Expression of costimulatory molecule inducible costimulator and coinhibitory molecule programmed death-1 in patients with myasthenia gravis

Abstract

Objective To explore the immunopathological mechanism for the imbalance between the positive signal mediated by inducible costimulator (ICOS) and the negative signal mediated by programmed death-1 (PD-1) in patients with myasthenia gravis (MG). Methods Eighty-two patients with MG, 56 healthy controls (HC) and 20 non-MG (NMG) patients, collected in the First Affiliated Hospital of Suzhou University from February 2014 to December 2016, were chosen to participate in the study. The expression of ICOS and PD-1 on peripheral blood mononuclear cells was detected by immuno-fluorescence staining and flow cytometry. The levels of soluble programmed death-1 (sPD-1), soluble programmed death ligand 1 (sPD-L1), IL-4 and other cytokines were detected by enzyme-linked immunosorbent assay. Results (1) Flow cytometry analysis: The co-expression of PD-1, ICOS on CD4+ T cells from MG group (9.64%(8.82%)) was higher than in HC (1.81%(2.10%), Z=-7.389, P<0.05) and NMG group (2.86%(1.49%), Z=-4.636, P<0.05). The expression of ICOS on CD4+ T cells, ICOS ligand (ICOSL) on CD14+ monocytes and CD19+ B cells were increased in MG group comparing with that of the control groups. The proportion of PD-1+ CD4+ T cells (MG group 16.82%(10.66%), HC 9.34%(9.18%), Z=-4.345, P<0.05; NMG group 7.07%(3.40%), Z=-4.594, P<0.05) and PD-1 Ligand (PD-L1)+ CD14+ monocytes was higher in MG patients. All of these were detected by flow cytometry. (2) ELISA analysis: Serum sPD-1 expression significantly increased in MG group compared with that in the control groups (MG group (1.87±0.64) ng/ml, NMG group (1.49±0.70) ng/ml, t=2.04, P<0.05; HC (1.05±0.50) ng/ml, t=2.08, P<0.05), while for serum sPD-L1, there was no significant difference between MG and control groups. (3)Serum cytokines detection: The expression of IL-4 was increased in MG patients (MG group (61.88±5.15) pg/ml, HC (32.03±1.84) pg/ml, t=2.50, P<0.05; NMG group (42.62±3.31) pg/ml, t=2.34, P<0.05), and there was a negative correlation between the expression of sPD-1 and the concentration of IL-4. Conclusions The increased expression of PD-1+ ICOS+ CD4+ T cells suggested the subset involved in the pathological progress of MG. sPD-1 might disturb the ligation of PD-1 on T cells and PD-L1 on antigen presenting cells, while the ligation of ICOS and ICOSL passed positive signal, leading to over activity of the subsets and the progression of disease. Key words: Myasthenia gravis; Cytokines; Flow cytometry; Inducible costimulator; Programmed death-1