Spontaneous T cell responses to melanoma differentiation antigens from melanoma patients and healthy subjects

The spontaneous cytotoxic T cell responses to melanoma differentiation anti gens and influenza matrix peptide were compared in 20 HLA-A2(+) melanoma pa tients and 17 healthy A2(+) individuals. Cytotoxic T lymphocyte (CTL) respo nses were determined by mixed lymphocyte peptide culture (MLPC) involving t wo stimulations of unfractionated peripheral blood lymphocytes (PBLs) with peptide in vitro. CTL responses to Melan-A 9-mer (amino acids 27-35, AAGIGI LTV) peptide were detected in 4 out of 16 normal individuals, but in none o f the melanoma patients. CTL specific for influenza matrix peptide were fre quently found in both normal individuals and melanoma patients, suggesting that generalized immune-suppression was not responsible for this difference . No significant responses were observed in either normal individuals or me lanoma patients to Melan-A 10-mer (26-35, EAAGIGILTV), two gp100 epitopes ( 280-288, YLEPGPVTA; 457-466, LLDGTATLRL) and two tyrosinase epitopes (1-9, MLLAVLYCL; 368-376, YMDGMSQV). Melan-A (27-35)-specific CTL cells generated by normal individuals and melanoma patients recognized both synthetic pept ide-pulsed T2 cells and two HbA-A2(+), Melan-A(+) melanoma cell lines (ME27 2, LAR1) in an anti,sen-specific, MHC class I restricted mariner. T cells g enerated against Melan-A 9-mer were also able to recognize Melan-A 10-mer-p ulsed target cells. Spontaneous CTL responses to Melan-A 9-mer from three k nown responder normal individuals were further evaluated over a prolonged t ime course (6-11 months). All 3 subjects demonstrated specific Melan-A 9-me r responses throughout the study period, although lytic activity fluctuated over time for a given individual. We found the MLPC assay to be reliable a nd easy to perform for monitoring T cell responses, although it may still n ot be sufficiently sensitive to detect low numbers of precursor T cells.