Sequence analysis of rat integrin alpha(E1) and alpha(E2) subunits: tissue expression reveals phenotypic similarities between intraepithelial lymphocytes and dendritic cells in lymph

The integrin alpha(OX-62) subunit is defined by the OX-62 monoclonal antibody that was raised against rat dendritic cells in lymph (veiled cells) and shows properties similar to those of human alpha(E2) that is predominantly expressed on intraepithelial lymphocytes. To clone alpha(OX-62), rat probes generated using primers specific for the human alpha(E) sequence were used to screen rat T cell cDNA libraries. cDNA clones encoding two similar but not identical alpha subunits that are closely related to but distinct from human alpha(E) were isolated. alpha(E1) is predicted to be the rat homolog of mouse alpha(M290) and alpha(E2) corresponds to rat alpha(OX-62). Immunofluorescence analysis revealed that mouse alpha(E1) and rat alpha(E2) are expressed in dendritic epidermal T cells in the skin, intraepithelial lymphocytes in the small intestine and in cells with a dendritic morphology present at sites where gamma delta T cells occur in lymphoid organs. Unexpectedly, alpha(E2) is co-expressed with intracellular CD3-delta and a 33-kDa CD3 chain but not the T cell receptor in veiled cells. These findings suggest that veiled cells may be derived from a lymphoid precursor. Furthermore, veiled cells show phenotypic similarities to intraepithelial lymphocytes.