CD1-autoreactive T cells of two types have been demonstrated among T cells expressing the T-cell receptor (TCR) alphabeta at intermediate levels (TCRint cells). One type constitutes a major fraction of the natural killer (NK)1.1+ TCRint population in C57BL/6 (B6) mice and carries a restricted TCR composed of an alpha-chain with an invariant Valpha14-J281 rearrangement, and a beta-chain using Vbeta8. 2, 7 or 2. The second type utilises a variety of TCR and was derived from CD4+ cells in mice lacking MHC class II. To increase our understanding of the two different CD1-reactive subsets, we have investigated and compared the populations of origin: NK1.1+ and NK1. 1- TCRint subsets from MHC class II-deficient mice and CD4+NK1.1+ T cells from B6 mice. The three TCRint populations shared a phenotype indicating previous activation, and contained low frequencies of cells expressing NK receptors of the Ly49 family. In contrast to control CD4+ cells, the three TCRint subsets produced high amounts of interleukin (IL)-4 and interferon (IFN)-gamma after activation. Importantly, no IL-10 could be detected in either TCRint population, implying a distinct function for these cells, different from those of conventional CD8+ and CD4+ cells, including the typical T-helper 2 (Th2) cell. Analysis of TCR expression indicated that the proportion of cells using the semi-invariant Valpha14/Vbeta8.2-type TCR was lower in NK1.1+ cells from MHC class II-negative mice than in CD4+NK1.1+ B6 cells. Further, usage of the Valpha14-J281 rearrangement was also demonstrated among NK1.1- TCRint cells.

Fritsch M, Ivars F. gd T-Cell Precursor-Derived CD4 -CD8 -ab T Cells Retain gd Cell Function. Scand J Immunol 1998;48:8-14 We have previously shown that some of the DNab þ T cells arising in TcRa-chain transgenic mice are of gd T cell origin, based on phenotypic data and on their status of TcR gene rearrangements. In the present report we investigated the impact of ab TcR expression on the functional programme of the mature gd precursorderived DNab þ T cells. Our results demonstrate that both their proliferative capacity and their cytokine production profile are similar to that of gd T cells. Furthermore, both transgenic DNab þ T cells and DNgd þ T cells up-regulate CD8a expression after activation, but, in contrast to CD4 þ ab T cells, are unable to induce proliferation of naive B cells. Thus, our results suggest that the effector functions of mature T cells are determined independently of the TcR isotype, probably at an early stage of differentiation, and thereby have important implications for current models of T-cell lineage commitment.