Chemokines are small heparin-binding proteins that direct
the movement of circulating leucocytes to the site of
inflammation and injury.
Chemokines are 8-10 kD proteins with 20-70 % homology
in amino acid sequence.
Chemokines act like chemoattractant cytokine.
Proteins are classified into the chemokine family based on their
structural characteristics, not just their ability to attract cells.
They possess conserved amino acids that are important for creating their 3-
dimensional or tertiary structure, such as (in most cases) four cysteines that
interact with each other.
Most chemokines have 4 cysteine residues which form disulphide bonds:
1. CC class –
The first two cysteines are adjacent (example: MCP-1, RANTES)
2. CXC class-
The first two cysteines are not adjacent (example: IL-8)
3. C class –
Only has 2 cysteines not 4 (example: Lymphotactin)
4. CX3C class –
Has 3 amino acids between the first two cysteines and a different N-
Chemokine receptors are defined by function, not structure:- they
bind chemokines and transduce signal.
To date all known chemokine receptors are members of the 7TM
GPCR superfamily, coupling to Gi.
The two N-terminal cysteines of CXC chemokines (or α- chemokines) are
separated by one amino acid, represented in this name with an "X”.
Glutamic acid leucine Glutamic acid leucine
arginine positive arginine negative
(ELR- Motif) (ELR without Motif)
Eg. IL-8 Eg. IL-8, GCP2,
ELR +ve :
means that induce the migration of neutrophils and interact with
CXCR1 and CXCR2 chemokine receptors.
eg. IL-8 which induces neutrophils to leave the bloodstream and enter
into the surrounding tissue.
ELR –ve :
means that induce migration of lymphocytes and interact with CXCR1 to
CXCR7 chemokine receptors.
eg. IL-8, GCP2, GRO-α,β,Ƴ, MCP1-5 $ RANTES,
MCP( monocyte chemoattractant proteins)
RANTES (regulated upon activation , normal T-cell expressed and
Having ability to induce migration of monocytes, NK
cells, dendritic cells.
Eg. MCP- Monocyte chemoattractant protein (MCP)-1 (CCL2)
specifically attracts monocytes and memory T cells.
Other example is RANTES-
c-c motif ligand 5 (i.e. CCL5) is a protein which in humans is
encoded by the CCL5 gene known as RANTES.
That attracts cells such as T-cells, basophils, & eosinophils, that
express the receptor CCR5.
in which 3 amino acid residue is present between two cysteines
Its also known as α chemokines
It work as both-
C chemokines (or γ chemokines)
Unlike all other chemokines in that it has only two cysteines; one
N-terminal cysteine and one cysteine downstream.
Two chemokines have been described for this subgroup and are
1. XCL1 (lymphotactin-α) and
2. XCL2 (lymphotactin-β).
GDP+ G-protein subunit G-protein become inactive
binding of the chemokine ligand, chemokine receptors associate
with G-proteins then GDP GTP and the dissociation of the
different G protein subunits. The subunit called Gβ activates
an enzyme known as PLC
Now, PLC cleaves PIP2 to form two second messenger molecules
called IP3 and DAG
DAG activates another enzyme called PKC, and IP3 triggers the
release of calcium from intracellular stores.
Eg. IL8 binds to receptors CXCR1 &CXCR2, a rise of calcium
they activate PLD and that initiate intracellular signalling cascade
called MAP kinase pathway
2. Asthma and allergy
6. Inflammatory diseases such as
- rheumatoid arthritis
- psoriasis and
- inflammatory bowel disease
Schematic representation of the proposed mechanism of lymphocyte
recruitment by CXCR3-binding chemokines in endocrine autoimmunity.
Thyroid follicular cells secrete CXCL9, CXCL10, and CXCL11 upon
stimulation with IFN-γ and TNF-α. Chemokines, in turn, drive chemotaxis
from blood vessels of T cells expressing the chemokine receptor CXCR3.
This particular subset of T cells shows a prevalent Th1 immune phenotype
and produces IFN-γ, thus perpetuating the inflammatory process.
This loop of events supports the active role played by thyroid follicular cells
and in general by cells of the glandular epithelium (a similar mechanism has
been demonstrated for β-cells and adrenal cells of the zona fasciculata) in
determining the specificity of the infiltrating lymphocytes and in maintaining
the autoimmune process.
Chronic rejection of allografts is mediated by a tandem of
alloantigen-dependent and -independent factors. The oxidative
stress inherent to the transplantation procedure operates within a
milieu of immunologic factors that contribute to the later
development of chronic rejection.
The aim of this study is investigate the role that early myocardial
oxidative stress signaling pathways may have in the
development of GCAD using rodent heart transplant models.
Our working hypothesis is that myocardial oxidative stress
following cardiac transplantation contributes to the development
of GCAD via a bcl-2-associated mechanism.
Intramolecular disulfide bonds typically join the first to
third, and the second to fourth cysteine residues, numbered as
they appear in the protein sequence of the chemokine.
The first two cysteines, in a chemokine, are situated close
together near the N-terminal end of the mature protein, with the
third cysteine residing in the centre of the molecule and the
fourth close to the C-terminal end.
A loop of approximately ten amino acids follows the first two
cysteines and is known as the N-loop.
This is followed by a single-turn helix, called three β-
strands and a C-terminal α-helix. These helices and strands are
connected by turns called 30s, 40s and50s loops; the third and
fourth cysteines are located in the 30s and 50s loops.