Mice Lacking Expression of Secondary Lymphoid Organ Chemokine Have Defects in Lymphocyte Homing and Dendritic Cell Localization

Gunn, Michael D.; Kyuwa, Shigeru; Tam, Carmen; Kakiuchi, Terutaka; Matsuzawa, Akio; Williams, Lewis T.; Nakano, Hideki

Decreased Migration of DCs into T Cell Zones of plt Mice. Interdigitating DCs in the T cell zones of LNs arise from DCs in the periphery which migrate to this area via the lymph after activation. To determine if the paucity of interdigitating cells observed in plt mice was due to a defect in the migration of DCs to LNs, we examined this migration after contact sensitization. 24 h after skin painting with 2 mg FITC, the frequency of FITC ϩ cells in the draining LNs of plt mice was markedly reduced compared with ϩ/ϩ mice (Fig. 4 A) . The identity of these cells as DCs was confirmed by their characteristic forward and side scatter profiles, their staining with anti-CD11c (Fig. 4 B) and anti-I-A (Fig. 4 C) , and their low buoyant density. A comparison of eight FITC-painted plt mice with controls at 24 h revealed a 75% decrease in the number of FITC ϩ DCs in draining LNs (Fig. 4 D) . To ensure that the FITC signal in draining LNs was due to the migration of DCs rather than FITC accumulation within the LNs, we performed unilateral contact sensitization with low dose (0.2 mg) FITC and compared contralat-eral and draining LNs. In this procedure, resident (FITC Ϫ ) DCs can be distinguished from newly migrated (FITC ϩ ) DCs (35) . 24 h after skin painting, contralateral and draining LNs contained similar numbers of FITC Ϫ DCs in both ϩ/ϩ and plt mice (Fig. 4 E) . Similar to results shown above, the number of resident DCs was decreased 60% in plt mice. The draining LNs of painted mice demonstrated accumulation of FITC ϩ I-A ϩ cells. In plt mice, the number of these newly migrated FITC ϩ DCs was decreased 73% compared with ϩ/ϩ mice (29.5 Ϯ 11 ϫ 10 3 vs. 8.1 Ϯ 5.7 ϫ 10 3 , P ϭ 0.011, n ϭ 5).