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Complement C4c is a degradation product of C4b which is cleaved by C4b/C3b inactivator to yield C4d and C4c.
Complement C4c interacts with C1 and C2 to form C3 convertase of the classic activation pathway. Systemic lupus erythematosus (SLE) is often associated with congenital C4 deficiency. Reduced levels of components of the classic pathway (C1, C2, C4, C3) are common after such activation, e.g. in SLE, acute serum sickness and conditions associated with circulating immune complexes.

The C3c component is central in both complement activation pathways, with different specific proteolytic systems cleaving it to form C3 convertase. Cleavage of C3 releases C3a and the C3b fragment which is part of the alternative C3 convertase. C3 levels can be low because of decreased synthesis or due to consumption. High C3 levels are seen in highly acute or chronic inflammation, hepatic cholestasis and during the third trimester of pregnancy.
Unwanted complement activation is a major cause of tissue damage in various pathological conditions and contributes to quite a few immune complex diseases.
Compstatin is an effective inhibitor of the activation of complement component C3 and thus blocks a central and essential step in the complement cascade. The specific binding site on C3, the configuration in the bound form, and the exact mode of action of compstatin are unknown. The crystal structure of compstatin in complex with C3c reveals that the compstatin-binding site is formed by the macroglobulin (MG) domains 4 and 5. This binding site is part of the structurally stable MG-ring created by domains MG1–6 and is distant from any other known binding site on C3. Compstatin does not modify the conformation of C3c, while compstatin itself undergoes a large conformational alteration upon binding.

C1q is the first component of the classical pathway of complement activation. C1q along with the enzymatically active components C1r and C1s forms the C1 complex. When C1 binds to immunoglobulins in the form of immune complexes, it leads to activation of C1r and C1s proteases and a further activates the classical pathway of complement. C1q is a glycoprotein that belongs to the collectin family, having a molecular weight of about 410-462 kDa. C1q is a hexamer composed of globular heads attached to collagen-like triple-helix tails. The globular heads of C1q exclusively bind to the CH2 domain of IgG molecules or the CH3 domain of IgM. Each heavy chain of the immunoglobulin molecule contains a single binding site for C1q. Given that C1q must bind to no less than two heavy chains in order to alter its conformation and activate C1r and C1s, its activation follows only after binding to immunoglobulins in the form of immune complexes bound to multivalent antigens. C1q’s main physiological role is in the clearance of immune complexes and apoptotic bodies from the organism. Interruption of this process may lead to development of autoimmunity. Individuals with genetic deficiencies of C1q or other components of the classical pathway are at risk to develop SLE. C1q specifically binds to apoptotic bodies of human keratinocytes, vascular endothelial cells and lymphocytes. Complement components C1q and bound C3 mediate the clearance of apoptotic bodies. Hence, C1q may advance the clearance of autoantigens, avoiding stimulation of the immune system. Nonetheless, an extended exposition of the immune system to the neoepitope exposed on C1q molecules bound to immune complexes or apoptotic bodies could ultimately lead to an autoimmune response against C1q itself and to an altered complement function. C1q deficiency may also lead to disruption of the negative selection of autoreactive B cells. C1q along with other specific recognition proteins bind to the highly conserved lupus antigens (dsDNA and nuclear proteins) and activate the complement system. Autoantibodies against C1q (anti-C1q) are found in a number of autoimmune and infectious diseases like glomerulonephritis (GN) and lupus erythematosus (SLE), these antibodies are significant in clinical practice due to their negative predictive value.

C3d is derived from human C3 after a series of proteolytic cleavages.C3d is prepared from purified human C3. The C3 is converted to C3b by treatment with the natural human C3 convertase and this C3b is converted to iC3b. Finally, this iC3b is cleaved with trypsin to yield C3d.If the C3b precursor was attached to a surface (as occurs during complement activation) the iC3b, C3dg and C3d fragments would remain covalently attached to that surface.C3d is able to attach to a surfaceonly during complement activation on a surface. Surface-bound C3d is linked to the target through an ester or an amide covalent bond. Ester bonds are unstable, thusC3d releasesfrom the particle.

