Article Abstract:
An alternative model of thymocyte selection different from the currently accepted instructive model is discussed. The instructive model postulates that an immature thymocyte differentiates into a CD4+ helper or CD8+ cytotoxic cell depending on its receptor specificity for MHC class II or I, respectively. However, a population of CD4+ cells in MHC class II-deficient animals with thymocytes intermediate in maturity between CD4+CD8+ and endstage CD4+CD8- thymocytes are found. Thus, a selective model for thymocyte differentiation is proposed that involves two T cell receptor-MHC molecule engagements.
User Contributions:
Comment about this article or add new information about this topic:
Article Abstract:
Thymocytes differentiate into mature CD4 helper or CD8 cytotoxic cells depending on their antigen receptor specificity for MHC class II or I molecules, respectively. The CD8 differentiation and maturity pathway was analyzed using transgenic mouse systems. Results show that constitutive expression of CD4 can rescue development of mature CD8 class II reactive T cells even in mice that lack the capacity to develop CD8 cells. These results suggest a selection or stochastic mechanism of T cell differentiation.
User Contributions:
Comment about this article or add new information about this topic:
Article Abstract:
The death of pancreatic islet beta cells has been recognized as a hallmark of autoimmune diabetes. One of the general mechanisms by which cytotoxicity occurs is via a recognition-link pathway in which the destruction of cells is attributed to the recognition by cytotoxic T cells of autoantigens displayed by the major histocompatibility complex. The other mechanism proposes that when beta cells and activated T cells are proximate to each other, pancreatic islet beta cell death may occur.
User Contributions:
Comment about this article or add new information about this topic: