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S. E. Coupland, S. Spieckermann, H. Stein, C. Loddenkemper; FOXP3+ Regulatory T-Cells (Tregs) in Conjunctival Naevi and Conjunctival Melanoma. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4798.
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It is generally accepted that regulatory T cells (Treg CD4+CD25highFoxp3+) play an important role in the suppression of anti-tumour immunity and may mediate tolerance to tumour associated antigens. Very little is known about the immunology of conjunctival melanoma. An inflammatory reaction comprising T cells and macrophages has been noted in conjunctival melanoma. We immunostained conjunctival biopsies from patients with conjunctival naevi and melanoma to investigate the frequency of Tregs in these tumors, to determine whether these cells may play a role in the immune response in conjunctival melanomas.
Biopsies of conjunctival naevi (n=23), conjunctival melanoma (n=15) and normal conjunctiva (n=7) taken from 45 patients (M:F=26:19; age range 5-82 years) were studied. 4 micron sections of formalin-fixed, paraffin-embedded tissue were stained separately with hematoxylin and eosin, and by an indirect immunohistochemical method, using monoclonal antibodies to CD3, CD4, CD8 and the forkhead box transcription factor, FOXP3. Negative control sections were stained with rabbit IgG or irrelevant mouse monoclonal antibody. Antigen retrieval was achieved by boiling sections for 10 minutes in citrate buffer (pH 6.0). Positive cells were quantified per high power field (hpf = 0.237 mm2) within the tumours and in the adjacent stroma;10 hpf were counted in each case.
Normal conjunctiva contained a mean value of 45.5, 28.3, 17.3 and 1.0/10hpf stromal and 21.9, 4.1, 17.3 and 0.7/10hpf intraepithelial CD3, CD4, CD8 and FOXP3 positive T cells, respectively. For conjunctival naevi, the numbers were 282.7, 153.4, 129.2 and 12.2/10hpf in the stroma and 30.4, 8.4, 22.5 and 3.4/10hpf intratumoral for CD3, CD4, CD8 and FOXP3 positive cells, respectively. This compared to 324.3, 215.1, 108.8 and 43.5/10hpf in the stroma and 110.7, 51.4, 59.4 and 24.2 intratumoral for CD3, CD4, CD8 and FOXP3 positive cells, respectively in the conjunctival melanomas. Thus, compared to conjunctival naevi, there was a significant increase in the number of Tregs in conjunctival melanomas in both the tumour tissue (p<0.001) and surrounding stroma (p=0.003).
Conjunctival melanomas are associated with an increase in FOXP3+ Tregs compared to benign naevi. It remains to be determined whether these cells have a relevance in the progression, recurrence or dissemination of these tumours. An inhibition or depletion of Tregs may be considered in the armentarium of conjunctival melanoma immunotherapy.
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