The immune deficiency is the inability to develop an adequate immune response to the presence of antigens strangers, but not be disposed of properly.
These immunodeficiencies are inherited, so you are born with them.
Normally, they are caused by defects in B lymphocytes, which cannot produce enough antibodies. They can also be due to failures in the synthesis of the proteins that make up the complement or to malfunction of T lymphocytes.
If the problem is not being able to produce antibodies, the abnormalities appear after six months of life, when most of the IgG from the mother have been lost during pregnancy or through the placenta.
If the problem is in nonspecific immunity or is related to T lymphocytes, immunodeficiency phenomena can appear from the moment of birth.
Children with congenital immunodeficiency syndrome are called "bubble children" because they must live in a sterile room and avoid contact with people, animals, or objects that carry germs. One solution is bone marrow transplantation, capable of forming immunocompetent cells.
The acquired immunodeficiencies are more frequent than congenital immunodeficiencies. They appear as a consequence of some factors such as leukemia, radiation exposure, long treatment with immunosuppressants, ... or by serious diseases that weaken the immune system.
One of the most serious immunodeficiencies is AIDS (acquired immunodeficiency syndrome), produced by HIV (human immunodeficiency virus), which attacks and destroys T helper lymphocytes (TH). The body is defenseless against antigens and tumor cells, so the affected person can have significant infections and develop some types of cancers.
An individual is said to be seropositive when he has antibodies in his blood against the HIV virus. The cells that HIV infects are mainly T4 or helper lymphocytes.
As we saw, HIV is a retrovirus, so it has RNA (not DNA) as its genetic material. Specifically, it has two equal strands of single-stranded RNA. Its capsid is icosahedral and has a lipoprotein envelope.