Expression of the human OX40 (hOX40) antigen in normal and neoplastic tissues

Summary. The Ber-ACT35 mAb was raised against the human T-cell lymphotrophic virus (HTLV) 1-transformed, CD4⁺ HUT 102 cell line and recognizes the human homologue of the 0X40 (hOX40) antigen. The analysis of the expression of hOX40 by immunohistochernical techniques in malignant lymphomas, carcinomas and non-malignant tissues of different organs shows that hOX40 expression was almost completely restricted to T lymphocytes. Besides T cells only a small subpopulation of macrophages in Langerhans'cell histiocytosis and a few blasts in B-cell non-Hodgkin's lymphoma (B-NHL) revealed a faint immunostaining with the Ber-ACT35 mAb. Furthermore, most of the hOX40⁺ T-cells are CD4⁺.