] | AET [53] |
| Prolactin-Induced Protein | Plays a role in immune modulation and host defence [61] | Increased [51] | Mass spectrometry [51] |
| Secretoglobulin Family 1D member 1 | Secretoglobins are produced by the lacrimal gland of the eye and are involved in binding lipids to help build and maintain the lipid layer of the tear film [43] | Increased [51] | Mass spectrometry [51] |
| ZAG | Not yet been characterised (though has been suggested to be immune-related) [64] | Increased [51] Decreased [53] |
Mass spectrometry [51] AET [53] |
| Zymogen granule protein 16 homolog B | Unknown, though potentially plays a protective role on the ocular surface [78] | Decreased [51] | Mass spectrometry [51] |
† HLA—human leukocyte antigen complex, ‡ Ig—immunoglobulin.