Objective: To investigate the levels of NK cells and their relevant cytokines (IL-10, TGF-β and IFN-γ) in patients with primary immune thrombocytopenia (ITP) .

Methods: All samples were obtained from 42 patients (22 newly diagnosed and 20 in remission) and 20 healthy volunteers. The levels of IL-10 and IFN-γ in blood serum were detected by enzyme-linked immunosorbent assay (ELISA) . The percentage of CD3(-) CD56(+) NK cell, CD3(-) CD56(bright) CD16(-) NK cell, CD3(-) CD56(dim) CD16(+) NK cell in peripheral blood lymphocyte were detected by flow cytometry. The NK cells were isolated by immunomagnetic microbeads. The mRNA expression levels of IL-10, TGF-β, and IFN-γ in NK cells were detected by real-time fluorescent quantitative PCR. Correlation between the above measured results was analyzed.

Results: ① The blood serum level of IFN-γ in newly diagnosed ITP patients [ (653.0±221.6) ng/L] was higher than that in remission ITP patients [ (484.4±219.5) ng/L] and healthy control [ (390.9±253.5) ng/L] (P=0.022, P=0.001) . The blood serum level of IL-10 in newly diagnosed ITP patients was lower than that in healthy control [ (52.09±26.66) ng/L vs (79.44±38.43) ng/L, P=0.007]. ②The percentage of NK cell in newly diagnosed and remission ITP patients [ (9.53±3.93) %, (9.03±3.78) %] were significantly lower than that in healthy control [ (13.72±7.42) %] (P=0.013, P=0.007) . The ratio of CD3(-) CD56(bright) CD16(-) NK cell/total NK cells in newly diagnosed ITP patients was higher than that in healthy control [ (6.85±4.43) % vs (4.05±2.81) %, P=0.032]. The ratio of CD3(-)CD56(dim) CD16(-) NK cell/total NK cells in newly diagnosed ITP patients was lower than that in healthy control [ (93.14±4.43) % vs (95.94±2.81) %, P=0.032]. ③ There was no significant difference in the mRNA expression level of IFN-γ in NK cells of ITP patients and healthy control (all P>0.05) . The mRNA expression levels of IL-10 and TGF-β in NK cells in newly diagnosed ITP patients were significantly higher than that in healthy control (1.82±1.32 vs 1.02±1.03, P=0.023; 2.80±2.31 vs 1.46±1.37, P=0.028) . The ratio of CD3(-)CD56(bright) CD16(-) NK cell/total NK cells was positively correlated with the mRNA expression levels of IL-10, TGF-β in NK cells (r=0.424, P=0.001; r=0.432, P<0.001) .

Conclusion: NK cells may compensate for the deficiency of the number by enhancing the secretion of negative regulation cytokines, acting as "protective" roles in the disease.