Effect of epidermal Langerhans cells from melanoma patients on lymphoproliferative responses

Langerhans cells (LC) are potent antigen-presenting dendritic cells essential for cutaneous immune responses. LC are reduced in number in the epidermis adjacent to primary melanomas and increase in number in the lymphoid infiltrate that accumulates in the dermis deep to such tumours. The present study was undertaken to assess whether the reduction in epidermal LC was accompanied by alterations in their functional competence. We evaluated the capacity of LC from melanoma patients to augment lymphocyte responses to phytohaemagglutinin (PHA), tetanus toxoid and melanoma-associated antigens. Using a panning method to bind Fc receptor positive (FcR+) cells we separated LC-enriched (FcR+) and depleted (FcR-) fractions of epidermal cells. Lymphocyte responses to PHA and tetanus toxoid were increased in the presence of LC-enriched cell populations, but not in the presence of LC-depleted epidermal cells. In preliminary experiments LC-enriched cell populations did not help initiate detectable in vitro lymphoproliferative responses to autologous metastatic melanoma cell lines, allogeneic HLA-DR+ metastatic melanoma cell lines, or a 180-190 kD melanoma tumour-associated antigen. Future studies will investigate the capacity of LC to augment responses to melanoma-associated antigens on autologous primary melanomas.