Distribution of α4β7 and αEβ7 integrins on thymocytes,intestinal epithelial lymphocytes and peripheral lymphocytes

β₇ is expressed on subsets of thymocytes, while T and B lymphocytes show heterogeneous expression of β₇. Here, we examine the phenotype of the thymocyte and lymphocyte subsets which express α₄β₇ and α_Eβ₇ using mAb against α_Eβ₇ and mAb DATK32 which recognizes a combinatorial epitope on α₄β₇. β₇⁺ thymocytes have a mature phenotype: TcR⁺, CD11a^hi CD44^hi HSA^dull. Small subsets of double-negative CD4_?CD8_?, single-positive CD4⁺ and CD8⁺ thymocytes express α₇, while double-positive CD4⁺ CD8⁺ thymocytes are β₇. However, two integrins α_Eβ₇ and α₄β₇ recognized by anti-β₇ are not expressed on an identical subpopulation of thymocytes, as β_Eα₇⁺α₄β₇^?, α_Eβ₇⁺α₄β₇⁺ and α_Eβ₇^?α₄β₇⁺ thymocyte subsets are evident. Similarly, intraepithelial lymphocytes express high levels of α_Eβ₇ but little α₄β₇. In the spleen, Peyer's patches and lymph nodes, α₄β₇ is expressed at higher levels on most B lymphocytes than on the majority of T lymphocytes, while a small subset of T lymphocytes, which includes both CD4⁺ and CD8⁺ lymphocytes, express high levels of β₇ in the form of α₄β₇ and α_Eβ₇, although, as observed with lymphocytes, not all α₄β₇^hi CD4^? lymphocytes expressed α₄β₇. The population of α₄β₇^hi CD4 lymphocytes are enriched in Peyer's patches and form subsets of the memory CD4⁺ lymphocyte population, which can be further subdivided on the basis of α_Eβ₇, L-selectin and α₄ expression. Therefore, memory CD4⁺ lymphocytes are highly heterogeneous in their expression of adhesion receptors, and presumably these subpopulations will exhibit very different trafficking properties.