Bacillus Calmette-Guerin vaccine scar diameter and asthma

Background: The extent of T-helper cell type 1/type 2 (Th1/Th2) balance during the neonatal period may be the key determinant of how the genetic predisposition to asthma is modulated and may be useful in predicting its subsequent development. The bacillus Calmette-Guerin (BCG), when administered intradermically, induces, even in newborns, a significant increase in the response of cytokines derived from Th1 lymphocytes. Studies have shown that tissue reactions at the site of the BCG vaccination are proportional to the production of interferon gamma (IFN-gamma) in response to the mycobacterial antigens. There was no significant correlation between the size of tuberculin skin test and IFN-gamma production. Methods/Data base: A search of the literature was performed using the Medline database with the words "BCG scar" and "asthma" and only seven scientific studies were found. Of these, only three have discussed the question concerning BCG scar diameter and asthma, all of which were carried out by our group and are presented in a condensed way in this review article. Results/Conclusions: The deficient response to the BCG vaccine scar can be a characteristic of asthma regardless of the presence of atopy. Asthmatic individuals with small BCG scars can exhibit a deficiency in production of IFN-gamma, probably as an intrinsic characteristic that could not be altered by the stimulus with BCG.