[Characteristics of peripheral blood lymphocyte subsets in children with mycoplasma pneumoniae pneumonia under different infection states].

The research investigated the characteristics of lymphocyte subsets in peripheral blood of children with mycoplasma pneumoniae pneumonia in different infection states. The retrospective cross-sectional study selected 194 children with pneumonia from October 2023 to January 2024 in Zhongnan Hospital of Wuhan University as the study objects, patients aged 7 months to 13 years old, including 91 female children and 103 male children. According to the types of pathogens, the children with pneumonia were divided into single MP infection group (80 cases), non-MP infection group (29 cases) and mixed pathogen infection group (85 cases). According to the mutation of MP23S rRNA gene, the MPP children were divided into drug-resistance group (112 cases) and non-drug-resistance group (53 cases). According to the results of bronchoscopy and imaging, the MPP children were divided into severe group (35 cases) and mild group (130 cases). Pathogen infection, the percentage and absolute count of lymphocyte subsets in peripheral blood, hypersensitive CRP, interferon-γ, tumor necrosis factor-α, interleukin-10, interleukin-4, interleukin-6 and interleukin-2 in each group were analyzed retrospectively. The levels of the test items in each group were compared. The value of peripheral blood lymphocyte subsets in the diagnosis of MPP in children was evaluated by ROC curve. The results showed that the co-infection rate of MPP children was 51.51% (85/165). Streptococcus pneumoniae was the most common co-infection (39/85, 45.88%), followed by Haemophilus influenzae (26/85, 30.89%). The mutation rate of MP resistance gene was 67.88% (112/165) in MPP children tested for tNGS in bronchoalveolar lavage fluid. The absolute counts (cells/μl) of CD3⁺, CD3⁺CD4⁺, CD3⁺CD8⁺, CD3^-CD19⁺, CD3^-CD16⁺CD56⁺and CD3⁺CD16⁺CD56⁺ in the simple MP group (1 164, 612, 415, 242, 168, 50) and the mixed pathogen group (1 285, 694, 457, 313, 176, 52) were significantly lower than those in the non-MP group (2 092, 1 037, 660, 541, 295, 86) (<i>P<</i>0.05). There was no significant difference between drug-resistant group and non-drug-resistant group (<i>P></i>0.05). The CD3⁺CD4⁺% (34.91) and the absolute counts of CD3^-CD16⁺CD56⁺ (148 cells/μl) in severe group was significantly lower than that in mild group (37.91, 187 cells/μl), and CD3^-CD19⁺% (19.48) was significantly higher than that in mild group (16.33) (<i>P<</i>0.05). The median values (cells/μl) of CD3⁺ (1 093, 925), CD3⁺CD4⁺ (576, 543), CD3⁺CD8⁺ (401, 356), CD3^-CD19⁺ (238, 234) and CD3^-CD16⁺CD56⁺ (181, 153) in MPP children aged 4 to 8 years and 9 to 12 years were lower than the reference range in corresponding age. ROC curve analysis showed that the AUC of peripheral blood lymphocyte subsets for MPP diagnosis was 0.813, and the sensitivity was 79.3%, the specificity was 75%. In conclusion, the co-infection rate of MPP children was higher than single MP infection. The characteristics of peripheral blood lymphocyte subsets in children with pneumonia were that the absolute count test value of MPP children was significantly lower than that of non-MP infection, and there are differences between MPP children clinical types.