beta(1) integrins are not required for the maintenance of lymphocytes within intestinal epithelia.

b1 integrins are thought to play a central role in maintaining lymphocytes within mucosal epithelia via their interactions with extracellular matrix proteins and subepithelial cellular components within and underlying the basement membrane. In the current study type a (CD8abTCRab) and type b (CD8aaTCRcd and CD8aaTCRab) intraepithelial lymphocyte (IEL) subsets within the mouse small intestine were found to express functional b1 integrin and the b1 integrin a chain partners a1, a2, and a4. Using inducible b1 integrin-knockout bone marrow-chimeric mice we demonstrate that IEL expression of a1 and a2 but not a4 is dependent on expression of the b1 chain. Importantly, deletion of the b1 chain in IEL did not alter the number or composition of lymphocytes within the intestinal epithelium. Thus, while IEL express functional b1 integrins, these are not required to maintain lymphocytes within intestinal epithelia. This result is discussed in the light of conventional views of intestinal lymphocyte homing and localization. (Less)