GM-CSF mRNA and protein in human skin-derived lymph

GM-CSF together with IL-1 beta and TNF-alpha has been shown to play a key role in the maturation of LC in vitro. To investigate the presence of GM-CSF, IL-1 beta and TNF-alpha in human skin-derived lymph, we cannulated microsurgically a superficial lymph vessel on the lower leg of six healthy volunteers. Messenger RNA levels were estimated by a reverse transcriptase polymerase chain reaction (RT-PCR) method. From a total of 20 different samples, each consisting of 10(6) lymph cells, total RNA was extracted, reverse transcribed to cDNA and amplified using specific primers for the target gene. Amplified products were sized by electrophoresis and visualized by ethidium bromide. Specific transcripts for GM-CSF were detected in all lymph samples, indicating that circulating human skin-derived lymph cells express GM-CSF mRNA. A mean level of 11.5 +/- 2.1 pg/ml GM-CSF was detected in the lymph samples examined, as determined by a sensitive ELISA. In contrast to GM-CSF, occasional weak mRNA signals together with a mean level of 2.7 +/- 2.2 pg/ml were found for IL-1 beta, and neither specific transcripts nor protein were detected for TNF-alpha. Thus, our results demonstrate that afferent skin lymph cells constitutively express GM-CSF.