T cell receptor expression by dendritic epidermal T cells

T cell development in mice lacking all T cell receptor zeta family members (Zeta, eta, and FcepsilonRIgamma)

The zeta family includes zeta, eta, and FcepsilonRIgamma (Fcgamma). Dimers of the zeta family proteins function as signal transducing subunits of the T cell antigen receptor (TCR), the pre-TCR, and a subset of Fc receptors. In mice lacking zeta/eta chains, T cell development is impaired, yet low numbers of CD4+ and CD8+ T cells develop. This finding suggests either that pre-TCR and TCR complexes lacking a zeta family dimer can promote T cell maturation, or that in the absence of zeta/eta, Fcgamma serves as a subunit in TCR complexes. To elucidate the role of zeta family dimers in T cell development, we generated mice lacking expression of all of these proteins and compared their phenotype to mice lacking only zeta/eta or Fcgamma. The data reveal that surface complexes that are expressed in the absence of zeta family dimers are capable of transducing signals required for alpha/beta-T cell development. Strikingly, T cells generated in both zeta/eta-/- and zeta/eta-/--Fcgamma-/- mice exhibit a memory phenotype and elaborate interferon gamma. Finally, examination of different T cell populations reveals that zeta/eta and Fcgamma have distinct expression patterns that correlate with their thymus dependency. A possible function for the differential expression of zeta family proteins may be to impart distinctive signaling properties to TCR complexes expressed on specific T cell populations.

Keratinocytes and cytokine/growth factors

Cytokines are polypeptide growth factors produced by most nucleated cells in the body, including epithelial cells, keratinocytes, and Langerhans cells in the skin. Cytokines can be classified into interleukins, tumor necrosis factors, chemokines, colony-stimulating factor, interferons, and growth factors. Like classic hormones, cytokines bind to specific receptors to transmit their messages to target cells. Cytokine receptors can be divided into three cytokine receptor superfamilies: the immunoglobulin superfamily, the hematopoietin family, and the tumor necrosis factor family. Following cytokine/cytokine-receptor binding (first messenger), a signal transduction pathway is initiated. Factors affecting homeostasis in the skin and oral mucosa include a delicate balance between cytokines/cytokine-receptors and their antagonists. An imbalance in these variables can influence the development of cutaneous and oral diseases-such as lichen planus, autoimmune disorders, and some neoplastic processes- and can affect wound healing. Potential uses of cytokines include cancer and antiviral therapy.