Albumin is synthesized in the liver as preproalbumin which has an N-terminal peptide that is removed before the nascent protein is released from the rough endoplasmic reticulum. The product, proalbumin, is in turn cleaved in the Golgi vesicles to produce the secreted albumin. Albumin is a soluble, monomeric protein which comprises about one-half of the blood serum protein. Albumin functions primarily as a carrier protein for steroids, fatty acids, and thyroid hormones and plays a role in stabilizing extracellular fluid volume. Mutations in this gene on chromosome 4 result in various anomalous proteins. Albumin is a globular unglycosylated serum protein of molecular weight 65,000. The human albumin gene is 16,961 nucleotides long from the putative 'cap' site to the first poly (A) addition site. It is split into 15 exons which are symmetrically placed within the 3 domains that are thought to have arisen by triplication of a single primordial domain.
HSA is widely used to stabilize blood volume generally from donors but the fear of contamination such as HIV & Hepatitis has enticed great interest in the recombinant form which is identical to the natural blood.

IL10 is a cytokine produced primarily by monocytes and to a lesser extent by lymphocytes. This cytokine has pleiotropic effects in immunoregulation and inflammation. It down-regulates the expression of Th1 cytokines, MHC class II Ags, and costimulatory molecules on macrophages. It also enhances B cell survival, proliferation, and antibody production. This cytokine can block NF-kappa B activity, and is involved in the regulation of the JAK-STAT signaling pathway. Knockout studies in mice suggested the function of this cytokine as an essential immunoregulator in the intestinal tract.

C3b is derived from native C3 upon cleavage with the alternative pathway C3 convertase and release of C3a.Native human C3b is a glycosylated polypeptide chain having2 disulfide-linked chains. C3b is essential to the function of all 3complement pathways.Initiation of each pathway generates proteolytic enzyme complexes (C3 convertases) which binds the target surface. These enzymes cleave a peptide bond in C3 releasing the anaphylatoxin C3a and activating C3b. Most of the C3b created during complement activation. Surface-bound C3b is needed in all 3 pathways for effective activation of C5 and formation of C5b-9 complexes which lyse the target cell membrane. Surface-bound C3b and its breakdown products iC3b and C3d are identifyid by various receptors on lymphoid and phagocytic cells which use the C3b ligand to stimulate antigen presentation to cells of the adaptive immune system. It results in an expansion of target-specific B-cell and T-cell populations.

Native human C8 is a glycosylated protein consist of 3 polypeptide chains: The alpha chain and the gamma chain are disulfide linkedwhereas, The beta chain is non-covalently bound to the a-g complex. C8 is necessary for formation of the membrane attack complex and is activated by binding on the cell membrane newly-formed C5b,C6,C7 complexes. Each pathway of complement activation generates proteolytic enzyme complexes which bind the target surface. These enzymes cleave a peptide bond in the larger alpha chain of C5 releasing C5a and activating C5b. Although C5b is unstable it remains bound to the activating complex for a few minutes during which it binds a single C6 from the surrounding fluid or it decays and is no longer capable of forming MAC.The C5b,6 complex may also remain connected to the C3/C5 convertase where the binding of a single C7 exposes a membrane-binding region and C5b,6,7 can enter into the bilipid layer of the target cell. Each C5b-7 complex can bind 1 molecule of C8 causing the complex to enter more firmly into the membrane.

Interleukin-1 ra is a member of the interleukin 1 cytokine family. This protein inhibits the activities of interleukin 1, alpha (IL1A) and interleukin 1, beta (IL1B), and modulates a variety of interleukin 1 related immune and inflammatory responses. This gene and five other closely related cytokine genes form a gene cluster spanning approximately 400 kb on chromosome 2. A polymorphism of this gene is reported to be associated with increased risk of osteoporotic fractures and gastric cancer. Four alternatively spliced transcript variants encoding distinct isoforms have been reported.

