Tuberculosis and factors determining severity.

The balance between nature and nurture and the development of disease is complex. Nutrition clearly has a major role in the health of an individual.
However infections are another major factor.
An article in Nature
Kaufmann 2008, Deadly combination Nature vol 453 p 295-6
describes that not only does the genetic make up of the individual dictate vulnerability to tuberculous infection but also the genetic structure of the tubercle strain.
Normally when a tubercle bacteria reaches the lungs as a droplet, the immune mechanism of the lungs removes the infection. If however the tubercle can bypass this response then an infection results. Detection of the pathogen is through recognition receptor TLR-2 on the surface of the macrophages followed by a signalling cascade mediated by the TLR-2 adaptor protein. T cell white cells are involved.
If the tubercle can bypass this process then infection ensues.
Polymorphism is a feature of tuberculosis and hence the threat from infection persists
I have always felt that the ravages of tuberculosis in 19th century Europe have altered the genetic structure of the surviving families. The survivors for whatever reason were different from the population entering the 19th century.
Many factors would affect survival. Overcrowding, awful working conditions, nutrition and sunlight to name but a few.

Martin Eastwood
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