Effectiveness of thymostimulin and study of lymphocyte-dependent antibacterial activity in children with recurrent respiratory infections

Recurrent respiratory infections (RRI) consist of more relapsing acute respiratory infections than the ones expected for the age [> 6 acute respiratory tract infections (RTI) per year if age is > 3 years, and > 8 acute RTI per year if age is < 3 years]. Concerning the pathogenesis of RRI, several investigations report the important role of environmental factors, early socialization and immunological dysfunctions, such as lymphocyte subpopulations alterations, IgG subclass deficiency and phagocytosis and/or opsonization deficit during acute infections. In this framework, we have studied the lymphocyte-dependent antibacterial activity (ABA) among 121 children affected by RRI. Results show a statistically significant alteration of this function in 38 children (31.4%): 19 of them exhibited an absent ABA (group 1), while in the others same function was reduced (group 2). A bovine thymic extract, thymostimulin, was administered to both groups by intramuscular injections (1 mg/kg) for a 3 month cycle. At the end of therapy we observed a statistical significant rise of ABA only in group 1 and among children aged > 3 years. Among the same patients, 33 children (86.8%) improved in terms of reduction of clinical score and better results were seen among children aged > 3 years. These data emphasize the beneficial role of thymostimulin in RRI-affected children, suggesting a transient immaturity of the immune system as one of the possible pathogenetic factor.