DETECTION OF PITYROSPORUM-ORBICULARE REACTIVE T-CELLS FROM SKIN AND BLOOD IN ATOPIC-DERMATITIS AND CHARACTERIZATION OF THEIR CYTOKINE PROFILES

Background Atopic dermatitis (AD) is associated with increased levels of serum IgE, and T-helper (Th) cells are thought to a play role in th e pathogenesis. Individuals with AD often develop IgE antibodies again st the yeast Pityrosporum orbiculare, a member of the normal cutaneous flora. Objective The role of P. orbiculare in atopic dermatitis was i nvestigated by examining the T-cell reactivity for P. orbiculare. Meth ods Freshly isolated peripheral blood mononuclear cells (PBMC) were is olated from 10 AD patients with serum IgE antibodies against P. orbicu lare, and from six healthy controls. The proliferative response after P. orbiculare stimulation, measured by [H-3]thymidine incorporation, w as examined in the PBMC and in T-cell clones (TCC) obtained from skin and blood of one patient, The cytokine profile of the TCC was determin ed by enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA ) and reverse transcriptase-polymerase chain reaction (RT-PCR) followi ng challenge with either P. orbiculare extract or anti-CD3 antibodies and phytohaemagglutinin. Results The PBMC response to P. orbiculare wa s significantly higher in the AD patients than in the control group (P < 0.05). Twenty-nine out of 36 tested TCC derived from one responding patient were reactive for P. orbiculare. The clones were CD2(+) and C D4(+), except for one CD8(+) blood clone, A majority of the TCC derive d from lesional skin showed a Th2- or Th2/Th0-like cytokine profile. A co-expression of interleukin-5 (IL-5) mRNA and IL-13 mRNA was detecte d in five out of six P. orbiculare-reactive clones analysed for their cytokine gene expression with RT-PCR. Conclusion Our data suggest that P. orbiculare can induce a T-cell response in AD patients. The Th2-li ke profile of P. orbiculare-reactive TCC derived from lesional skin in dicates that P. orbiculare may play a role in maintaining IgE-mediated skin inflammation in AD.