Studies with a monoclonal antibody on the distribution of Thy-1 in the lymphoid and extracellular connective tissues of the dog.

BALB/c mice were immunized with canine T lymphocytes from lymph node and used in cell fusion experiments to derive monoclonal antibodies to the T lymphocyte surface. The cloned hybrid line F3-20-7 described in this paper was shown to be secreting antibodies directed at canine Thy-1 since (1) the tissue distribution of the antigen corresponded precisely to the tissue distribution expected of canine Thy-1 from previous studies and (2) the antigen purified from F3-20-7 monoclonal antibody affinity columns (a) had the same mobility on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) as pure rat Thy-1 and (b) could inhibit and assay shown previously to be directed at canine Thy-1 on the basis of cross-reactivity with rat Thy-1. Studies with the fluorescence-activated cell sorter showed that all thymocytes and lymph node T lymphocytes of the dog were Thy-1 positive, establishing that Thy-1 is a T cell marker in the dog, as in the mouse, although the presence of a small percentage of Thy-1-positive B cells could not be entirely excluded. In addition, 15% of the nucleated bone marrow cells were Thy-1 positive, which is similar to the finding in rat bone marrow. Localization studies on frozen sections of skin demonstrated large amounts of Thy-1 organized in a highly structured manner around the basal parts of the hair follicles. This covering of Thy-1 was lost as the follicles approached the surface. Epidermal cells were Thy-1 negative. In the kidney, Thy-1 was shown to be strongly associated with all of the basement membranes of the medulla. The kidney cortex, including glomeruli was essentially negative, except for the occasional staining of basement membranes, possibly of collecting ducts.