RESUMEN
Objective:To discuss the changes and clinical significance of CD4 -CD8 -double negative T lymphocytes (DNT), T lymphocyte subsets, natural killer (NK) cells and CD 19+ B lymphocytes in peripheral blood of children with confirmed Mycoplasma pneumoniae pneumonia(MPP). Methods:A retrospective analysis was conducted on children with pneumonia admitted to the Children′s Hospital of Shanghai Jiaotong University from January 2019 to February 2020.The patients were stratified into 3 age groups: 0-3 years old, 4-7 years old and ≥8 years old, and they received detection of peripheral blood T lymphocyte subsets in acute stage.As observation group, 185 MPP children were further divided into MPP common group (117 cases) and MPP severe group (68 cases) based on their state of pneumonia.In addition, 69 cases with non-MPP were selected as control group.The absolute counts of DNT, T lymphocyte subsets, NK cells and CD 19+ B lymphocytes in peripheral blood were tested by flow cytometry.DNT levels in diffe-rent age groups were analyzed. Results:(1) The number of CD3 + [1.527(1.059, 2.348)×10 9/L], CD4 + [0.771(0.559, 1.206)×10 9/L], CD8 + [0.528(0.343, 0.773)×10 9/L], CD4 + /CD8 + [1.570(1.130, 1.945)], CD 19+ [0.455(0.285, 0.771)×10 9/L] and DNT[0.168(0.095, 0.294)×10 9/L] lymphocytes in peripheral blood in the observation group were lower than those in the control group[2.116(1.506, 3.728)×10 9/L, 1.170(0.685, 2.114)×10 9/L, 0.696(0.414, 1.226)×10 9/L, 1.780(1.230, 2.210), 0.694(0.483, 1.343)×10 9/L, 0.235(0.134, 0.391)×10 9/L], and the differences were statistically significant (all P<0.05). (2) In addition, the number of CD3 + [1.704(1.215, 2.566)×10 9/L], CD4 + [0.855(0.628, 1.267)×10 9/L], CD8 + [0.582(0.378, 0.843)×10 9/L], NK[0.269(0.176, 0.417)×10 9/L], CD 19+ [0.461(0.317, 0.808)×10 9/L] and DNT[0.180(0.117, 0.306)×10 9/L]lymphocytes in peripheral blood in MPP common group were significantly higher than those in MPP severe group [1.369(0.831, 1.760)×10 9/L, 0.676(0.433, 0.924)×10 9/L, 0.495(0.292, 0.699)×10 9/L, 0.196(0.112, 0.380)×10 9/L, 0.391(0.181, 0.730)×10 9/L, 0.143(0.071, 0.265)×10 9/L], and the differences were statistically significant (all P<0.05). (3) Moreover, in acute phase, the number of DNT in observation group had no significant differences with that in control group of the same age ( P>0.05). In the observation group, the number of DNT[0.230(0.125, 0.364)×10 9/L] in 0-3 years old group was higher than that in 4-7 years old group[0.143(0.085, 0.233)×10 9/L] and ≥ 8 years old group[0.144(0.078, 0.271)×10 9/L]. In 0-3 years old group, the more serious the disease, the lower the indicators, and the differences were statistically significant (all P<0.05). Conclusions:In acute phase, the changes of lymphocyte subsets in peripheral blood of MPP children are remarkable, and the absolute count of DNT lymphocytes in peripheral blood decreased.The decreasing level of DNT has negative association with the severity of pneumonia.The absolute count of DNT was higher in young children.So monitoring peripheral blood DNT may be of some value to the assessment of immune function or pneumonia state in children with MPP.