Results of tuberculin test, interferon gamma release test in diagnosis of tuberculosis and correlation with T cell response to tuberculosis

Tuberculosis is a chronic granulomatous infection caused by mycobacteria. Children acquire the tuberculosis bacilli by the inhalation route from adults who expectorate the bacilli. Early diagnosis and treatment of childhood tuberculosis is important for prevention of disease transmission in the population. Correct diagnosis, estimation of the prognosis and treatment of people with latent infection before active disease develops is important in the battle against tuberculosis. However, diagnosis of tuberculosis is difficult in children. INF-? release assays are promising in this aspect besides the traditional diagnostic techniques. It is known that the immune response of the host determines the disease state that develops after contact with MTB bacilli. Balance between TH1 and TH2 lymphocytes are also important for the immune response in which TH1 lymphocytes play a major role. Therefore, determination of the TH1 and TH2 type responses and levels of the cytokines secreted after contact with the bacilli will guide the diagnosis and treatment approaches in tuberculosis.Total of 58 children were enrolled in our study; 14 in the control group, 44 in the patient group. QFT-GIT which is one of the IFN-? release assays was used to differentiate the LTBI and patient groups. Children who were QFT-GIT negative were regarded as LTBI.The aim of this study was to evaluate the TST and Quantiferon tests in childhood tuberculosis and to determine the TH1 and TH2 cytokine responses in the different clinical outcomes.In our study, TGF- ß levels were lower in patient and LTBI groups when compared to the control group (p=0.007 and p=0.014 respectively). IL-17 levels were significantly lower in the LTBI group when compared to the control group (p=0.014). This might indicate that IL-17 is important in transmission from LTBI to active TB.Understanding the immunopathogenesis has a key role in diagnosis and treatment of tuberculosis in children. When data from previous studies and from our study are considered, more number of studies in which high number of cases are enrolled are required.Key words: Childhood tuberculosis, INF-? release assays, immune response, cytokines