Expression and regulation of β7(βp) integrins on mouse lymphocytes: Relevance to the mucosal immune system

Abstract

A mouse lymphocyte surface molecule which is selectively expressed by mucosal T cells and detected with the monoclonal antibody (mAb) M290 has provisionally been identified as a β₇ integrin. Identification was based on close homology of its β subunit at the N terminus with the recently reported, highly distinctive, human β₇ sequence. mAb were prepared against the β and α subunits of the mouse molecule, termed β₇ and α_M290, respectively, and used to study surface expression of the two components. β₇ was present on most lymph node lymphocytes in association with α₄ rather than α_M290. This integrin, β₇α₄, was shown to be identical to LPAM-1 (βpα₄) the Peyer's patch homing receptor. Stimulation in vitro of mouse lymph node T cells with anti-CD3 in the presence of transforming growth factor (TGF)-β increased β₇ expression in about 40% of cells and changed the associated α chain from α₄ to the novel α_M290 subunit, which, in most cells, was expressed de novo. Immunoprecipitation of β₇ both from these cells and from intraepithelial lymphocytes gave closely similar results and showed predominance of the β₇α_M290 integrin. It is suggested that in vivo this change in α-chain usage occurs in mucosal T cells in response to TGF-β acting in the mucosal microen-vironment and that the new integrin confers particular adhesive properties, possibly homing specificity, on the cells.