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A. Abedin, A. Hopkinson, M. Mathew, H.S. Dua; Antimicrobial Peptide Expression on the Ocular Surface in Health and Disease . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4967.
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Antimicrobial peptides (AMPs) are the eukaryotic analogues of antibiotics. They have been shown to have both antimicrobial activity and a role as signalling peptides. Human Beta Defensins 1 and 2 ( HBD1 and 2) have been shown to be constitutively expressed on the ocular surface and the latter to be inducible as well. HBD3 has been found in most corneal and conjunctival specimens in previous studies but the nature of this expression has been variable. We studied the expression of a wide range of AMPs on corneal and conjunctival cells of the ocular surface obtained by impression cytology in patients with different ocular surface diseases.
Total RNA was extracted from the cells. This was subjected to reverse transcription Polymerase Chain Reaction (PCR) using primers for 22 AMPs. Results were analysed by means of agarose gel electrophoresis.
The specimens were divided into four groups, controls, dry eye, viral and bacterial infections. Five to ten specimen both corneal and conjunctival in each of these four groups were analysed. HBD1 and 2 were expressed constitutively in most samples. 7 of the other AMPs were found to be present, namely, LEAP2 , LEAP1, LL37, 118 and 122.. There appeared to be no significant changes in the expression of these AMPs between the groups. Though the RNA yield was much poorer from corneal as compared to conjunctival samples all samples yielded good amounts of good quality DNA as confirmed by spectrophotometry. There did not appear to be significant differences between the corneal and conjunctival samples.
There were no qualitative differences in AMP expression between the different disease states. Most AMPs detected at the ocular surface appear to be constitutively expressed. They are more likely to have a role as signalling peptides rather than directly as antimicrobials. The fact that there are a large number of AMPs which have diverse activities and act synergistically may explain the fact that we did not find an upregulation of HBD3 in ocular inflammation as has been documented in a previous study.
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