Biology of interleukin-5 in ocular cicatricial pemphigoid

Background: Ocular cicatricial pemphigoid (OCP) is an autoimmune disease characterized by the presence of autoantibodies, T-cell dysregulation, and abnormal serum levels of cytokines such as interleukin-6, interieukin-1, and tumor necrosis factor-alpha. The purpose of the present study was to investigate levels of interleukin-5 (IL-5) in the sera, eosinophil counts in the peripheral blood, and eosinophil and mast cell counts in the inflamed conjunctivae of patients with active OCP. Methods: Seven patients diagnosed in the active phase of OCP presenting with chronic cicatrizing conjunctivitis were studied. The serum levels of IL-5 were compared to a group of seven age-, race-, and sex-matched normal human subjects. Eosinophil and mast cell counts in the patients' conjunctivae were compared to those in normal conjunctivae harvested during cataract surgery from seven normal individuals. In addition, eosinophil counts in peripheral blood of patients with active OCP were compared to those in normal individuals. Results: The mean serum level of IL-5 in patients with active OCP was higher (67.23 pg/ml, range 46.33-98.26 pg/ml) than that in normal individuals (12.18 pg/ml, range 7.66-18.86). The difference was statistically significant (P<0.001). On light microscopy the biopsied conjunctivae stained with hematoxylin and eosin revealed statistically significant differences (P<0.001) in the mean numbers of eosinophils in the substantia propria between the patients with active OCP (6.8 cells/cm(2), range 4.8-8.2 cells/cm(2)) and normal controls (0.91 cells/cm(2), range 0.4-1.8 cells/cm2). The average number of mast cells found in the substantia propria of the biopsied conjunctivae was statistically significantly higher in patients with OCP (13.79 cells/cm(2), range 6.6-19.4) than in normal individuals (4.34 cells/cm(2), range 3.2-7.8; P<0.01). The average number of eosinophils in the peripheral blood of patients with active OCP (6.6x10(7)/1, range 2.9 - 9.3x10(7)/1) was statistically significantly higher (P<0.01) than in normal controls (2.09x10(7)/1, range 0 - 4.5x10(7)/1). The results suggest that IL-5 may play an important role in the pathogenesis of OCP.