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Tuberculosis, ethnic differences, and vitamin D – July 2013

Ethnic Differences Affect Immune Response To Tuberculosis Infection

Comment by VitaminDWiki Does not appear to mention the lower vitamin D levels in those with dark skins

AsianScientist (Jul. 5, 2013) – Health & Medicine
The immune response to the bacterium that causes tuberculosis (TB) varies between patients of different ethnic origin, according to a new UK study.

The study, published in the journal PLOS Pathogens and led by researchers at Queen Mary, University of London, analyzed the immune response of 128 newly-diagnosed TB patients in London who were divided by ethnicity into those of African (45), European (27), Asian (55) or mixed European/Asian (1) ancestry.

Note by VitaminDWiki: This study had almost 4X more TB patients with dark skins than light skins

TB is a bacterial infection caused by Mycobacterium tuberculosis. It commonly affects the lungs, and while TB can affect any part of the body, only TB of the lungs or throat is infectious.

While TB grew rare in the UK due to BCG vaccination, improvements in living standards and the introduction of effective antibiotic treatment, it has been on the increase since the late 1980s. TB also remains a major global health problem, responsible for nearly nine million new cases and 1.4 million deaths in 2011.

By analyzing the levels of various inflammatory markers in blood samples taken before treatment, the scientists showed that immune responses of Asians and Europeans were similar to each other, but different from those of Africans. This difference was caused by ethnic variation in the patients’ genetic make-up.

Experiments with white blood cells cultured in the lab showed that different strains of the TB bacterium elicit different amounts of inflammation. Project leader Dr Adrian Martineau explained that 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.

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,” he said.

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 biomarkers, which correlated with either fast or slow clearance of the TB bacteria, were identified and found to differ between Africans and Europeans/Asians.

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.

“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,” said Dr Martineau.

Dr Anna Coussens, who measured immune responses in patient samples at the MRC National Institute for Medical Research, London (NIMR), said that the findings have important implications in the development of new diagnostic tests and biomarkers, which will need to be validated in different ethnic populations before use.

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2730 Ethnic TB.pdf PDF 2013 admin 05 Jul, 2013 21:09 2.05 Mb 812
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