Polymorphism in the major histocompatibility complex (MHC.
HIV is different in structure from other retroviruses. It is roughly spherical with a diameter of about 120 nm, around 60 times smaller than a red blood cell. It is composed of two copies of positive-sense single-stranded RNA that codes for the virus's nine genes enclosed by a conical capsid composed of 2,000 copies of the viral protein p24.The single-stranded RNA is tightly bound to.
The immune system distinguishes two groups of foreign substances. One group consists of antigens that are freely circulating in the body. These include molecules, viruses, and foreign cells. A second group consists of self cells that display aberrant MHC proteins. Aberrant MHC proteins can originate from antigens that have been engulfed and broken down (exogenous antigens) or from virus.
Major Histocompatibility Complex Class I Protein Molecule The MHC has three main proteins (class I, II and III) as mentioned earlier. A general feature of these proteins is their immunoglobulin-like formation. The MHC class I protein is an ? chain made up of three domains namely ?1, ?2, ?3. The ?1 sits on a unit of the non-MHC molecule referred to as ?2 micro-globulin (Haig, 1997). On the.
Immunoglobulin class switching, also known as isotype switching, isotypic commutation or class-switch recombination (CSR), is a biological mechanism that changes a B cell's production of immunoglobulin from one type to another, such as from the isotype IgM to the isotype IgG.During this process, the constant-region portion of the antibody heavy chain is changed, but the variable region of the.
There are two major types of MHC gene families: MHC class I and MHC class II. MHC class I genes are expressed on the cell membrane of all nucleated cells and defend against intracellular threats (as viral pathogens) and malignant cells. MHC class II genes are mainly expressed on specialized antigen-presenting cells of the immune system, which monitor the extracellular environment and use MHC.
An inflammatory response begins when a pathogen stimulates an increase in blood flow to the infected area. Blood vessels in that area expand, and white blood cells leak from the vessels to invade the infected tissue. These white blood cells, called phagocytes engulf and destroy bacteria. The area often becomes red, swollen, and painful during an inflammatory response.
These fragments are then presented to the T cell via a specific peptide-binding groove of the MHC class II molecule. T cells will only respond if they recognise the class II molecule and the specific antigen fragment being presented. By contrast, superantigens bind simultaneously as unprocessed intact proteins directly to the MHC class II molecule and to the T-cell receptor (TCR).