Tumor necrosis factor-A expression in human primary malignant melanoma and its relationship to tumor infiltration by CD3+ cells

Optimal conditions for immunohistochemical staining of tumor necrosis factor-A (TNF-A) in paraffin-embedded tissue sections were established to investigate TNF-A expression in human primary malignant melanomas. Seventeen malignant melanomas of the nodular (NMM) and superficially spreading (SSM) subtypes were analyzed. Twelve of these were TNF-A⁺, while 5 did not stain for the cytokine. To evaluate how TNF-A expression affected the immune response to the tumors, infiltration by CD3⁺ and mac387⁺ cells was investigated in NMM. TNF-A expression seemed to selectively affect the capability of T cells to infiltrate the tumors since TNF-A⁺ tumors were found to have significantly lower levels of infiltrating CD3⁺ cells, while there was no difference in numbers of mac387⁺ cells. These results demonstrate that TNF-A is variably expressed in primary malignant melanoma in vivo and that the T-cell response to TNF-A-expressing NMM is inhibited. © 1996 Wiley-Liss, Inc.