Developmentally regulated extinction of Ly-49 receptor expression permits maturation and selection of NK1.1+ T cells

Characterization of subpopulations of T-cell receptor intermediate (TCRint) T cells

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.

Cutting Edge: LFA-1 Is Required for Liver NK1.1+TCRαβ+ Cell Development: Evidence That Liver NK1.1+TCRαβ+ Cells Originate from Multiple Pathways

Using mice deficient for LFA-1, CD44, and ICAM-1, we examined the role of these adhesion molecules in NK1.1+TCRαβ+ (NKT) cell development. Although no defect in NKT cell development was observed in CD44−/− and ICAM-1−/− mice, a dramatic reduction of liver NKT cells was observed in LFA-1−/− mice. Normal numbers of NKT cells were present in other lymphoid organs in LFA-1−/− mice. When LFA-1−/− splenocytes were injected i.v. into wild-type mice, the frequency of NKT cells among donor-derived cells in the recipient liver was normal. In contrast, when LFA-1−/− bone marrow (BM) cells were injected i.v. into irradiated wild-type mice, the frequency of liver NKT cells was significantly lower than that of mice injected with wild-type BM cells. Collectively, these data indicate that LFA-1 is required for the development of liver NKT cells, rather than the migration to and/or subsequent establishment of mature NKT cells in the liver.