CD4 is a glycoprotien expressed on the surface of Helper T Cell
The Human Immunodeficiency Virus (HIV) seems to only infect the CD4 (or T-helper) cells of the immune system. The CD4 cells are responsible for activating and directing other immune system cells. HIV also infects macrophages and microglial cells that express the CD4 molecule on their surface. The virus can also infect a subtype of myeloid dendritic cells MDC-1.
Helper T cells, also known as CD4+ T cells, play a crucial role in activating killer T cells and B cells. Helper T cells recognize antigens presented by antigen-presenting cells, which triggers them to release signals that stimulate the activation and proliferation of killer T cells and B cells to mount an immune response against the specific pathogen.
Major histocompatibility complex (MHC) molecules display antigens on the surface of cells. There are two main classes: MHC class I, which presents antigens to CD8+ cytotoxic T cells, and MHC class II, which presents antigens to CD4+ helper T cells. These molecules play a crucial role in the immune response by enabling the recognition of foreign substances by T cells.
HIV is a retrovirus that primarily targets and infects CD4+ T cells, which are a type of white blood cell that plays a crucial role in the immune system.
CD4+ T lymphocytes, also known as T helper cells, are severely depressed in AIDS patients. These cells play a key role in coordinating the immune response against infections. Decreased CD4+ T cell levels result in immune suppression, making patients more susceptible to opportunistic infections.
The glycoprotein CD4 is a co-receptor. A co-receptor is "a cell surface receptor, which, when bound to its respective ligand, modulates antigen receptor binding or affects cellular activation after antigen-receptor interactions." (MediLexicon)
CD4 is a surface receptor expressed by helper T lymphocytes, known as CD4+ T cells. Its purpose is to stablize the interaction between the T cell receptor (on the T cell) and an antigen-bearing MHC Class II molecule (on an antigen presenting cell). Under the right circumstances, this interaction activates CD4+ T cells that recognize an invading pathogen. Activated CD4+ T cells do many things, and are required for a robust adaptive immune response.
CD4 T cells are activated in the immune response when they recognize antigens presented by antigen-presenting cells, such as dendritic cells. This recognition triggers the CD4 T cells to proliferate and differentiate into effector T cells, which help coordinate and regulate the immune response.
T cells (both CD4 "helper" and CD8 "cytotoxic" cells) are activated by antigen presenting cells (i.e. dendritic cells). This involves 3 different signals from the dendritic cell:1. Major Histocompatibility Complex (MHC) presents an antigen (foreign peptide) to the T cell2. A co-stimulatory signal (checking that it is a "professional" antigen presenting cell) which is a B7 molecule binding to a CD28 on the T cell3. Cytokines (signalling molecule)It is this 3rd type of signal, the cytokines which is important in the creation of the different T cells (CD8, or cytotoxic T cells and CD4, helper T cells).Dendritic cells are able to release different cytokines, which cause T cell differentiation.CD4 cells are presented antigen by MHC class II, whereas CD8 cells are presented antigen by MHC I.
The Human Immunodeficiency Virus (HIV) seems to only infect the CD4 (or T-helper) cells of the immune system. The CD4 cells are responsible for activating and directing other immune system cells. HIV also infects macrophages and microglial cells that express the CD4 molecule on their surface. The virus can also infect a subtype of myeloid dendritic cells MDC-1.
The CD4 count is the result of the most important test used to monitor HIV. The 'absolute' count is the same as the CD4 count. This is the result you get back from your doctor. The term 'absolute' is used to differentiate it from CD4 percentage (CD4%) which can also be used for clinical management.
helper T cells
CD4 T cells are a type of white blood or immune cell. Elevated levels suggest an immune response is underway. Most likely this is due to a mild infection but could also indicate autoimmunity (immune reaction against yourself).
1-Endogenous antigens(En.A) originate by the multiplication of pathogen inside the antigen presenting cell, such as pathogen is intracellular multiply in cytoplasm. 2-En.A presented via M.H.C1 molecule recognized by the CD8 and T-lymphocytes. 3-It includes viral and tumor antigens. 1-Exogenous antigens (Ex.A) originates outside and taken by antigen presenting cells when extracellular pathogen are engulfed and kill inside the phagolysosome. 2-Ex.A presented via M.H.C2 molecule recognized by CD4 and T-Lymphocytes. 3-It includes allergens,bacteria structures (like capsule, flagella e.t.c).
Helper T cells, also known as CD4+ T cells, play a crucial role in activating killer T cells and B cells. Helper T cells recognize antigens presented by antigen-presenting cells, which triggers them to release signals that stimulate the activation and proliferation of killer T cells and B cells to mount an immune response against the specific pathogen.
Major histocompatibility complex (MHC) molecules display antigens on the surface of cells. There are two main classes: MHC class I, which presents antigens to CD8+ cytotoxic T cells, and MHC class II, which presents antigens to CD4+ helper T cells. These molecules play a crucial role in the immune response by enabling the recognition of foreign substances by T cells.
HIV, the virus that leads to the disease of AIDS, infects cells in our immune system called T-Helper Cells. These cells have a protein on the surface called CD4, so T-Helper cells are also CD4+ cells. The main purpose of the CD4+ cell is to bind to protein pieces (epitopes) of bacteria and other pathogens that are presented to them by antigen-presenting cells (APCs). APCs includedendritic cells (DCs) and macrophages. When a CD4+ cell recognizes a pathogen, it releases lymphokines, which attract other immune cells to the area, enhancing the immune response (and ultimately causing inflammation). CD4+ cells also recognize antigens shown to them by B-Cells and release chemicals that cause the B-cells to form antibodies specific to that pathogen or invader. Once the antibodies are released, they bind to the pathogen, which allows phagocytes to bind to the invader and eventually kill it. Therefore, CD4+ cells are essential for a well-informed immune system and a healthy body. AIDS develops when enough HIV has infected and led to the death of CD4+ cells that less than 200 CD4+ cells per microliter of blood remain (healthy individuals have approximately 1000-1200 CD4+ cells per microliter). Without a good supply of CD4+ cells, an AIDS patient's immune system lacks the most effective method for recognizing pathogens/invaders that could easily be recognized and destroyed by a healthy person's immune system. Therefore, they develop diseases that healthy people never have to worry about.