neutrophils, microglia, osteoclasts and thrombocytes. Furthermore, this receptor can be also found in nonhematopoietic tissues such as endothelial cells, epithelial cells, myocytes and astrocytes. Considering the CX3CR1 abundance in the body, it was also found to be expressed by some types of malignant cells. Function CX3CR1 receptor is part of G-protein chemokine receptor family with the metabotropic function. Its intracellular signalling cascades are responsible for modulating cell activity rather towards higher active state as in survival, migration and proliferation. In the recognition for immune cells during inflammation, function of CX3CL1-CX3CR1 axis in the bloodstream is mainly recruitment of immune cells by migration through chemotaxis and diapedesis. Of course as a part of inflammatory immune response against pathogens is this role considerated as protective. However, as most of immune cells and proteins, in inflammatory or autoimmune diseases, CX3CR1 signalling is associated with some disease's pathophysiology. Expression of this receptor appears to be associated with lymphocytes. CX3CR1 is also expressed by monocytes and plays a major role in the survival of monocytes. Communication in blood vessels through CX3CL1-CX3CR1 axis between endothelial cells and monocytes is responsible for formation of extracellular matrix and angiogenesis. It was shown, that CX3CR1 can influence monocytes already in bone marrow by means of retention and release. Moreover in bone marrow, CX3CR1 influences bone remodeling through role in differentiation of osteoclasts and osteoblasts. CX3CL1/CX3CR1 axis role in the nervous system is to mediate communication between microglia, neuroglia and neurons for regulation of microglia activity, hence this axis plays neurodegenerative and neuroprotective function based on the physiological state. Fractalkine signaling has also recently been discovered to play a developmental role in the migration of microglia in the central nervous system to their synaptic targets, where phagocytosis and synaptic refinement occur. CX3CR1 knockout mice had more synapses on hippocampal neurons than wild-type mice. Structure CX3CR1 is integral membrane protein formed by 355 amino acids with molecular weight around 40 kDa, which consist of three distinguishable segments: extracellular, transmembrane and intracellular part. As a member of the biggest class of GPCR family the rhodopsin-like receptors, the intracellular part of receptor, C-terminus of the polypeptide and three intracellular loops, is a bounding place with conserved DRYLAIV motif for the heterotrimeric G protein. This family is also known as T-transmembrane receptors (7-TM) by reason of 7 α-helices of transmembrane protein, which are alternately located in the cell's cytoplasmic membrane. Extracellular side of CX3CR1