Immunology and pathogenesis of childhood TB

Jones, Christine, Whittaker, Elizabeth, Bamford, Alasdair and Kampmann, Beate (2011) Immunology and pathogenesis of childhood TB. Paediatric Respiratory Reviews, 12 (1), 3-8. (doi:10.1016/j.prrv.2010.09.006).

Abstract

Tuberculosis (TB) in children most commonly results from exposure to a household contact with active TB, and represents ongoing transmission of Mycobacterium Tuberculosis (Mtb) in the community.1 Infants and young children have an increased risk of infection following exposure and progress more readily from infection to active TB disease; in the absence of intervention, infants have a 50-60% risk of disease in the first year following infection.2, 3 It could therefore be argued that the determining factor for the higher susceptibility to disease in children is prolonged, intimate contact between the child and the index case, which might lead to a larger inoculum of Mtb. However, there is little evidence to support this assumption, since the mycobacterial load in children is notoriously low, which lies at the root of the problem of bacteriological confirmation of primary TB. Young children more commonly present with disseminated disease and have an increased risk of death.2 Even low bacillary loads in children can lead to acute and severe illness, be it respiratory or disseminated, especially in children younger than 2 years of age. The generally accepted assumption is therefore that qualitative and quantitative differences in the immune responses to Mtb infection between adults and children determine outcome. In the following review, we describe the multiple factors involved in containment of mycobacteria and review potential differences between responses in adults versus children. We have chosen to base this article primarily on studies conducted in the human host and - where available - in children. It is however obvious that crucial data on the impact of age on many of the cited factors are missing from the published literature, and we indicate where further studies would be warranted in this context.

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Contributors

Author: Christine Jones

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