The concept of immunodeficiency

Immunodeficiency is a due to the human body's immune system developmental defects or immune response disorders cause human anti-infective ability is low, the clinical manifestations of recurrent infection or severe infectious diseases.

Types of immunodeficiency

Immune deficiency is divided into primary and secondary categories. The former is mainly seen in infants and children. Such as children born after repeated infections, it should go to the hospital to check the immune function, to determine whether the immune deficiency. Children with immunodeficiency can not receive a variety of live vaccines, otherwise it may have serious consequences.

Cause of immunodeficiency

The body has a variety of internal stimuli or the ability to respond to the invasion, immunity is a protective response of the body.

The role of immunity is to identify and eliminate alien substances in order to achieve the maintenance of the body's physiological balance and stability of the state. The results of immunological reactions in the normal circumstances of the body benefit, but under certain conditions, but also can be harmful. The main function of immunity is to remove pathogens or antigenic substances, is the performance of anti-infection process; removal of aging in vivo, degeneration of cells and some of the waste material composition, is to maintain the stability of the balance of the body's environment; immune surveillance, the elimination of degeneration cells , More common to eliminate cancer cells.

If in another case, due to excessive immune function or reduced, can cause adverse effects on the body without a variety of reactions, and cause damage to the body. Excessive immune function seen in hyperthyroidism, can cause allergic diseases as the representative of autoimmune diseases; and immunodeficiency is due to decreased immune function and showed the response, resulting in body infections and malignant tumors. Immune deficiency can be divided into two categories, one is congenital; the other is acquired, and the pathogenesis of AIDS is the main Secretary for cell immunity, immune function of TH lymphocytes, which showed reduced immune function, resulting in Clinical series of opportunistic infections and malignant tumors, so AIDS is acquired acquired disease, known as acquired immunodeficiency syndrome.

Immunodeficiency disease can be divided into congenital hereditary immunodeficiency disease and acquired immunodeficiency disease secondary to the two categories, they will lead to immune dysfunction or deletion, prone to serious infection or tumor.

【Congenital defects】

Congenital immunodeficiency defects cause different parts of the degree of immune dysfunction caused by different. According to the immune cells and components involved in different, can be divided into specific immune defects and non-specific immune deficiency.

【Specific defects】

1. B cell defective disease

 50% to 70% of congenital immunodeficiency disease. Defects occur in the B lymphocyte progenitor stage, B lymphocytes can not mature, so they can not generate antibodies. So the disease is characterized by the reduction or deletion of immunoglobulin levels, the immunoglobulin defects can be a variety of immunoglobulin reduction, can also be a class or subclass of immunoglobulin reduction. Hypogammaglobulinaemia (Bruton syndrome), selective IgA, IgM and IgG subclass defects are all such cases.

2. T cell defective disease

5% to 10% of congenital immunodeficiency disease. Mainly due to congenital thymic hypoplasia caused by the reduction in the number of T cells can also be due to certain enzymes or membrane glycoprotein and other molecules caused by lack of T cell dysfunction. Digeorge syndrome (congenital thymic dysplasia) is the representative of such diseases.

3. T and B cell combined defective disease

The cause and severity of the combined immunodeficiency disease is uncertain. If the defect occurs in the lymphatic stem cell stage, resulting in severe loss of T lymphocytes and B lymphocytes, severe combined immunodeficiency disease will occur, the patient showed a variety of microorganisms susceptible to infection.

【Non-specific defects】

1. Phagocytosis

Phagocytic cells include phagocytes, monocytes and neutrophils in the blood. Congenital phagocytic cell defects mainly refers to the dysfunction caused by phagocytic diseases, the relative incidence of 1% to 2%, the most common chronic granulomatous disease.

2. complement system defects

The disease is due to complement components of the body components or its regulatory proteins due to genetic defects.

【Acquired defects】

Secondary immunodeficiency disease refers to the occurrence of other diseases (such as chronic infection), radiation, long-term use of immunosuppressive agents and nutritional disorders caused by the immune system transient or lasting damage, resulting in immune dysfunction. Secondary immunodeficiency disease can be cellular immunodeficiency, or humoral immune deficiency, or both. According to the different causes of the secondary immunodeficiency can be divided into two categories. secondary to certain diseases, immunodeficiency and iatrogenic immune deficiency.

Infection：

Many viruses, bacteria, fungi and protozoa infections can often cause the body immune function is low. Such as measles virus, rubella virus, cytomegalovirus, severe Mycobacterium tuberculosis or leprosy infection can cause patients with T cell function decline. Especially HIV-induced AIDS is most serious.

Malignant neoplasms：

Malignant tumors, especially lymphoid tissue, can often progressively suppress the immune function of patients. In the widely metastatic cancer often appear in the cellular immune and humoral immune function is low.

Protein loss：

Suffering from chronic glomerulitis, nephrotic syndrome, acute and chronic gastrointestinal diseases and large area burns or scalds, protein, including a large number of loss of immunoglobulin; suffering from chronic wasting disease, increased protein consumption; gastrointestinal malabsorption and malnutrition , Protein synthesis, the above-mentioned various causes of immunoglobulin can reduce the humoral immune function weakened.

【Iatrogenic defects】

(1) long-term use of immunosuppressive agents, cytotoxic drugs and certain antibiotics

Large doses of adrenal cortical hormone can lead to complete suppression of immune function. Antitumor drugs (folic acid antagonists and alkylating agents) can inhibit T and B cell differentiation and maturation, thereby inhibiting immune function. Certain antibiotics, such as chloramphenicol, inhibit the production of antibodies and the proliferative responses of T cells and B cells to mitogens.

(2) radiation damage

Radiation therapy is a malignant tumor and inhibit the rejection of the same organ and organ transplantation is an effective means. While most lymphocytes are very sensitive to gamma rays. Large doses of radiation damage can cause permanent immunodeficiency.