In vivo homing of T lymphocytes. Equal numbers of differentially labeled cells were mixed and injected into C57BL/6J-CD45.1⁺ congenic recipient mice. The number of homed donor cells and homing indices were determined 2 hours after injection. Data are expressed as the mean values ± SEM. Two-tailed Student t test was used for statistical analyses. Statistical significance was defined as *P < .05, **P < .01, or ***P < .001 vs SP. SP indicates spleen; PBL, peripheral blood lymphocytes; PLN, peripheral lymph node; MLN, mesenteric lymph node; PP, Peyer patch; SI, small intestine; LI, large intestine; BM, bone marrow; LIV, liver; and LUN, lung.