Immune Response in Tuberculosis

INTRODUCTION: Tuberculosis is a global emergency. One third of the world's population is infected, and although only about 5–10% develops active disease during the first few years following exposure 1, this still results in a massive case load, with eight million new cases each year, and three million deaths. Moreover, the percentage that progresses to disease is increasing. Tuberculosis is one of the first secondary infections to be activated in human immunodeficiency virus (HIV)-positive individuals. Moreover the stresses of poverty, malnutrition and war, increase the rate of reactivation for reasons discussed later. Even in developed countries such as the United Kingdom, the disease distribution in large cities parallels the distribution of poverty. Meanwhile the breakdown of healthcare systems is leading to incomplete case and contact tracing, incomplete treatment, and increases in drug resistance. In some parts of the world, many of the available drugs are fake or out of date. In many areas, existing treatment is probably doing more harm than good, as incomplete treatment regimens select for drug resistance. OBJECTIVES: 1. To study immune responses in Tuberculosis with respect to Th1 and Th2 immunity, so that in future immunotherapy of Tuberculosis can be targeted. 2. To compare the systemic and local immune responses in tuberculous pleural effusion patients. MATERIALS AND METHODS: Study subjects: Blood and PF were collected from 51 patients from our wards before the start of the treatment. The mean age of the study subjects was 38 years (range 18- 65 years). These patients were seronegative for human immunodeficiency virus (HIV). The blood and the PF samples collected for diagnostic and therapeutic purposes were utilised for the study. A written and informed consent was obtained from each patient. The collection of the samples and the study followed the ethical guidelines of Government General Hospital, Chennai. Pleural effusions were defined as exudative using Light’s criteria. Light’s criteria: The pleural fluid is an exudate if one or more of the following criteria are met: • Pleural fluid protein divided by serum protein >0.5. • Pleural fluid LDH divided by serum LDH >0.6. • Pleural fluid LDH more than two-thirds the upper limits of normal serum LDH. Of the total, 51 patients were diagnosed to have tuberculosis based on the ; 1. Smear for AFB, 2. Culture of the fluid (BACTEC), 3. Polymerase chain reaction (PCR) positivity (IS6110 specific) of the sputum or the PF together with the clinical picture. These 31 patients showed positivity in at least any two of the above criteria and hence were categorised as TB group. Statistical Analysis: Data are presented as the mean and S.E.M. in both text and in figures. For normally distributed data, comparisons between groups were done with the paired or unpaired Student’s t-test, as appropriate. For data that were not normally distributed, the Wilcoxon rank sum test was used. P < 0.05 was considered to be statistically significant. CONCLUSION: 1. In this study, we confirmed that cytokine status and T-cell reactivity within the tuberculous pleural effusions were polarized strongly toward a Th1 response. 2. Compartmentalisation of lymphocytes in pleural effusion occurs in the lymphocyte population in cases of tuberculous pleural effusion