Ligand-specific αβ and γδ T cell responses in childhood tuberculosis

The αβ and γδ T cell responses were analyzed in the peripheral blood of children affected by active tuberculosis (TB) and in healthy children who tested positive (PPD+) or negative (PPD-) for purified protein derivative. PPD+ healthy and diseased children responded equally well to PPD in vitro. In contrast, only 18% of PPD+ TB patients responded to peptide p38G derived from the 38-kDa protein of Mycobacterium tuberculosis. Analysis of the whole γδ T cell population and of its Vγ9/Vδ2 subset showed similar frequencies in PPD+ children with TB and in healthy PPD+ and PPD- children. Vγ9/Vδ2 cells from children with TB responded to 5 different phosphoantigens similarly to those from healthy PPD+ children, but healthy PPD- children responded very poorly. Chemotherapy had contrasting effects on the tested lymphocyte population, represented by increase of αβ and decline of Vγ9/Vδ2 T cell responses. T cell responses in childhood TB may be similar to those in adult TB.