Inherited combined immunodeficiency affects both T lymphocytes and B lymphocytes. It is often fatal within the first year of life because there is no resistance to disease or infection. This is a desired part of treatment for disorders such as autoimmune disorders . It is used after organ transplantation to prevent transplant rejection . Malnutrition , particularly with lack of protein , can cause acquired immunodeficiency.
Many cancers can cause immunodeficiency.
Increasing age also reduces the effectiveness of the immune system. There is also reduced lymphocyte number and activity with increasing age. Safe sex practices and avoiding the sharing of body fluids may help to prevent HIV infection and AIDS . Good nutrition may prevent acquired immunodeficiency caused by malnutrition . Suppression of the immune system may be desired in the treatment of certain disorders, or it may be a side effect of some treatments.