The immune system recognises a transplanted kidney as foreign body and mounts immune response through cellular and humoral mechanisms leading to acute or chronic rejection, which ultimately results in graft loss. Over the last five decades, there have been significant advances in the understanding of the immune responses to transplanted organs in both experimental and clinical transplant settings. Modulation of the immune response by using immunosuppressive agents has led to successful outcomes after kidney transplantation. The paper provides an overview of the general organisation and function of human immune system, immune response to kidney transplantation, and the current practice of immunosuppressive therapy in kidney transplantation in the United Kingdom.