Objective To investigate the effects of high mobility group protein 1(HMGB1) on monocyte immune function in children with respiratory syncytial virus(RSV) bronchiolitis and henoch-schonlein purpura(HSP).

Methods A total of 30 hospitalized children with RSV bronchiolitis complicated with HSP were selected as the observation group, and 30 healthy full-term infants who underwent physical examination during the same period were selected as the control group. Plasma samples were collected from the two groups after admission, the routine blood cell analysis and C reactive protein(CRP) level detection were performed, and the serum expression levels of HMGB1 in two groups were detected using ELISA. The human bronchial epithelial cell line 16HBE was transfected with recombinant RSV-A2 virus, and the HMGB1 level in cell culture supernatant was detected. RSV-infected cells, human bronchial epithelial cell line 16HBE and monocyte THP1 were co-cultured by hole plates, the total RNA of cells was determined by qRT-PCR, and the expression levels of Toll-like receptor TLR-4 and TLR-7 of monocytes were detected using Western blotting.

Results Compared with the healthy control group, the serum expression level of HMGB1 in RSV bronchiolitis children complicated with HSP was significantly higher(t=5.84, P < 0.05). The number of monocytes, peripheral lymphocytes and serum CRP level were positively correlated with the serum level of HMGB1 in RSV bronchiolitis children complicated with HSP(r=0.606, 0.301, 0.394, P < 0.05). The number of monocytes in peripheral blood was the most significantly correlated with serum level of HMGB1(P < 0.05). The result of qRT-PCR showed that the HMGB1 level in 16HBE cell culture medium after virus transfection significantly increased compared with that in control group(t=5.41, P < 0.05). After co-culture of RSV-transfected 16HBE cells, infection control group and HMGB1 inhibited group with monocyte THP-1, the expression levels of TLR-4 and TLR-7 proteins in monocytes were detected by Western blotting, and the results of which showed that the expression level of TLR-4 in THP-1 cells significantly increased(P < 0.05), while the change of TLR-7 level was not significant(P>0.05).

Conclusions The expression level of HMGB1 is related to the development of RSV bronchiolitis complicated with HSP. HMGB1 plays an important role in monocyte-mediated immune inflammation, which is of great significance to understand the pathogenesis of pediatric RSV bronchiolitis.