So tissue typing is the process that involves determining the major histocompatibility complex antigens of the host individual and finding a donor that is most compatible that contains the least mismatches. Another important type of method that is used to basically solve these complications and is probably used virtually on all cases of grafting an organ transplant is immunosuppression. Now, immunosuppression deals with using different types of chemical agents that are extracted from other organisms or synthesized in a lab. And what these chemical agents do is they essentially decrease the ability of our immune system to actually fight off different infections including these grafts and organs that are transplanted into our bodies. So these chemical agents interfere with the processes of forming white blood cells. For example, they can interfere with the process of protein synthesis or DNA replication and that will greatly hinder the ability of our immune system to actually form any type of white blood cell.