In an immunocytochemical study involving fine needle aspirates from 21 patients with systemic metastatic malignant melanoma studied before initiation of IFN-α treatment, 10 out of 11 patients with moderate to high numbers of infiltrating CD4+ lymphocytes achieved tumor regression, while 9 out of 10 patients with low numbers of these cells had progressive disease. This evidence concerns the gene IFNA1 and metastatic melanoma.