Human T-cell activation deficiencies.

The increasing understanding of T-cell activation is paralleled by the recognition of a growing range of 'experiments of nature' that cause T-cell activation deficiencies. Analysis of these deficiencies is, in turn, contributing to the understanding of T-cell function in vivo. Here, José Regueiro, Antonio Arnaiz-Villena and colleagues review current knowledge of structural and functional T-cell defects and the implications of these for T-cell biology.