chemokine

Chemokines are a group of molecules that affect the behaviour of white blood cells. Most chemokines are involved in attracting white blood cells. Different chemokines attract different types of white blood cell.

Soluble chemical messengers that attract white blood cells to the site of infection. There are two structural categories of chemokines: alpha (CXC) and beta (CC).

Also called beta chemokines. Studies of the relationship between HIV and these immune system chemicals have shown the complex exchanges that take place when HIV and white blood cells meet. Chemokines are intracellular messenger molecules secreted by CD8+ cells whose major function is to attract immune cells to sites of infection. Recent research has shown that HIV-1 needs access to chemokine receptors on the cell surface to infect the cell. Several chemokines -- called RANTES, MIP-1A, and MIP-1B -- interfere with HIV replication by occupying these receptors. Findings suggest that one mechanism these molecules use to suppress HIV infectivity is to block the process of fusion used by the virus to enter cells.

Chemokines: A cytokine that produces chemotaxis.

Chemotaxis: The chemical attraction of neutrophils and macrophages (and T cells, when cell-mediated immunity has been activated) to a pathogen.

soluble molecules that chemically attract lymphocytes and other cells

CHEMOKINE: a soluble factor secreted by certain immune system cells that stimulates the activity of other cells. Chemokines have chemoattractant properties and act as messengers between cells. Alpha chemokines contain an amino acid between 2 cysteine residues; beta chemokines do not contain an intervening amino acid. Certain chemokines (e.g., MIP-1-alpha, MIP-1-beta, RANTES) have been shown to affect the activity of HIV; certain chemokine receptors (e.g., CCR-5, CXCR-4) are necessary for entry by HIV into cells.

These are a subfamily of cytokines classified by their low molecular weight and ability to bind heparin. Over 30 chemokines and 10 receptors have been described. They are very important in leukocyte recruitment and may also play a role in activation. There are 2 main families of chemokines classified on the position of conserved cysteine residues:

Alpha chemokines (or CXC): eg IL-8, this family predominately chemoattracts neutrophils

Beta chemokines (or CC): eg MCP-1, this family predominately chemoattracts monocytes and lymphocytes

Nb. Some chemokine receptors are used by HIV to gain entrance into CD4+ T cells.

chemokine - a subset of the cytokines, with specific functions related to chemoattraction of immune cells (chemotaxis). There are several families of these immune proteins, including the C-C chemokines and the beta-chemokines, which are produced by activated immune cells. We are only now beginning to identify and understand the function of most of many chemokines.

Some chemokines and their cell surface receptors that have been shown to act as co-receptors in HIV infection:

RANTES - Receptor Activated Neutrophil T-cell Expression and Secretion

MIP-1a/MIP-1ß - Macrophage Inflammatory Protein-1(alpha/beta)

MCP-1 - Macrophage Chemotactic Protein-1

CKR-5 (also CCR-5)- ChemoKine Receptor 5, a receptor for beta chemokines that lies on the surface of monocytes and macrophages that HIV uses to enter and infect these cells.

CXCR-4 - CXC (chemokine) Receptor 4 (also known as fusin, LESTR, HUMSTR); a chemokine receptor on the surface of CD4+ T-cells that HIV uses to enter and infect these cells.

Cytokines - are proteins (usually GlycoProteins) of relatively low molecular mass and often consisting of just a single chain. They are chemicals secreted by various Lymphocytes to activate other cells, which regulate all the important biological processes: Cell Growth, Cell Activation, Inflammation, Immunity, Tissue Repair, Fibrosis and Morphogenesis. - Some Cytokines (ie: IL-8) are also Chemotactic for specific cell types, and are now called *Chemokines*. Although Cytokins are considered to be a Family, this is a Functional rather than a Structural concept; these Proteins are not all chemically related. (ex: Interferons and InterLeukins). # 30