Occurrence of Ia antigens on tissues of non-lymphoid origin

Abstract

UNLIKE the classical transplantation antigens, called HLA-A,B,C in man and H-2K,D in mouse, the HLA-DR (la) antigens have a restricted tissue distribution¹. Primarily cells belonging to the immune system express Ia antigens whose only known biological role is to participate in cell-to-cell cooperation events involving lymphocytes and macrophages^2–4. However, cells of the immune system do not only interact among themselves but they also associate physically with other types of cells like epithelial cells of the intestine and the lactating mammary gland⁵ and with reticuloepithelial cells of the thymus⁶. The possibility that all such interactions are under la antigen control is raised by indirect immunofluorescence analyses which show that la antigens are expressed on a great variety of epithelia. We report here our examination of several cryostat sections of guinea pig tissues for the presence of la antigens by indirect immunofluorescence. To obtain staining patterns that were reproducible and significantly different from the controls it proved necessary to use immunosorbent-purified heteroantibodies (see legend to Fig. 1 for description of the antibodies).