Recipients of β₇^-/- T cells have significantly lower numbers of T cells in their intestinal mucosa but significantly higher numbers of circulating T cells. (A) Lethally irradiated (1300 cGy) B10.BR mice underwent transplantation such that each mouse received WT TCD-BM (5 × 10⁶) and WT (Thy1.1) T cells in combination with β₇^-/- (Thy1.2) T cells (2 × 10⁶ of each type). T cells were analyzed before transfer into recipient mice to ascertain that equivalent percentages of CD4⁺/CD8⁺ cells were being given (not shown). Mice were killed at day 8, and T cells were isolated and analyzed, as described in “Materials and methods.” Donor origin of the isolated T cells was determined by multicolor flow cytometry. Statistical analysis is as follows: for mesenteric lymph nodes and spleen, P < .001; for gut, P = .004 (n = 5); experiment repeated 3 times. (B) Lethally irradiated (1300 cGy) B10.BR recipients underwent transplantation with 5 × 10⁶ WT TCD-BM and either 1 × 10⁶ WT or β₇^-/- splenic T cells. Cardiac puncture to obtain blood for complete blood counts was performed on day 7 and day 14. ^*P ≤ .05 (n = 8).