IL-12 GENE-EXPRESSION IN HUMAN SKIN-DERIVED CD1A(+) DENDRITIC LYMPH CELLS

Recent reports point to a role for interleukin-12 (IL-12) in regulatin g T- and NK-cell function, macrophage activation and initiation of Th1 -type cell responses, We sought to determine whether CD1a(+) dendritic cells of the skin, as major antigen-presenting cells, are a source of IL-12 and therefore important in the initiation of Th1-type cell resp onses, To investigate this hypothesis, we cannulated microsurgically a skin-draining lymph vessel in the lower legs of five healthy voluntee rs, Altogether, ten different samples, each consisting of 1 x 10(6) ly mph cells, were investigated, In four of the ten samples, CD1a(+) dend ritic lymph cells were isolated and purified by positive selection usi ng mouse anti-CD1a monoclonal antibodies and sheep anti-mouse antibody -coated Dynabeads, Messenger RNA levels were estimated using a nested reverse transcriptase polymerase chain reaction (nRT-PCR) method, Tota l RNA was extracted from the cells, reverse transcribed to cDNA and am plified using specific primers for the target gene, Amplified products were sized by electrophoresis and visualized by ethidium bromide, Exp ression of IL-12 p40 and p35 mRNA was detected in all samples, both wh ole lymph samples and the highly enriched CD1a(+) dendritic cell popul ation, Our findings demonstrate that human skin-derived CD1a(+) dendri tic lymph cells produce IL-12 mRNA and may therefore be an important s ource of IL-12. Thus one might speculate that these CD1a(+) dendritic cells, through their IL-12-producing capacity, might significantly inf luence the balance of Th1 versus Th2 reactions ultimately occurring.