A common tumour specific antigen. I. Restriction in vivo to malignant neoplastic tissue.

(1) The antigenic activity of basic protein extracts of a variety of human tissues towards sensitized lymphocytes from cancer patients has been studied using the macrophage electrophoretic migration method.(2) Basic protein prepared from human tumour tissue has antigenic properties which differ from basic protein prepared from normal tissues, from hyperplastic tissue and even tumour bearing host tissue.(3) Tumour type antigenic molecules are at least 10(4) times less numerous on normal cells than on tumour cells. If our reasoning is accepted then they are absent from normal cells, and thus restricted in vivo to malignant cells.(4) Hyperplastic tissues (gynaecomastia, etc.) do not contain cancer basic protein.(5) Human chronic lymphatic leukaemic leucocytes possess the same type of cancer antigenic activity as solid tumours. This antigenic activity is not shared by normal lymphocytes.