Expression of the CD40 antigen on normal endothelial cells and in benign and malignant tumours of vascular origin.

CD40, a member of the nerve growth factor/tumour necrosis factor-receptor family, is expressed on endothelial cells in situ and in tissue culture. It is functionally involved in the regulation of the expression of adhesion molecules in these cells. In the current study we investigated the expression of CD40 on the endothelia of normal fetal and adult human tissues, as well as in the stroma of various neoplasms and in different inflammatory tissue reactions. By immunohistochemistry, endothelia were negative or only weakly positive for CD40 in all normal adult and most fetal organs studied. In contrast, endothelial cells of fetal and embryonic lungs, kidneys and larger vessels consistently expressed the CD40 antigen. Strong expression of CD40 on endothelial cells of blood vessels but not of lymphatic vessels was found in inflammatory reactions. In 65 tumours of vascular origin we found moderate to strong expression of CD40 in all of four juvenile proliferating capillary haemangiomas and 11 lobular capillary haemangiomas of adults. Senile and cavernous haemangiomas as well as lymphangiomas were negative or exhibited only weak CD40 reactivity. Weak to moderate CD40 expression was found in five of eight malignant neoplasms of endothelial origin. Our finding that the CD40 antigen is present on only a minority of normal endothelial cells, whereas strong staining can be detected on the majority of endothelial cells in inflammatory processes, complements previous reports which suggest that this surface receptor plays an important role in tissue inflammation. The heterogeneous pattern of expression in malignant endothelial neoplasms argues against a major role for CD40 in the pathogenesis of these tumours. Its consistent presence in juvenile and lobular capillary haemangiomas suggests rather the involvement of CD40 in the development and/or progression of these benign vascular proliferations.