Objective To analyze the percentage and functional changes of natural killer T (NKT) cells in peripheral blood and bone marrow of severe aplastic anemia (SAA) children before immunosuppressive therapy (IST) comparing to that of healthy children.Methods Ten children with severe aplastic anemia were included in the study and ten healthy children at the same age were selected as the control group. By lfow cytometry, the percentage of CD3+CD1d tetramer+ NKT cell in peripheral blood and bone marrow were detected from March 2014 to December 2014 in our hospital. Immune magnetic bead separation was used to isolate and purify iNKT cells .The puriifed iNKT cells were cultured in the OCH(50 ng/ml,100 ng/ml or 200 ng/ml)+rhIL-2+rhG-CSF culture systems. The ampliifcation of iNKT cells after cultured in different systems were calculated. Elispot method was used to analyze the spotting form cells (SFCs) of IFN-γ or IL-4 expressed by activated iNKT cells.Results The percentage of CD3+CD1d tetramer+ NKT cells in peripheral blood of SAA group(0.72±0.03)% was signiifcantly lower than that of the control group(0.92±0.02)%(P=0.000). The percentage of CD3+CD1d tetramer+ NKT cells in bone marrow of SAA group(0.82±0.02)% was signiifcantly lower than that of the control group(1.05±0.05)%(P=0.000).In vitro iNKT cell ampliif-cation ability of bone marrow in SAA group was signiifcantly lower than the control group, and in medium concentration(50±6) and high concentration OCH group(52±6), the ampliifcation ability was higher than that in low concentration OCH group(30±5) (P<0.05). The secretion of IFN-γ in the iNKT cells of SAA bone marrow was signiifcantly lower in medium concentration(33±3) and high concentration(35±3)OCH group than that of the low concentration(50±3)OCH group(P<0.01). The secretion of IL-4 in the iNKT cells of SAA bone marrow was signiifcantly higher in medium concentration(50±3)and high concentration(75±3) OCH group than that of the low concentration(33±3) OCH group(P<0.01).Conclusions The quantity and function of NKT cells from children with SAA are lower than that of the healthy children.In vitro, they had better ampliifcation ability and could improve IL-4/IFN-γ imbalance in medium concentration and high concentration OCH group than in low concentration OCH group.

Antibodies, Neutralizing/immunology* ; Antibodies, Viral/immunology* ; COVID-19/virology* ; COVID-19 Vaccines/immunology* ; Humans ; SARS-CoV-2/pathogenicity* ; Spike Glycoprotein, Coronavirus/immunology* ; Vaccines, Inactivated/immunology*