Immune response to human keratoacanthoma.

Immune reactivity to human keratoacanthoma was investigated by microcytotoxicity tests and immunofluorescence. IgM and complement were consistently present in lesions; IgG and fibrin were infrequent. No evidence of in vivo bound immunoglobulin was found on the surface of keratoacanthoma cells by membrane immunofluorescence. Neither patients' sera nor peripheral blood leukocytes showed significant cytotoxicity against autochthonous tumour cells in microtitre assays. This study fails to support the view that regression of human keratoacanthoma is mediated by immunological mechanisms.