Type IV or Delayed-Type Hypersensitivity (DTH)

Type IV or Delayed-Type Hypersensitivity (DTH)

Type IV hypersensitivity is also called Delayed-Type Hypersensitivity (DTH). It is a cell mediated hypersensitivity reaction. It is due to T lymphocytes. It is not due to antibody. It is called delayed type because the reaction appears late. Usually it appears after 48 to 72 hours. Sometimes more time also needed. This delay is due … Read more

Major Histocompatibility Complex I – Definition, Structure, Mechanism, Functions

Major Histocompatibility Complex I - Definition, Structure, Mechanism, Functions

Major Histocompatibility Complex class I (MHC I) is a cell surface glycoprotein which is found on almost all nucleated cells and platelets. In human it is known as Human Leukocyte Antigen (HLA). The main classical forms are HLA-A, HLA-B and HLA-C. MHC I is heterodimer in structure. It is made up of one heavy alpha … Read more

Type III Hypersensitivity – Definition, Types, Mechanism, Examples

Type III Hypersensitivity - Definition, Types, Mechanism, Examples

Type III hypersensitivity is also called immune complex mediated reaction. It is caused by deposition of antigen-antibody complex in tissue. The antibodies involved are mainly IgG and IgM. In this reaction soluble antigen is present in blood. This antigen combines with antibody. So immune complex are formed.The reaction is as follows- Soluble antigen + IgG/IgM … Read more

Type II (Cytotoxic) Hypersensitivity – Definition, Mechanism, Examples

Type II (Cytotoxic) Hypersensitivity - Definition, Mechanism, Examples

Type II (Cytotoxic) Hypersensitivity is an antibody mediated hypersensitivity reaction in which IgG or IgM antibodies react with antigen present on the surface of body cell or extracellular matrix. In this reaction, the antibody binds with the normal host cell antigen. Then the immune system identifies this cell as harmful cell. It causes injury of … Read more

Type 1 (Anaphylactic) Hypersensitivity Reaction – Definition, Mechanism, Examples

Type 1 (Anaphylactic) Hypersensitivity Reaction - Definition, Mechanism, Examples

Type I hypersensitivity reaction is an immediate hypersensitivity reaction. It is also called anaphylactic hypersensitivity. It is produced against some harmless foreign substances called allergens. The allergens may be pollen, food, drugs, dust and insect venom. These substances enter into the body and the immune system reacts against them. The reaction is very fast and … Read more

Autoimmunity – Definition, Types, Tolerance, Pathogenesis, Mechanisms

Autoimmunity - Definition, Types, Tolerance, Pathogenesis, Mechanisms

Autoimmunity is an abnormal condition in which the body immune system react against its own healthy cells and tissues. It means the immune system cannot properly identify self-antigen and foreign antigen. So, the body’s own tissues are attacked like they are infectious agents. Normally, the immune system has a protective mechanism called self-tolerance. This tolerance … Read more

Immune Response – Definition, Factors, Types, Examples

Immune Response - Definition, Factors, Types, Examples

Immune response is a protective response of body against harmful foreign agents. It is done by physical barriers, immune cells and chemical signals. It helps to maintain normal health of body. The main function of immune response is to identify and destroy pathogens, foreign toxins and abnormal cells. It also removes damaged cells from body. … Read more

Antigen Processing, and Presentation – MHC Class I, Class II,

Mechanism of Antigen Processing and Presentation

Antigen processing and presentation is a biological mechanism by which the immune system detect the foreign antigen and abnormal cell. It is important for activation of T lymphocytes. It helps in formation of specific adaptive immune response against pathogen. In this process, the foreign antigen such as viral protein, bacterial protein or abnormal cellular protein … Read more

MHC Molecule – Properties, Types, Structure

MHC Molecules (Major Histocompatibility Complex) - Definition, Properties, Class, Types, Pathways

Major Histocompatibility Complex (MHC) molecules are glycoproteins present on the surface of cells. These are encoded by a large group of genes. In human, these genes are present on chromosome 6 and are called Human Leukocyte Antigens (HLA). The main function of MHC molecules is to bind short peptide fragments and present them on the … Read more