Lymphoproliferative response as an index of cellular immunity in malignant melanoma of the uvea and its correlation with the histological features of the tumour.

Abstract

Cell-mediated immunity and immune complexes were studied in 22 cases of malignant melanoma of the choroid and in 3 patients with iris melanoma. An attempt was made to correlate the cell-madiated immunological changes with the histological features of the tumor and the extent of the disease. In most of the patients the lymphoblastic response to tuberculin and phytohemagglutinin was within normal range, indicating that there is no obvious suppression of T lymphocyte-dependent immunity in intraocular melanoma. However, only .apprx. 1/2 the patients showed an increased lymphoproliferative response to their own tumor antigens or to pooled allogeneic melanoma extracts. The response to the latter was invariably weaker, suggesting that although melanoma antigens may show cross-reactivity there exists an element of individual specificity. As the transformation index was generally low (.simeq. 3) it is tempting to conclude that uveal melanomas are poorly immunogenic or that the immune system is insufficiently stimulated when the tumor is confined within the eyeball. The latter seems more likely. Although the lymphocyte transformation test appears to be unreliable in the early diagnosis of intraocular melanoma, it promises to be useful in the prognosis of this tumor. The host immune system appears to be better stimulated if the tumor is large and contains a detectable proportion of epithelioid cells. Histochemical and ultrastructural examination of the lymphocytes infiltrating the tumor showed evidence of cytoplasmic activation, suggesting that these cells may be actively engaged in tumor homoeostasis. With 1 exception C1q[q fragment of complement component 1]-binding immune complexes were not raised in the blood of the patients examined so that tumor-enhancement (through this mechanism at least) may not be an important feature in the natural history of intraocular melanoma.