A novel antigen is common to the dome epithelium of gut- and bronchus-associated lymphoid tissues.

The dome epithelium (DE) covering bronchus- and gut-associated lymphoid tissues (BALT and GALT) is composed of columnar cells, groups of lymphocytes, M cells, and pre-M cells. Although the cell biology and immunologic processes of this tissue are likely important in the afferent arm of secretory immune responses, virtually nothing is known about biochemical constituents of the DE. Therefore, a monoclonal antibody, 30E5, was used to study the distribution of a novel antigen, common to dome epithelia of GALT and BALT. 30E5 was secreted by a hybridoma, prepared by fusing murine splenocytes, immunized against dome epithelial cells, with P3 X 68/Ag8 myeloma cells. Reactivity of antigens was defined by indirect immunocytochemistry on sections of rabbit tissues or with dissociated epithelial cells. In situ, 30E5-reactive antigen circumscribed each group of dome epithelial lymphocytes, most or all of which were T cells, in rabbit appendix, sacculus rotundus, cecal patch, Peyer's patch, and BALT. In the DE this antigen was associated with the apical surface and the supranuclear or perinuclear regions of epithelial cells, but it was not associated with epithelial cells of villi, epithelium, or with individual lymphocytes. In peripheral lymph nodes, spleen, and in domes and follicles of GALT or BALT, 30E5-reactive antigen was visualized in linear wisps, primarily in regions populated by thymocytes. In other adult tissues, 30E5-reactive antigen was associated with involuntary muscle, myoepithelial cells of lactating mammary gland and with what appeared to be neural dendrites; but it was not found in epithelia other than DE. In neonatal rabbit appendix, this antigen first appeared in the upper dome epithelium two days after birth, a period coinciding with T cell infiltration and M cell maturation. The histologic distribution of 30E5-reactive antigen suggested that it might be a contractile filament, a receptor, or a differentiation antigen. Since 30E5 was associated with DE of both GALT and BALT, results support the concept of a molecule common to all mucosa-associated lymphoid tissues.