Characterization of Intermediate TCR Cells in the Liver of Mice with Respect to Their Unique IL-2R Expression

We previously demonstrated that T cells with intermediate TCR intensity (i.e., intermediate TCR cells) which possibly generate extrathymically are preferentially present in the liver of mice. This population was further characterized with respect to the expression of IL-2 receptor (IL-2R) and others. Two-color staining for CD3 (or TCR αβ) and IL-2R α (and β) demonstrated that intermediate TCR cells as well as NK cells constitutively expressed IL-2R β but not IL-2R α. A small number of intermediate TCR cells was also identified in other immune organs by using this staining method. In vivo and in vitro stimulation experiments revealed that regular, bright TCR cells, which originally lacked the expression of both IL-2R α and β, acquired the highest expression of IL-2R α and β, while intermediate TCR cells did not. These results suggested, in conjunction with their other properties demonstrated here, that intermediate TCR cells might be more primitive T cells than regular T cells of thymic origin.