Relationship Between Vitamin A?D Deficiency And Bronchiolitis In Infants And Younger Children

Bronchiolitis(also known as acute infectious bronchiolitis)is a common lower respiratory tract infection in infants and young children.It is more common in infants under 2 years.Cough and wheeze are the main clinical features.Epidemiological studies have shown that children with bronchiolitis can experience repeated episodes of wheezing and are prone to develop asthma.The pathogenesis of bronchiolitis has not yet been fully elucidated,and it is currently believed that imbalance of Th1/Th2 and Treg/Th17 accounts for an important role.In addition,innate immunity,humoral immunity and lung development also affect its onset and condition.The presence of vitamin A supplementation is beneficial in the prevention and treatment of bronchiolitis.Vitamin A and its metabolite retinoic acid can promote the function of Treg cells and inhibit the function of Th17 cells.Vitamin A can promote the repair of respiratory epithelium,promote B lymphocyte synthesis of Ig G,Ig M,Ig A,can also regulate dendritic cells(Dendritic cells,DCs)and regulate respiratory immune response.In the absence of vitamin A,humoral immunity and cellular immunity are impaired,and respiratory epithelial cells are keratinized and mucosal secretion is reduced,thereby weakening the anti-infective barrier.When the level of vitamin A decreases,the level of dendritic cells in the local mucosa increases,which promotes inflammatory reactions and causes tissue damage.Vitamin A supplementation also has the disadvantage of reducing the incidence and condition of bronchiolitis.Vitamin A deficiency can upregulate the Th1-mediated immune response.Vitamin A supplementation can upregulate Th2 cell-mediated immune response and down-regulate Th1 immune response.Therefore,which area dominates determines whether vitamin A supplementation is beneficial to the recovery of bronchiolitis.Several studies have found that infants with low cord blood vitamin D levels have an increased risk of having wheezing disorders.This shows that there is a correlation between serum vitamin D levels and the incidence of bronchiolitis.Vitamin D can attenuate the Th2 response by inhibiting IL-4 and IL-13,induce the production of Treg cells that specifically secrete IL-10,and reduce the production of pro-inflammatory factor IL-17.Studies have shown that vitamin D deficiency can cause B lymphocyte differentiation and maturation disorders,resulting in low immunoglobulinemia,manifested as Ig G,Ig A decreased.At the same time,vitamin D can stimulate lung epithelial cells to express antibacterial peptides and beta-defensins.These endogenous antibiotics have a broad spectrum of antimicrobial activity and can directly kill microorganisms that invade the body,inactivating the virus.Animal experiments show that vitamin D can also affect the number of alveoli,lung volume,alveolar septum thickness,airway resistance,and immune cell aggregation,thereby affecting lung development.Therefore,vitamin D may be beneficial to the recovery of bronchiolitis by regulating cellular immunity,humoral immunity,innate immunity,and lung development.Objectives: By measuring serum vitamin A?D levels in children with bronchiolitis and healthy infants,the relationship between vitamin A?D deficiency and pediatric bronchiolitis was explored.Methods: From September 2015 to March 2017,we collected hospitalized treatment in the Department of Pediatric Respiratory Medicine.Children meeting the diagnostic criteria for bronchiolitis were designated as the bronchiolitis group,and the control group was set as the healthy children in the same age group at the same time in the outpatient examination.Follow relevant inclusion and exclusion criteria.The vitamin A and vitamin D2 groups were included in the bronchiolitis group and the control group in 60 cases each.The blood samples of the children were collected and the levels of serum vitamins A and D were measured by chromatographic analysis and their basic information such as age was collected.All data were analyzed using SPSS21 software.Results:(1)Compared with the control group,the levels of serum vitamin A in the bronchiolitis group were lower than those in healthy children,but P>0.05,no statistical difference.(2)Compared with the control group,the serum vitamin D level in the bronchiolitis group was lower than that in healthy children,and there was a statistical difference between P<0.05.Conclusion:(1)Serum vitamin A levels in children with bronchiolitis were not significantly different from those in healthy children.(2)The level of serum vitamin D in children with bronchiolitis was significantly lower than that in healthy children.Whether vitamin D supplementation can reduce the incidence of bronchiolitis remains to be further studied.