Impaired migration of WASp-null skin DCs to LNs following contact sensitization with FITC. Normal and WASp-null mice were painted with FITC, after which single-cell suspensions of draining LNs were prepared at 4 hours and 18 hours before analysis by flow cytometry. (A) Flow cytometry detects, 4 hours after sensitization, a small but higher percentage of I-A^b+/FITC⁺ cells (right quadrant) in normal (WT, top row) compared with mutant (WASp-null, bottom row) LNs. Consistently, at 18 hours after sensitization, a higher number of I-A^b+/FITC⁺ cells (right quadrant) are found in normal LNs; in contrast, WASp-null I-A^b+/FITC⁺ showed a more variable response. The identity of a small population of I-A^b–/FITC⁺ cells was not determined. This panel represents 1 experiment of 7. (B) Chart shows pooled data of 7 experiments for each group, where each symbol represents a single mouse. A greater percentage of I-A^b+/FITC⁺ immigrants was found in normal (WT, ▪) compared with mutant (WASp-null, ▴) LNs (*P < .05; Mann-Whitney test) at 4 hours after sensitization only. Horizontal bars indicate the mean.