[Phenotypic and functional analysis of thymic nurse cell (TNC)-lymphocytes]

Thymic nurse cells (TNC) are epithelial cells containing intact T-cells engulfed within membrane-lined vacuoles in their cytoplasm. Since thymic epithelial cells strongly express MHC class I and II antigens, these lymphoid-epithelial complexes have been considered to provide an optimal micro-environment for the process of self-recognition and/or clonal deactivation of thymocytes. The present experiments were designed to further analyze the phenotypical stage of differentiation and the functional properties of intra-TNC lymphocytes (TNC-L) at a single cell level using the chorionallantoic membrane (CAM) assay, which can only be performed in avian species and, thus, presents a unique possibility to circumvent technical problems for the functional study of TNC-L in mammals. In immunofluorescence analyses with monoclonal antibodies (mAb) to the chicken alpha/beta and gamma/delta T cell receptors (TCR) and the CD3, CD4, and CD8 equivalents, an enrichment was found of CD3+/CD4+/CD8-, CD3+/CD4-/CD8+, TCR alpha/beta + and TCR gamma/delta + cells inside TNC, as compared with extra-TNC thymocytes. Assessing micromanipulated, single chicken TNC in the CAM assay, we also demonstrated at a clonal level that TNC-L possess a strong graft-versus-host (GvH) reactivity in allogeneic combinations. This reaction showed morphological, phenotypical and functional characteristics of a classical graft-versus-host reaction (GvHR). The efficiency to induce a GvHR was higher for TNC-L than peripheral blood lymphocytes (PBL) or thymocytes from the same donor. Surprisingly, in syngeneic combinations TNC-L also react against self-MHC molecules with high frequency. The frequency in syngeneic combinations is, however, lower than in allogeneic combinations.(ABSTRACT TRUNCATED AT 250 WORDS)