Cell adhesion molecule expression in the sheep thymus

Cell adhesion molecules are potential regulating factors in both prethymic and intrathymic T cell development. An experimental challenge has been the development of a large animal model that facilitates in vivo studies of bot h intrathymic development and lymphocyte migration. To extend earlier studi es of thymic development. we have developed a panel of monoclonal antibodie s (mAb) to a variety of sheep cell adhesion molecules. Immunohistochemistry was used to define mAb reactivity and flow cytometry was used to quantify expression of cell adhesion molecules within the thymus. To facilitate Row cytometry definition of cortical thymocytes. mAbs were developed to the she ep CD1 antigen. Dual parameter Row cytometry provided a phenotypic characte rization of cell adhesion molecule expression on both CD1(+) and CD1(-) she ep thymocyte populations. These studies: demonstrated significantly enhance d cortical thymocyte expression of three cell adhesion molecules: beta1 int egrin (CD29), ICAM-2 and LFA-3. The beta1 integrin cell adhesion molecule w as also expressed at higher levels on CD1(+) thymocytes in post-natal lambs as compared to adult sheep. These studies of thymocyte membrane molecule e xpression should facilitate future investigations of sheep intrathymic deve lopment and T lymphocyte immigration. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.