Cytokine production and responsiveness of fetal T-cell receptor V gamma 3 thymocytes

Langerhans cells that have matured in vivo in the absence of T cells are fully capable of inducing a helper CD4 as well as a cytotoxic CD8 response

Langerhans cells (LCs) are immature dendritic cells (DCs) present in the skin epithelium. Upon Ag exposure, they migrate to the draining lymph nodes where they mature into potent stimulators of naive T cells. The aim of this study was to investigate the influence of T cells on LC migration and maturation. Therefore, the in vivo migration and maturation of LCs after sensitization with the hapten FITC was compared between C57BL/6 or BALB/c mice used as positive controls, and recombination activating gene (RAG) 1 knockout (-/-) mice or SCID mice used as T cell-deficient mice. Phenotypically, there was no difference between migrated LCs from RAG1-/- or SCID mice vs normal C57BL/6 or BALB/c mice: both populations of FITC+ cells had a dendritic morphology and a mature phenotype as they expressed high levels of MHC class II molecules and costimulatory molecules CD80, CD86, and CD54. Sorted migrated LCs of RAG1-/- or SCID mice were efficient stimulators of allogeneic T cells and Ag-specific CD4+ T cells. The same results were found if migrated LCs were fixed instead of irradiated, excluding the possibility that LCs derived from RAG1-/- or SCID mice would mature in the presence of T cells during the stimulation tests. Importantly, fixed migrated LCs of RAG1-/- mice were also efficient stimulators of cytotoxic CD8+ T cells. These data suggest that T cells are not required for full maturation of LCs.

Immunobiology of mouse dendritic epidermal T cells: a decade later, some answers, but still more questions

Over the past decade, overwhelming evidence has accumulated in many species, most notably in mice, that epithelial sites such as skin, intestine, and reproductive tract are populated with relatively discrete subsets of gamma delta cells. Such studies have identified several distinguishing and, in some cases, unique features of the dendritic epidermal T cells (DETC) populating the skin of all normal mice: homogeneous V5-J1-C gamma 1/V1-D2-J2-C delta T-cell receptors devoid of junctional diversity, apparent tissue restriction in adult mice to the skin, an important role for active hair growth in their localization and/or proliferation in the skin, and a capacity to recognize an antigen expressed on stressed epidermal cells. These properties have led to the hypothesis that DETC play distinctive roles in cutaneous immune surveillance and/or immunoregulation via recognition of a common self-antigen expressed by adjacent cells under various potentially harmful circumstances. Despite substantive advances in our knowledge about gamma delta cells in general (e.g., recent evidence that their manner of antigen recognition may be fundamentally different from that used by conventional alpha beta T cells) and about epithelial-specific subsets such as murine DETC in particular, it is clear that, compared with our understanding of alpha beta cells, major gaps still exist in our understanding of these cells. Persisting questions about DETC include: precise identification of the ligands for their homogenous T-cell receptors, the cellular and molecular requirements for their activation, their full range of functional activities, the reason(s) for the absence in normal human skin of a precise morphologic and phenotypic homologue, and, perhaps most important, their biologically relevant role(s) in cutaneous physiology, immunity, and/or pathology.