|Immunodeficiency means when the body's immune response is reduced or absent. As the immune system protects the body from harmful substances called antigens like microorganisms, cancer cells, blood or tissues from another person and toxins, it is mediated by the immune response that includes responses by white blood cells which is composed of neutrophils and lymphocytes. Neutrophils engulf the foreign particle and destroy them by a process called phagocytosis. Lymphocytes can be divided into two types: T lymphocytes and B lymphocytes. T lymphocytes directly attack antigens (cellular immunity). B lymphocytes produce antibodies (humoral immunity) that attach to the antigen or foreign particle and make phagocytes and body chemicals, such as complement proteins, that helps in the destruction of the antigen or foreign particle.
In immunodeficiency there is the failure of one or more parts of the immune system. It can be divided into two categories primary immunodeficiency and acquired immunodeficiency. Primary immunodeficiency is caused by congenital/inherited defects and in primary immunodeficiency there is either deficiency in B cells, T cells or both B and T cells or due to defective phagocytes. Whereas acquired immunodeficiency is caused by a disease that affects the immune system. There are certain tests that can diagnose immunodeficiency disorder. The tests that indicate immunodeficiency disorder are low white blood cell count, low antibody or immunoglobulin levels, low complement levels. Immunodeficiency can be treated by gene therapy or bone marrow transplantation as no drug can be helpful in this disorder.