Scientists have discovered that the strategy of "immune evasion" common to many viruses, bacteria and parasites, is uncommon to M. tuberculosis where the antigens remain strikingly unchanged and homogeneous. The study suggests that M. tuberculosis antigens do not mutate because they hope to be recognized by the body's immune system -- perhaps because the host immune mechanism that leads to the typical lung destruction and cough can contribute to the spread of the disease. This finding has the potential to change the direction of vaccine research and could result in a new focus on different targets of immune response to the bacteria.