Abstract: OBJECTIVE To explore the MP-DNA load in bronchoalveolar lavage fluid (BALF) of children with Mycoplasma pneumoniae pneumonia (MPP) and analyze its relationship with immune cells. METHODS A total of 24 children who were diagnosed with MPP in the respiratory department of the First People's Hospital of Chenzhou from Oct 2015 to Apr 2016 were enrolled in the study and assigned as the MPP group, meanwhile, 28 children who had bronchial foreign bodies were chosen as the control group.The levels of related inflammatory indexes were compared between the two groups of children, the serum MP antibody titer was detected by using passive agglutination method, the MP-DNA load in BALF was detected by means of real-time fluorescence quantification PCR, and the percentages of the immune cells were calculated by using microscope. RESULTS The levels of serum C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) of the MPP group were respectively (18.30±14.29)mg/L and (32.18±19.85)mm/h, significantly higher than (10.28±12.20)mg/L and (12.67±6.31)mm/h of the control group(P＜0.05),however, there were no significant differences in other indexes between the two groups.The positive rate of serum MP antibody of the MPP group was 79.2%(19/24), significantly higher than 14.28%(4/28) of the control group(P＜0.05).The percentage of neutrophils in BALF was higher in the MPP group than in the control group, while the percentage of macrophages was significantly lower in the MPP group than in the control group(P＜0.05).The percentage of neutrophils in BALF of the children with MPP was positively correlated with the BALF MP-DNA load (r=0.477,P=0.018), while the percentage of macrophages was negatively correlated with the BALF MP-DNA load (r=-0.457, P=0.024). CONCLUSION The MP-DNA and neutrophils are remarkably increased in BALF of the children with MPP, indicating that the MP may activate the neutrophils and induce the immune cells and humoral immune response.