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Image of CD4 co-receptor binding to MHC (Major Histocompatibility Complex) non-polymorphic region. In molecular biology, CD4 (cluster of differentiation 4) is a glycoprotein that serves as a co-receptor for the T-cell receptor (TCR). CD4 is found on the surface of immune cells such as helper T cells, monocytes, macrophages, and dendritic cells.
CD4 immunoadhesin was first developed in the mid-1990s as a potential therapeutic agent and treatment for HIV/AIDS. The protein is a fusion of the extracellular domain of the CD4 receptor and the Fc domain of human immunoglobulin G (IgG), the most abundant antibody isotype in the human body. [1]
CR3 is a human cell surface receptor, found on polymorphonuclear leukocytes (mostly neutrophils), NK cells, and mononuclear phagocytes like macrophages, which is capable of recognizing and binding to many molecules found on the surfaces of invading bacteria. Binding to the receptor causes phagocytosis and destruction of the foreign cell. CD11c
Antigen presentation: MHC molecules bind to both T cell receptor and CD4/CD8 co-receptors on T lymphocytes, and the antigen epitope held in the peptide-binding groove of the MHC molecule interacts with the variable Ig-Like domain of the TCR to trigger T-cell activation [26]
Since CD4 receptor binding is the most obvious step in HIV infection, gp120 was among the first targets of HIV vaccine research. Efforts to develop HIV vaccines targeting gp120, however, have been hampered by the chemical and structural properties of gp120, which make it difficult for antibodies to bind to it. gp120 can also easily be shed from the surface of the virus and captured by T cells ...
As well as being involved in forming a complex with MHC-II with TCR to control T-cell fate, the CD4 receptor is infamously the primary receptor that HIV envelope glycoprotein GP120 binds to. [6] In comparison, CD28 acts as a ‘co-coreceptor’ (costimulatory receptor) for the MHC-II binding with TCR and CD4. CD28 increases the IL-2 secretion ...
Interaction of TCR and co-receptors CD4 and CD8 with MHC molecules. During positive selection, co-receptors CD4 and CD8 initiate a signaling cascade following MHC binding. [19] This involves the recruitment of Lck, a tyrosine kinase essential for T cell maturation that is associated with the cytoplasmic tail of the CD4 or CD8 co-receptors.
Exposed on the surface of the viral envelope, the glycoprotein gp120 binds to the CD4 receptor on any target cell that has such a receptor, particularly the helper T-cell. Strains of HIV-1 have been isolated that are able to enter host cells that are CD4 negative. This CD4-independence is associated with spontaneous mutation in the env gene.