Melanoma cells are unusual because, unlike most epithelial tumours, constit
utive expression of HLA class II antigens is common. We have previously dem
onstrated that a peptide-specific CD4+ 7-cell clone proliferates briskly in
response to peptide and HLA class II expressing melanoma cell lines derive
d from metastases. Here we demonstrate that these CD4+ T-cells secrete larg
e amounts of interferon-gamma (IFN gamma) and interleukin-10 (IL10), and in
significant quantities of IL2 or IL4, in response to peptide presentation b
y both melanoma and autologous B-cells. T-cells produced more IL10 when res
ponding to peptide presentation by melanoma cells compared with B-cells, an
d less IFN gamma (P<0.01). Addition of IL12 did not alter the cytokines pro
duced but increased the T-cell production of both, especially the productio
n of IL10 in response to peptide presentation by melanoma cells. Our data s
uggest that differential cytokine production by CD4+ T-cells in response to
peptide presentation by HLA class II expressing tumour cells may contribut
e to tolerance to tumour antigens. (C) 1999 Lippincott Williams & Wilkins.