Allojenik refers to a type of organism or cell that is genetically different from the host organism. This term is often used in the context of transplantation, where tissues or organs from one individual are transplanted into another individual of the same species but with different genetic makeup. In biology, allojenic responses can trigger immune reactions, as the recipient's immune system may recognize the transplanted cells as foreign. This is a critical consideration in procedures like organ transplantation, where compatibility between donor and recipient is essential to prevent rejection.