Bacterial Lysate Increases the Percentage of Natural Killer T Cells in Peripheral Blood and Alleviates Asthma in Children

<b><i>Aims:</i></b> To assess the efficacy of conventional treatment combined with bacterial lysate [OM-85 Broncho-Vaxom (BV)] in the prevention of asthma in children as well as its influence on the number of natural killer T (NKT) cells and their cytokine production. <b><i>Materials and Methods:</i></b> Sixty children diagnosed with asthma were divided into either a BV-treated group (with oral OM-85 BV) or a conventional inhaled corticosteroid (ICS) group. The numbers of NKT cells and CD4+ NKT cells were measured in the peripheral blood by flow cytometry. The levels of IFN-&#947;, IL-4, and IL-10 after the blood cells had been cultured with an NKT cell agonist were detected by ELISA. <b><i>Results:</i></b> After therapy, asthma attacks were significantly decreased compared with before therapy in both groups. However, after therapy, respiratory tract infections were reduced compared with before therapy in the BV-treated group only. Additionally, the frequency of asthma attacks and use of antibiotics in the BV-treated group were lower than in the ICS group. With BV treatment, the numbers of peripheral blood NKT cells and CD4+ NKT cells were higher after therapy than before therapy. After therapy, the ratio of IFN-&#947;/IL-4 and IL-10 levels were increased in the BV-treated group, whereas IL-4 was reduced in the BV-treated group compared with the ICS group. <b><i>Conclusion:</i></b> BV combined with conventional asthma treatment can prevent recurrent respiratory tract infections and suppress the severity of asthma attacks, possibly by altering the rates and cytokines of NKT cells.