Profile of proinflammatory cytokines in children with Mycoplasma pneumoniae pneumonia


 Background: To explore the profile and clinical significance of proinflammatory cytokines in serum and bronchoalveolar lavage fluid (BALF) of children with Mycoplasma pneumoniae pneumonia(MPP) and to elucidate the etiology and pathogenesis of severe MPP (SMPP). Methods: A cohort of 108 children with MPP was divided into SMPP (n=56) and non-severe MPP (NSMPP) (n=52). A total of 40 cases of hospitalized children, who underwent elective surgery, were selected as control group. The levels of proinflammatory cytokines in the serum and BALF were measured by ELISA(Enzyme-linked immunosorbent assay). Results: Compared to the control group, the MPP children showed that the levels of peripheral blood (PB) TNF-a, IFN-g, GM-CSF, IL-17, IL-18, IL-36a, sB7-H1, and sB7-H3 were much higher at the acute phase (P<0.05). Also, they were significantly higher in the SMPP group than that in the NSMPP group (P<0.05). Furthermore, in the SMPP group, the levels of TNF-a, IFN-g, GM-CSF, IL-1b, IL-2, IL-8, IL-36, MPO, MMP-9, NE, sB7-H3 in BALF were significantly higher at acute phase as compared to the control group (P<0.05). sB7-H3 was positively correlated with major proinflammatory cytokines in both PB and BALF specimens. The level of sB7-H3 in PB was >8000 pg/mL was an independent risk factor for SMPP. Conclusions: Excessive inflammation plays a critical role in the occurrence and development of MPP, especially SMPP, and sB7-H3 is an independent risk factor of SMPP.


Introduction
Respiratory infections are common diseases in childhood, among which community- A cohort of 108 children, aged 50.1 ± 32.8 months, was enrolled in the present study. Of these 108, 56 children exhibited SMPP (51.9%), while 52 showed NSMPP (48.1%). The age of the SMPP group was significantly older than that of the NSMPP group (P<0.05).Compared to the NSMPP group,the duration of fever and the median length of the hospital stay was significantly longer in the SMPP group (P<0.05).
In terms of the laboratory examinations, the median levels of the serum C-reactive protein (CRP), the median absolute count, and the percentage of neutrophils in the SMPP group were significantly higher than those in the NSMPP group (P<0.05). Regarding the immune function indicators, the median levels of peripheral blood(PB) IgG and IgA in the SMPP group were significantly higher(P<0.05), especially the IgGs, while no significant difference was observed in the levels of cellular immunity indicators (P>0.05).In terms of bronchoalveolar lavage fluid (BALF) cytology, the proportion of neutrophils and lymphocytes in the SMPP group was significantly higher than that of the NSMPP group, while the proportion of phagocytic cells was lower (P<0.05).
Moreover,all patients in the SMPP group used glucocorticoids (prednisone, methylprednisolone), while the usage rate in the NSMPP group was only 80% (P<0.05).
The comparison of the remaining clinical indicators is shown in Table1. Note: Data in the table are presented as mean ± standard deviation or quartile.
The levels of PB TNF-α, IFN-γ, GM-CSF, IL-17, IL-18, IL-36α, sB7-H1, and sB7-H3 at convalescent phase were significantly lower than those at the acute phase (P<0.05), while that TGF-β was higher (P<0.05). Besides, the levels of PB TNF-α, IFN-γ, GM-CSF, IL-36α, sB7-H1, and sB7-H3 at convalescent phase did not decline to normal, albeit were higher than those in the healthy control group (P<0.05) (Fig. 1).     The interactions between proinflammatory factors were subjected to multivariate regression analysis to identify the factor that was closely related to the length of hospital stay. Although MMP-9 (Table 2) was the identified factor, the most relevant to the CT value was MPO (Table 3). Correlations between B7-H3 and other proinflammatory cytokines The expression of sB7-H3 was significantly increased in both PB and BALF specimens in this study. Further analysis showed that PB sB7-H3 was positively correlated with IFN-γ, GM-CSF, and IL-4 (P<0.05) (Fig. 6). In BALF, sB7-H3 was positively correlated with GM-SCF, MPO, NE, IL-1β, IL-2, and IL-36 (P<0.05) (Fig. 7).  Table 4, the duration of fever (>10 days) and PB sB7-H3 (>8000 pg/mL) were independent risk factors for the occurrence of SMPP. . However, the present study found that the levels of LDH in the SMPP and NSMPP groups did not vary significantly, which might be related to the incomplete similarity of the study subjects. The participants of this study included children with SMPP, as well as those with refractory MPP. In addition, sample capacity is also one of the reasons for the differences. Recently, some studies reported that in children with MPP, the levels of PB IFN-γ, IL-4, and IL-10 were significantly higher than those in healthy children; however, the level of IL-2 was significantly decreased [26]. The changes in the level of IFN-γ was consistent that the results of the present study. However, any significant change was not found in the levels of IL-4 and IL-2, which might be related to the sample capacity, age, and severity of illness in the enrolled subjects. The more severe the disease, the more pronounced Th1type response. In contrast, those with the mild and persistent disease, the Th2-type response was more pronounced.  Comparison of PB proinflammatory cytokine levels in the NSMPP and SMPP groups at the acute phase Correlation between sB7-H3 and GM-CSF, MPO, NE, IL-1β, IL-2, and IL-36 in BALF