WHIM-mutant CXCR4 impairs T-DC interactions in ex vivo lymph node slice cultures. DCs were either cognate antigen-pulsed (OVA) or unpulsed (no pept). (A) Duration of T-DC interactions within ex vivo lymph node slices imaged by 2-photon microscopy. The summary results of 2 videos per condition are shown. Each dot represents a single T-DC interaction (from left to right, n = 125, 101, 66, 21, 298, 291, 197, and 183). An independent experiment with the T-cell populations labeled with different dyes yielded the same result. A Fisher’s exact test was applied to the number of interactions ≥20 minutes versus the number of interactions <20 minutes. *P < .05; **P < .01; ***P < .001. (B) The percentage of T-DC interactions ≥20 minutes, out of all analyzed interactions. White bars indicate nonretrogenic OVA-specific control T cells; gray bars indicate OVA-specific T cells retrogenically expressing WT CXCR4; black bars indicate OVA-specific T cells retrogenically expressing WHIM-mutant CXCR4. The statistical analysis refers to the Fisher’s exact test, as in (A). ctrl, nonretrogenic OVA-specific T cells; WT, OVA-specific T cells retrogenically expressing WT CXCR4; WHIM, OVA-specific T cells retrogenically expressing WHIM-mutant CXCR4. See also supplemental Videos 1-5. n.s., not significant.