Expression of PD-1 Molecule on Regulatory T Lymphocytes in Patients with Insulin-Dependent Diabetes Mellitus

Author: Perri Valentina   Russo Benedetta   Crinò Antonino   Schiaffini Riccardo   Giorda Ezio   Cappa Marco   Rosado Maria Manuela   Fierabracci Alessandra  

Publisher: MDPI

E-ISSN: 1422-0067|16|9|22584-22605

ISSN: 1422-0067

Source: International Journal of Molecular Sciences, Vol.16, Iss.9, 2015-09, pp. : 22584-22605

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Abstract

Type 1 diabetes is caused by autoreactive T cells that destroy pancreatic beta cells. Animal models suggested that a CD4+CD25+ population has a regulatory function capable of preventing activation and effector functions of autoreactive T cells. However, the role of CD4+CD25high T cells in autoimmunity and their molecular mechanisms remain the subject of investigation. We therefore evaluated T regulatory cell frequencies and their PD-1 expression in the peripheral blood of long-standing diabetics under basal conditions and after CD3/CD28 stimulation. Under basal conditions, the percentages of T regulatory cells were significantly higher while that of T effector cells were significantly lower in patients than in controls. The ratio of regulatory to effector T cells was higher in patients than that in controls, suggesting that T regulatory cells were functional in patients. Percentages of total PD-1+, PD-1low and PD-1high expressing T regulatory cells did not change in patients and in controls. After stimulation, a defect in T regulatory cell proliferation was observed in diabetics and the percentages of total PD-1+, PD-1low and PD-1high expressing cells were lower in patients. Our data suggest a defective activation of T regulatory cells in long-standing diabetics due to a lower expression of PD-1 on their surface.

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