Rise in dermal CD11c+ dendritic cells associates with early-stage development of psoriatic lesions

There is limited information available regarding the phenotype and function of leukocytes involved in the earliest stages of psoriatic lesion development. In this study, we examined the presence of different types of leukocytes in psoriatic point lesions collected at three 1-week interval time points from a recent and simultaneously formed group of point lesions. The cells were quantified and compared with K16 expression and epidermal thickness, both typically increased in this disease and considered as hallmarks. We found a significant correlation between K16(+) cell increment and the increase in epidermal thickness in the timeframe of 14 days. The change in CD3(+), CD4(+), and CD8(+) T-cell numbers in the dermis showed a significant association with these two features from d7 to d14, whereas in the epidermis only CD8(+) T cells demonstrated a significant correlation. Remarkably, the relationship between T cells and disease progression was preceded by a significant correlation of CD11c(+) dendritic cells (DCs) with K16 expression and epidermal thickness from baseline onwards. Interestingly, there was also a numeric correlation of CD11c(+) DCs with the CD3(+) T-cell shifts from d7 to d14. A significant correlation was also found between dermal CD14(+) cells and K16 expression from d7 to d14. BDCA-2(+) plasmacytoid DCs were absent in non-lesional skin, but found at low numbers in most lesions. The change in plasmacytoid DC or neutrophil numbers did not correlate with lesion development. In conclusion, our study suggests a relevant role for T cells, and in particular dermal CD11c(+) DCs, in the earliest stage of psoriatic lesion development.