The frequency, phenotypes and in vitro cytotoxic effects of circulating CD56＋ T cells in the patients with chronic HCV infection
Objective To explore the cell frequency, phenotypes and in vitro cytotoxic effects of circulating CD56＋ T ceils in the patients with chronic HCV infection. Methods Peripheral blood mononu- clear cells （PBMCs） were isolated from 33 patients with HCV chronic infection and 21 healthy subjects. Multi-color flow eytometry was used to analyze cell frequency, expressions of activating receptors （ NKG2C, CD16 and NKp46） and inhibitory receptors （NKG2A and CD158a） on CD56＋ T ceils. The functional mark- er for cytotoxic effects （CD107a） on circulating CD56＋ T cells and their cytokines expression （ IFN-γ and TNF-α） with or without stimulation of K562 human Leukemia cell line were also analyzed. Then the correla- tions among the expressing levels of CD107a, IFN-γ and TNF-αwere investigated. Results The frequency of CD56＋ T ceils in periphery lymphocytes were significantly decreased in the patients with chronic HCV in- fection as compared with that in healthy controls （ P = 0. 018 ）. The expressions of activating receptors （NKG2C, CD16 and NKp46） on CD56＋ T cells from HCV infected patients were decreased （P=0. 015 for NKG2C, P=0.036 for CD16 and P=0.001 for NKp46）, while there was no significant change in the ex- pressions of inhibitory receptors （P〉0.05 for both CD158a and NKG2A）. The concentrations of IFN-γ and TNF-α secreted by CD56＋ T cells in the patients with chronic HCV infection were significantly decreasedwith or without K562 stimulation （P〈0. 0001 ）. However, in the presence of K562 cells CD107a expression on CD56＋ T cells were sharply decreased in the patients （ P〈0. 0001 ）. In absence of K562 cells, there was no significant change in CD107a expression on CD56＋ T cells from patients and healthy controls （P〉0.05）. The expressions of CD107a, IFN-γand TNF-α were closely related under the stimulation of K562 （r〉0. 80, P〈0.0001 ）. Conclusion The frequency of CD56＋ T ceils was reduced in patients with chronic HCV infec- tion. Moreover, cytotoxic effects and cytokines production mediated by CD56＋ T cells were also significantly impaired, indicating that the dysfunction of circulating CD56＋ T cells might be associated with the persist- ence of chronic HCV infection. 
 
Key words: 
CD56＋ T cells;  Hepatitis C;  Cytotoxic effect;  IFN-γ;  TNF-α