THE HLA SYSTEM - AN INTRODUCTION

The cellular identity is determined by the cell surface antigens. The recognition of self and non-self in vertebrates is mainly controlled b y antigens and coded for by the major histocompatibility complex (MHC) . Upon recognition of a foreign antigen, the immune system does not on ly initiate a reaction with the help of cytotoxic T-cells, phagocytes and humoral antibodies; memory cells are also generated, enabling a ve ry swift and powerful response after repeated exposure to the same for eign antigens. These characteristics, although essential for the survi val of the organism in a hostile environment, can markedly limit the l ife of useful and potentially lifesaving organtransplants.