Race and tuberculosis: By analysing the levels of various inflammatory markers in blood samples taken before treatment, scientists have showed that immune responses of Asians and Europeans are similar to each other, but different from those of Africans

This difference was caused by ethnic variation in the patients’ genetic make-up and was not related to the strain of TB bacterium that the patients were infected with. Dr Adrian Martineau, Reader in Respiratory Infection and Immunity at the Blizard Institute, part of Queen Mary, said: “The TB bacterium has co-evolved with humans following migration to Europe and Asia some 70,000 years ago, and different strains of the TB bacterium disproportionately infect particular ethnic groups. Experiments with white blood cells cultured in the lab have shown that different strains of the TB bacterium elicit different amounts of inflammation. One might therefore expect that TB patients’ immune responses would differ according to the strain of TB bacterium that they are infected with. However our study has shown, for the first time, that it is actually ethnic differences in the patient’s genetic make-up that cause most of this variation in immune responses – with little effect of the TB strain they are infected with.” By analyzing blood samples taken from 85 of the original cohort after an eight-week period of intensive treatment, the researchers found that ethnic variation in immune responses became even more marked. A number of immunological bio-markers, which correlated with either fast or slow clearance of the TB bacteria, were identified and found to differ between Africans and Europeans/Asians. Dr Anna Coussens, who measured immune responses in patient samples at the NIMR, said: “These findings have important implications, both for the development of new diagnostic tests, which increasingly rely on analyzing the immune response, and also for work to identify candidate bio-markers to measure response to anti-TB treatment. In the future, diagnostic tests and bio-markers will need to be validated in different ethnic populations.” A key factor in determining the ethnic variation identified in the study appears to be the patients’ genetic type of vitamin D binding protein – a molecule which binds vitamin D in the circulation. Dr Martineau said: “There are different genetic types of this protein which vary in frequency between ethnic groups, adding to the growing evidence that vitamin D and the way it is carried in the blood is crucial in determining how a patient’s immune system will respond to TB.”