Human afferent lymph from normal skin contains an increased number of mainly memory / effector CD4(+) T cells expressing activation, adhesion and co-stimulatory molecules.

We investigated the T cell population in the afferent lymph and the peripheral blood with regard to expression of activation, adhesion and co-stimulatory molecules and cytokine profile by immunohistochemistry and flow cytometry. The majority of the lymphoid cell population in the afferent lymph were CD4(+), CD45RO(+) T cells expressing the alpha beta TCR. An increased percentage of the T cells expressed activation molecules like HLA-DR, CD25, CD26, CD69 as well as adhesion and co-stimulatory molecules like CD54, CD154 / 40 ligand. Furthermore, T cells in the afferent lymph predominantly expressed the type 1 cytokine IFN-gamma, whereas type 2 cytokines such as IL-4, IL-5, IL-10 were not or barely detectable. Interestingly, dendritic cells expressing IL-12 were also found in close association with some lymphocytes, indicating that these contacts may be important in promoting Th 1 cells. In conclusion, an increased number of mainly CD4(+) memory / effector T cells, expressing activation, adhesion and co-stimulatory molecules migrate through the afferent skin-derived lymph in humans. Furthermore, our data demonstrate the dominance of a type 1 cytokine profile in these T cells and suggest that they have an important function in the immune surveillance against pathogens or other antigens in the skin and its associated lymphoid tissue.