Polyclonal antibodies against human melanocortin MC1 receptor: preliminary immunohistochemical localisation of melanocortin MC1 receptor to malignant melanoma cells.

Peptides of 11 and 15 residue lengths were synthesised according to the sequence of the N-terminal region of the human MC1 melanocyte stimulating hormone receptor. The peptides were conjugated to thyroglobulin and used for preparation of antisera in the rabbit. Each of the conjugates raised antisera which showed high titre and specificity for its respective peptide antigen when evaluated in an ELISA test. Both types of antisera immunostained MC1 receptor expressing COS-7 cells. By contrast, the sera did not stain control COS-7 cells not expressing the MC1 receptor. Moreover, preimmune sera or antiserum preadsorbed with its respective peptide did not stain the MC1 receptor expressing cells. The antisera were used to immunostain sections of normal human skin, as well as samples of cutaneous malignant melanoma tumours obtained from a patient. The cells of the melanoma tumours were very strongly immunostained with the MC1 receptor antisera. By contrast, melanocytes which were present in the normal skin could not be visualised with our antisera.