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.
A CD4 test measures the number of CD4 cells, a type of white blood cell that plays a crucial role in the immune system, particularly in fighting infections. It is commonly used to monitor the immune status of individuals with HIV, as HIV primarily targets and destroys CD4 cells. Lower CD4 counts indicate a weakened immune system and a higher risk of opportunistic infections. Regular monitoring of CD4 levels helps guide treatment decisions for HIV patients.
CD4 and CD8 proteins are co-receptors on T cells that play crucial roles in T cell activation. CD4 is primarily found on helper T cells and binds to MHC class II molecules on antigen-presenting cells, enhancing the interaction and signaling necessary for T cell activation. In contrast, CD8 is found on cytotoxic T cells and binds to MHC class I molecules, facilitating recognition and response to infected or abnormal cells. Both co-receptors help stabilize the interaction between the T cell and the antigen-presenting cell, leading to effective immune responses.
CD4+ T cells, also known as helper T cells, are a type of white blood cell that plays a crucial role in the immune system. They help coordinate the immune response by signaling other immune cells, such as B cells and cytotoxic T cells, to respond to infections. CD4+ T cells are characterized by the presence of the CD4 glycoprotein on their surface and are essential for recognizing antigens presented by other cells. Their decline is notably associated with the progression of HIV infection and the development of AIDS.
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.
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.
CD4 receptors are primarily found on a subset of T cells known as CD4+ T helper cells. These cells play a crucial role in the immune response by assisting other immune cells, such as B cells and cytotoxic T cells. CD4 receptors are also present on some macrophages and dendritic cells, but their primary association is with CD4+ T lymphocytes.
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
A CD4 test measures the number of CD4 cells, a type of white blood cell that plays a crucial role in the immune system, particularly in fighting infections. It is commonly used to monitor the immune status of individuals with HIV, as HIV primarily targets and destroys CD4 cells. Lower CD4 counts indicate a weakened immune system and a higher risk of opportunistic infections. Regular monitoring of CD4 levels helps guide treatment decisions for HIV patients.
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).
CD4 and CD8 proteins are co-receptors on T cells that play crucial roles in T cell activation. CD4 is primarily found on helper T cells and binds to MHC class II molecules on antigen-presenting cells, enhancing the interaction and signaling necessary for T cell activation. In contrast, CD8 is found on cytotoxic T cells and binds to MHC class I molecules, facilitating recognition and response to infected or abnormal cells. Both co-receptors help stabilize the interaction between the T cell and the antigen-presenting cell, leading to effective immune responses.
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).