Abnormalities of quantities and functions of CD56bright natural killer cells in non-severe aplastic Anemia

The mechanism of non-severe aplastic anemia (NSAA) is not clear. It may be different from severe aplastic anemia (SAA). CD56bright NK cells (regulatory NK cells) is a subgroup of NK cells that produce immunoregulatory cytokines and express high-affinity IL-2 receptor. To investigate CD56bright NK cells quantities and function in patients with NSAA and to explore how CD56bright NK cells participate in the progress of this disease.

In this study, we analyzed the quantitative and functional changes of CD56bright NK cells in peripheral blood of patients with NSAA by using Flow Cytometry (FCM) before and after immunosuppressive therapy (IST). The expressions of activating receptor (NKG2D, NKp46, NKp44), inhibitory receptor (NKG2A, CD158a, CD158b) and perforin and granzyme B were detected by FCM. IL-2 and IL-18 levels in serum were detected by ELISA. The correlation between these parameters and clinical indicators of patients were evaluated.

We found that the percentage of CD56bright NK cells in newly diagnosed NSAA patients was higher than that in normal controls (p = .011, p < .05). The median expression of NKG2D in patients with NSAA was higher compared to that in normal controls (p = .021, p < .05), and the expression of CD158a was lower (p = .047, p < .05). The concentrations of IL-2 and IL-18 in the serum of patients with NSAA were higher than those in normal group.

These findings suggest that increased and activated CD56bright NK cells might play a protective role in the pathogenesis of NSAA.