The Immune Reaction Against Malignant Melanoma Studied in a Biopsy Material

Biopsies from primary and secondary malignant melanomas have been studied by light microscopy as well as by fluorescence and electron microscopy. In the two primary tumours, lymphocytes in different stages of transformation were observed at the periphery of the tumour, but evidence of a cytotoxic effect of the immune cells against the tumour cells could not be obtained. Plasma cells were few and deposits of γ‐globulins were not observed outside these cells. In 13 of the 15 metastatic tumours, lymphocytes and plasma cells were observed among the tumour cells, the latter being the most prevalent cell type. In 11 patients, γ‐globulins were found on the surface of the tumour cells and in 7, a variable proportion of the cells showed specific cytoplasmic fluorescence. In one tumour, ultrastructural changes, interpreted as changes due to immune cytolysis, were observed. Viruslike particles were not observed in any case.