Langerhans cells acquire a CD8+dendritic cell phenotype on maturation by CD40 ligation

Dendritic cell (DC) reconstitution experiments and phenotypic analysis of D C subpopulations have allowed the definition in the mouse of two main DC ca tegories: CD8(+) lymphoid DCs and CD8(-) myeloid DCs, With regard to Langer hans cells (LCs), which represent immature DCs differentiating into mature DCs on migration to the lymph nodes after an antigenic stimulation, althoug h classically considered as myeloid DCs, there is no experimental evidence of their origin. It has been recently shown that mouse LCs, negative for CD 8 and LFA-1, undergo CD8/LFA-1 up-regulation on migration, suggesting that LCs belong to the CD8(+) lymphoid DC lineage. To further reinforce this hyp othesis, we have analyzed the modulation of CD8 expression by LCs on cultur e with molecules known to induce LC maturation. Our results show that LC ac quired a CD8(+) lymphoid phenotype on CD40 ligation.