Using monoclonal antibodies and fluorescence-activated cell cytometry, the expression of integrins on the surface of B and T lymphocytes isolated from normal (n = 10), UC (n = 8), and CD (n = 11) tissues was assessed. Anti-CD8 and anti-CD19 were used to “gate” T and B lymphocytes, respectively. B cells from UC and CD exhibited increased frequency of integrin α2, α5 (and in CD α6) in association with decrease in integrins α4 and β7. High levels of β1 integrin were present in all groups. Among lamina propria T-cells from a small number of specimens, UC-derived cells showed increased expression of α2 and α6 (with decreased a4) compared with both CD or normal. Comment: Although the lamina propria of the normal intestine contains a scattered assortment of monocytes and lymphocytes, the vast number of these and other leukocyte populations associated with acute inflammatory bowel disease are necessarily...