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K. C. McKenna, K. M. Beatty, A. D. Singh; Uveal Melanoma Patients With Increased Percentages of CD11b+ CD15+ Myeloid Derived Suppressor Cells in Blood Demonstrate Impaired T Cell Function. Invest. Ophthalmol. Vis. Sci. 2010;51(13):843.
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© ARVO (1962-2015); The Authors (2016-present)
To determine whether expansion of CD11b+ CD15+ myeloid derived suppressor cells (MDSC) in the blood of uveal melanoma (UM) patients was associated with impaired T cell function
Blood was collected in CPT tubes with heparin (Becton Dickinson) from patients with a clinical diagnosis of UM (9 female, 9 male, aged 42-89) before surgery and in follow-up visits, and from healthy control donors (28 female, 26 male, aged 50-69). PBMC were isolated by centrifugation within 3 hours and then stored at room temperature in autologous plasma for 1-4 days. Flow cytometry was performed to evaluate expression of CD68 and CD15 on CD11b+ cells. CD11b+ cells were isolated from PBMC by magnetic cell separation and then PBMC with and without CD11b+ cells were labeled with CFSE and stimulated with PHA or anti-CD3/CD2/CD28 beads. Four days later proliferation of PBMC was determined by flow cytometric analysis of CFSE dilution.
Four UM patients demonstrated increased percentages of CD11b+ cells in PBMC (72.2%, 48.8%, 49.6%, 46.3% of total PBMC) that were two standard deviation greater than observed in healthy control donors (mean+/- standard deviation = 30 +/- 7.8 % of total PBMC). The percentage of CD11b+ cells that coexpressed CD15 in these patients was also elevated (48.3%, 31.5%, 21.4%, 26.7% of total PBMC) in comparison to healthy controls (median 4.4%, range= 1.09 -24.4% of total PBMC). In one of these UM patients, the percentage of T cells that had proliferated following mitogen stimulation (22%) was reduced two-fold in comparison to an age matched healthy control donor (43%). In another patient T cell proliferation within PBMC increased when CD11b+ cells were removed.
Activated CD11b+ CD15+ granulocytes increased in certain UM patients reproducing our previously published results (McKenna, K. C. et al. 2009. Invest. Ophthalmol. Vis. Sci. 50:4295). T cell function was impaired by these granulocytes suggesting that they are myeloid derived suppressor cells which may contribute to UM progression by inhibiting tumor-specific T cell responses.
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