Chemokines

The defining feature of chemokines is their function as che-
motactic molecules – that is, they attract cells along a gradi-
ent of low to high chemical concentration. Chemokines are
involved in the trafficking of cells of the immune system –
particularly from the blood into the tissues and tissues into
lymphatics – and also have the ability to activate immune
cells. Like cytokines, chemokines are pleiotropic. All chemo-
kines have a similar structure relating to the configuration of
cysteine residues that gives rise to four families:

■  Two cysteines separated by any other amino acid
residue (X) is CXC.

■  Two cysteines next to each other is CC.

■  One cysteine is C.

■  Two cysteines separated by any three amino acids are
CX3C.

Receptors on the surface are denoted by ‘R’, and are all
distinctive G-coupled protein receptors with seven trans-
membrane spanning domains. Some chemokines are
released by many nucleated cells in response to inflamma-
tion and have a role in chemotaxis, attracting immune cells
to inflammatory foci (e.g. CXCL8 (interleukin 8)); others are
released in a programmed fashion by specialized cells in the
immune system and have specific functions. CXCL12, for
example, is necessary for the development of  secondary
lymphoid organs.

Anti-inflammatory drugs that block chemokine functions,
or drugs that promote cell activation and migration, for
example into tumours, are being developed in wide variety.