title: Restricted expression of CD2 among subsets of sheep thymocytes and T lymphocytes.
abstract: A monoclonal antibody (mAb) generated against sheep T-cell blasts, called I/35 A, blocks sheep autologous E rosetting and competes with purified T11 target structure (TS), the sheep form of LFA3, for binding sites on the sheep T-cell surface. Immunoprecipitation from lysates of surface iodinated sheep T cells identifies the cell surface molecule recognized by mAb I/35 A as a single chain polypeptide migrating as a diffuse band of MW 55,000. From its binding properties and the biochemical nature of the target antigen, we conclude that mAb I/35 A is directed at sheep CD2. This finding makes sheep the first animal model in which the CD2-LFA3 (T11TS) system is defined by mAbs to both receptor and ligand. When analysed by two-colour flow cytometry and by immunohistochemistry, the cellular expression of CD2 in sheep differs significantly to that reported in humans. In peripheral blood, CD2 is found exclusively on CD4+8- and CD4-8+ T cells, while the third, CD4-8- (predominantly SBU-T19+) subset of sheep T cells (around 20% in peripheral blood) is CD2-. In thymus, only low to moderate levels of CD2 expression occurs on 80% of cells. Among these, medullary 'single positive' thymocytes express the highest level of CD2, whereas the CD4-8- 'double negative' population (which in contrast to peripheral CD4-8- T cells contains only very few SBU-T19+ cells) consists of CD2- and weakly positive cells. In peripheral lymphoid organs, CD2+ lymphocytes occur in the T-cell regions of spleen, lymph nodes and jejunal Peyer's patches (JPP). Tissue macrophages found in B-cell follicles of lymph nodes and JPP are also CD2+. The implications of these findings are discussed in terms of the role CD2 plays in the proliferation of immature thymocytes and of the possible importance of CD2/LFA3 interactions in lymphocyte recirculation.
authors.affiliation: Genzentrum der Ludwig-Maximilians-Universität München, Martinsried, FRG.
authors.forename: G W
authors.initials: GW
authors.lastname: Giegerich
authors.forename: W R
authors.initials: WR
authors.lastname: Hein
authors.forename: M
authors.initials: M
authors.lastname: Miyasaka
authors.forename: G
authors.initials: G
authors.lastname: Tiefenthaler
authors.forename: T
authors.initials: T
authors.lastname: Hünig
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis*; D018801:CD2 Antigens; D008562:Membrane Glycoproteins / Q000032:analysis; D011971:Receptors, Immunologic / Q000032:analysis*; D012756:Sheep; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology*
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D018801:CD2 Antigens; D008562:Membrane Glycoproteins; D011971:Receptors, Immunologic