Recent views on tumour antigens and their relation to host defence mechanisms.

Abstract

Summary: Recent views on tumour antigens and their relation to host defence mechanisms.P. Hersey, Aust. N.Z. J. Med., 1977, 7, pp. 526–536. Tumour antigens on some human tumours can be detected by antibody produced against the tumour by the host. Tumour antigens defined in this way appear to be multiple and show diversity between different individuals. Several different categories of tumour antigens have been defined in animal studies which appear to be likely candidates for an equivalent role on haman tumour cells. These include altered histocompatibility antigens, oncogenic viral antigens and antigens similar to those on foetal tissue. The evidence for their expression on human tumours is reviewed. Problems in definition of these antigens as specific for tumours arise because of their expression on normal tissue under certain circumstances. It is suggested that previous exposure of human subjects to a number of these antigens on normal tissue produces a state of pre-sensitization to many of these antigens in both normal and tumour bearing subjects. This pre-existing state of sensitization has presented problems in the development of tumour specific assays of immune reactivity to monitor disease activity in human tumour bearing subjects. This problem appeared particularly marked in relation to assays of cell mediated immunity where it is thought that cytotoxicity to naturally occurring antigens may often obscure the “disease related” immune response. Information regarding the biological importance of the various tumour antigens in tumour rejection is reviewed. Preliminary evidence suggests that the role of the different tumour antigens in tumour rejection may vary. The factors which may determine the role of tumour antigens in immune rejection are poorly understood but may include the rate of shedding of antigens from the cell surface, the concentration of cell surface antigens and the number of pre-existing lymphoid cells which can recognise the tumour antigen. Although there are considerable deficiencies in our understanding of tumour antigens on human tumours, existing information appears to provide promising avenues for the development of diagnostic and immunotherapeutic procedures which will aid in the management of tumour bearing patients.