HIV (Human Immunodeficiency Virus) is reffered to an infectious agent that decreases immunity severely. The AIDS virus work by infecting and quickly destroying the helper T cell. AIDS (Acquired Immunodeficiency syndrome) is a syndrome of decreasing immune system. AIDS is included as sexual contagious disease.
Immunodeficiency is in heritable. The inherited immunodeficiency generally reflects the inheritance failure of genes from one generation to the following generation so that the produced macrophage is unable to digest and destroy invader organism, i.e. Severe Combined Immunodeficiency (SCID). The person with SCID has B and T lymphocyte deficiency and he has to live in completely sterile environment to prevent infection.
When autoimmune disease attacks, the immune system will attack its own organs or tissues as if they are foreign substances. Autoimmune often occurs in diabetes and rheumatic.