CD5L, also known as CD5 antigen-like, is secreted protein which mainly expressed by macrophages in lymphoid and inflammed tissues and regulates mechanisms in inflammatory responses, such as infection or atherosclerosis. It is able to inhibit lipid droplet size in adipocytes. CD5L acts as a key regulator of metabolic switch in T-helper Th17 cells. It is Participates in obesity-associated autoimmunity via its association with IgM, interfering with the binding of IgM to Fcalpha/mu receptor and enhancing the development of long-lived plasma cells that produce high-affinity IgG autoantibodies. It also acts as an inhibitor of apoptosis in macrophages: promotes macrophage survival from the apoptotic effects of oxidized lipids in case of atherosclerosis. It is involved in early response to microbial infection against various pathogens by acting as a pattern recognition receptor and by promoting autophagy.
CD5L, also known as CD5 antigen-like, is a soluble protein belonging to group B of the scavenger receptor cysteine-rich (SRCR) superfamily and contains three SRCR domains. It is a secreted glycoprotein and expressed by macrophages presentin lymphoid tissues (spleen, lymph node, thymus, and bone marrow). It binds to myelomonocytic and lymphoid cells and may play an important role in the regulation of the innate and adaptive immune systems. CD5L functions as a pattern recognition molecule by binding both lipoteichoic acid (LTA) on Gram positive and lipopolysaccharide (LPS) on Gram negative bacteria. and the SRCR domain 1 of CD5L retains both the LPS and LTA binding activities. In addtion, it is revealed that CD5L seems to play a role as an inhibitor of apoptosis.
The cluster of differentiation (CD) system is commonly used as cell markers in immunophynotyping. Different kinds of cells in the immune system can be identified through the surface CD molecules which associating with the immune function of the cell. There are more than 320 CD unique clusters and subclusters have been identified. Some of the CD molecules serve as receptors or ligands important to the cell through initiating a signal cascade which then alter the behavior of the cell. Some CD proteins do not take part in cell signal process but have other functions such as cell adhesion. CD5 is a member of the CD system. CD5 was found to be widely distributed in T-cells and B1 cells which is a subset of IgM-secreting B cells. CD5 also was found expressed in small lymphocytic lymphoma, hairy cell leukaemia and mantle cell lymphoma cells. CD5 serves to weaken the activating stimulus from the BCR so that the B1 cells can only reflect to the very strong stimuli but not the normal tissue proteins.
CD5 is a transmembrane glycoprotein of the conserved scavenger receptor cysteine-rich (SRCR) superfamily and expressed on thymocytes, peripheral T cells and a subset of B cells (B1-a). Moreover, CD5 also was found expressed in small lymphocytic lymphoma, hairy cell leukaemia and mantle cell lymphoma cells. The long cytoplasmic tail of CD5 has no intrinsic enzymatic activity, but contains four tyrosine phosphorylation sites, including an immunoreceptor tyrosine-based (ITAM)-like motif (pseudo-ITAM) and an immunoreceptor tyrosine-based inhibitory (ITIM)-like motif (pseudo-ITIM), as well as multiple potential serine and threonine phosphorylation sites. It physically associates with the T cell antigen receptor (TCR) and B cell antigen receptor (BCR), where it negatively modulates the activation and differentiation signals transduced by these receptors. CD5 also plays an important role in protection from activation-induced cell death and in the recognition of pathogen associated molecular patterns (PAMPS) present on fungal surfaces.
L-selectin (SELL), also known as CD62L, is a key adhesion molecule that regulates both the migration of leukocytes at sites of inflammation and the recirculation of lymphocytes between blood and lymphoid tissues. It belongs to the selectin family of proteins, and consisting of a large, highly glycosylated, extracellular domain, a single spanning transmembrane domain and a small cytoplasmic tail. L-selectin is the only selectin expressed on leukocytes and mediates a number of leukocyte-endothelial interactions. L-selectin acts as a ",homing receptor", for leukocytes to enter secondary lymphoid tissues via high endothelial venules. Ligands present on endothelial cells will bind to leukocyte expressing L-selectin, slowing leukocyte trafficking through the blood, and facilitating entry into a secondary lymphoid organ at that point. L-selectin-mediated lymphocyte recirculation is required for maintaining the appropriate tissue distribution of lymphocyte subpopulations including naï,ve and effector subsets such as regulatory T cells. In addition, L-selectin-mediated entry into peripheral lymph nodes is required for optimal induction of lymphocyte homeostatic proliferation during lymphopenia. Importantly, L-selectin has been shown to have both adhesive and signaling functions during leukocyte migration. L-selectin has also been shown to mediate leukocyte recruitment during chronic inflammatory and autoimmune diseases and thus is a potential therapeutic target for drug development.
High affinity immunoglobulin gamma Fc receptor I, also known as FCGR1 and CD64, is an integral membraneglycoprotein and a member of the immunoglobulin superfamily. CD64 is a high affinity receptor for the Fc region of IgG gamma and functions in both innate and adaptive immune responses. Receptors that recognize the Fc portion of IgG function in the regulation of immune response and are divided into three classes designated CD64, CD32, and CD16. CD64 is structurally composed of asignal peptidethat allows its transport to the surface of a cell, threeextracellularimmunoglobulin domainsof the C2-type that it uses to bind antibody, a hydrophobictransmembrane domain, and a short cytoplasmic tail. CD64 isconstitutivelyfound on only macrophages and monocytes, but treatment of polymorphonuclear leukocyteswith cytokines likeIFNγandG-CSFcan induce CD64 expression on these cells. The inactivation of the mouse CD64 resulted in a wide range of defects in antibody Fc-dependent functions. Mouse CD64 is an early participant in Fc-dependent cell activation and in the development of immune responses.
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