consists of N-terminus of the polypeptide chain and three extracellular loops, forming a binding place for its main ligand CX3CL1, but also CCL26 (Eotaxin-3): has lower binding affinity when compared to fractalkine), immunoglobulins or infectious agents. Signalling cascade CX3CL1-CX3CR1 axis' signalling commences via activation of the receptor by its agonist's binding. It is followed by conformational change and component's dissociation of the heterotrimeric G complex, which consists of three subunits: α (alpha), β (beta) and γ (gamma). Several important signalling pathways are triggered by separated parts of G protein (Gα and Gβγ) such as the PLC/PKC pathway, the PI3K/AKT/NFκB pathway, the Ras/Raf/MEK/ERK (MAPK) pathway (or p38 and JNK) and the CREB pathway. All of those signalling cascades are responsible for diverse cellular behaviours and regulations, in terms of increased proliferation, survival and cell growth, metabolic regulation, induction of migration, apoptosis resistance and secretion of hormones and inflammatory cytokines. Products of CX3CR1 signalling cascades possess importance in the immune response of CX3CR1 positive hematopoietic cells. Clinical significance CX3CR1 and immune cells are strongly connected due to its abundant cell surface expression. Therefore, clinical meaning of CX3CR1 can be found in diseases connected with immunity. CX3CR1 is able to increase accumulation of immune cells in the affected body part, which results in disease aggravation. Few examples: allergies, Rheumatoid arthritis, Renal diseases, Chronic liver disease or Crohn's disease. CX3CR1 is also a coreceptor for HIV-1, and some variations in this gene lead to increased susceptibility to HIV-1 infection and rapid progression to AIDS. Since CX3CR1 plays a major role for interaction between endothelial cells and immune cells, it can aid vascular build up on the artery walls (plaque), thus it has been associated with Atherosclerosis. In addition, this may lead to thrombosis, other cardiovascular diseases or even cerebral ischemia. CX3CL1-CX3CR1 axis has an ability to control neurological inflammation through activation of microglia. Its role in brain pathologies can be therefore protective but also detrimental. There are connections between microglia and neurodegenerative disorders like Alzheimer's disease, Parkinson's disease or even with neurocognitive HIV-dementia. Moreover, CX3CR1 variants have been described to modify the survival time and the progression rate of patients with amyotrophic lateral sclerosis. Mutations in CX3CR1 are associated to dysplasia of the hip. Homozygous CX3CR1-M280 mutation impairs human monocyte survival and deteriorates outcome of human systemic candiasis. As mentioned before, this receptor and its ligand are important for the metabolism of the bone