AIM: To investigate the expression and the possible implication of CD40/CD40L costimulatory molecules in erythema nodosum of patients with BehÇet's disease. METHODS: Sampling was done from erythema nodosum of 5 patients with BehÇet's disease and normal skin of 2 healthy individuals. Immunohistochemical staining was performed to examine the expression of CD4, CD8, CD19, CD68, HLA-DR, CD40 and CD40L molecules in the obtained tissues.
RESULTS: Approximately 90% of epidermic cells in erythema nodosum expressed CD40 moleculeIn the dermis and subcutaneous tissue, a significantly increased number of CD4⁺Tcells, CD8⁺Tcells, CD19⁺cells, CD68⁺cells, HLA-DR⁺cells, CD40L⁺cells, and CD40+cells were observed in the erythema nodosum as compared with that in normal skin. Double staining showed that CD40L molecules were expressed on 45% of CD4⁺ T cells. CD40 molecules were expressed on 100% CD68⁺ cells and 59.2% of HLA-DR⁺cells respectively. CONCLUSION: A number of CD40/CD40L costimulatory molecules are upregulated in the erythema nodosum of patients with BehÇet's disease.