EFFECTS OF CIS-UROCANIC AND TRANS-UROCANIC ACIDS ON THE SECRETION OF INTERLEUKIN-1-BETA AND TUMOR-NECROSIS-FACTOR-ALPHA BY HUMAN PERIPHERAL-BLOOD MONOCYTES

In order to investigate the mechanism of urocanic acid (UCA)-mediated immune modulation, we studied the effect of cis- and trans-UCA on inte rleukin-1 beta and tumour necrosis factor-alpha production by human pe ripheral blood monocytes, using immunospecific ELISA techniques. Trans -UCA augmented the interleukin-1 beta production and inhibited tumour necrosis factor-alpha production in a dose-dependent manner, whereas c is-UCA had no effect on the secretion of these cytokines by phorbol my ristate acetate or lipopolysaccharide-stimulated monocytes. This is a novel example of trans-UCA mediating a biological effect, a finding ea rlier reported for cyclic adenosine monophosphate up-regulation in hum an fibroblasts by Palaszynski and coworkers and for human natural kill er cell inhibition by ourselves. Our data suggest an important role fo r trans-UCA as an immunomodulator in the skin.