Contact allergy to nickel: patch test score correlates with IL-5, but not with IFN-gamma nickel-specific secretion by peripheral blood lymphocytes. 
Traditionally, allergic contact dermatitis (ACD) has been associated with the activity of Th1 lymphocytes that secrete interferon gamma.  Recent evidence indicates that other cells, e.g. interleukin 5 (IL-5)-secreting Th2 or Tc2 cells may be among the key effectors of ACD.  The aim of the present study was to assess the influence of nickel-specific IFN-gamma secretion (marker of Th1 and Tc1 activity) and IL-5 secretion (Th2 and Tc2) on the clinical outcome (patch test score) in nickel-allergic patients.  40 women with suspicion of ACD were involved, aged from 14-54 (median 31.5) years.  They were patch tested with NiSO(4).  Peripheral blood mononuclear cells (PBMC) from the patients were cultured and analysed for IFN-gamma and IL-5 secretion in response to NiSO(4).  A series of statistical models (classical logit or cloglog link function) were used.  We demonstrate that nickel-specific IL-5 secretion by PBMC is correlated with the intensity of patch test reaction (p=0.05), with no significant effect of IFN-gamma.  An increase in the nickel-specific IL-5 secretion from PBMC by 10 pg/ml is associated with a 10-20% increase (depending on statistical model) in the odds ratio of the patient to have a higher patch test score.  These findings support the assumption that cells secreting IL-5 (e.g. Th2, Tc2) play a more important role in the pathogenesis of ACD than previously thought.