Tuberculosis immunology in children: diagnostic and therapeutic challenges and opportunities

Tuberculosis (TB) is one of the most important causes of infectious morbidity and mortality worldwide. Young children are more likely to develop severe disease from the causative agent Mycobacterium tuberculosis. These clinical observations likely reflect fundamental differences in the immune systems of young children and adults. Essential to effective TB immunity are functioning macrophages, dendritic cells, strong Th1-type T-cell immunity and a relative absence of Th2-type T-cell immunity. Critical differences between adults and children relevant to TB immunity include deficiencies in macrophage and dendritic cell function, deficiencies in the development of Th1-type T-cells in response to pathogens, and the propensity for infants and young children to develop Th2-type CD4(+) T-cells in response to immunogens. In this article, knowledge about the requisite components of protective immunity, differences between the immune systems of children and adults relevant to pediatric tuberculosis, M. tuberculosis-specific T-cell immunity in children, and potential application to immunodiagnostics and vaccine development will be reviewed.