Alpha-2 Macroglobulin is a serine proteases inhibitor, which inhibits coagulation by inactivating thrombin and Kallikrein, it inhibits fibrinolysis by inactivating plasmin and involved in transport. Alpha-2-Macroglobulin is a large plasma protein, which is produced by the liver, it’s composed of 4 identical subunits bound together by -S-S- bonds. A2M is able to inactivate many kinds of proteinases (including serine-, cysteine-, aspartic- and metalloproteinases). A2M has a 35 amino acid "bait" region in its structure. Proteinases bind and cleave the “bait” region become bound to A2M. Macrophage receptors recognize the proteinase-A2M complex and clear it from the system. A2M binds to and removes MMP-2 and MMP-9 (active forms of the gelatinase) from the circulation using scavenger receptors on the phagocytes. The levels of Alpha-2-macroglobulin are increased in nephrotic syndrome which is a condition where the kidneys start to leak out some of the smaller blood proteins. Due to its large size, A2-macroglobulin is retained in the bloodstream. Increased production of all proteins causes A2-macroglobulin concentration to increase. Chronic renal failure might lead to amyloid by alpha-2-macroglobulin. A2M is raised in cirrhosis, pregnancy and diabetes.

Plasminogen activator inhibitor-1 is the principal inhibitor of tissue plasminogen activator(tPA) and uPA, the activators of plasminogenand hence fibrinolysis(the physiological breakdown of blood clots). It is a serine protease inhibitor(serpin) protein (SERPINE1). The other PAI, plasminogen activator inhibitor-2(PAI-2) is secreted by the placentaand only present in significant amounts during pregnancy. In addition, protease nexinacts as an inhibitor of tPA. SERPINE1, however, is the main inhibitor of the plasminogen activators.

FCGR3B, also known as CD16b belongs to the Ig super family. FCGR3B encodes a glycosylphosphatidylinositol (GPI)-anchored protein which is expressed constitutively by neutrophils. FCGR3B binds to complex or aggregated IgG and monomeric IgG. Different from III-A, FCGR3B cannot arbitrate antibody-dependent cytotoxicity and phagocytosis. FCGR3B operate to capture immune complexes in peripheral blood circulation that does not activate neutrophils.

Interleukin-1 receptor type 1 (IL1R1) associates with the co-receptor IL1RAP to form the high affinity interleukin-1 receptor complex, which mediates interleukin-1-dependent activation of NF-kappa-B, MAPK and other pathways. IL1R1 is a central mediator involved in numerous cytokine induced immune and inflammatory responses.

Type IV collagen is a major structural component of basement membranes. It is a multimeric protein composed of 3 alpha subunits, which are encoded by 6 different genes, alpha 1 through alpha 6. Each of these alpha subunits can form a triple helix structure with 2 other subunits to form type IV collagen. The Goodpasture syndrome is a condition in which autoantibodies bind to the collagen molecules in the basement membranes of alveoli and glomeruli. The epitopes that elicit these autoantibodies are restricted basically to the non-collagenous C-terminal domain of the protein. There are numerous alternative transcripts that appear to be unique to the human COL4A3 and alternative splicing is limited to the six exons that encode this C-terminal domain. COL4A3 is also linked to an autosomal recessive form of Alport syndrome. The mutations contributing to the Alport syndrome are also situated within the exons that encode this C-terminal region. COL4A3 is organized in a head-to-head conformation with another type IV collagen gene so that each gene pair shares a common promoter. Several exons of COL4A3 are interspersed with exons of an uncharacterized gene which is on the opposite strand.

TBE is caused by tick-borne encephalitis virus (TBEV), a member of the family Flaviviridae.
A closely related virus in Far Eastern Eurasia, Russian spring-summer encephalitis virus (RSSEV).
The family Flaviviridae includes other tick-borne viruses are closely related to TBEV and RSSEV, such as Omsk hemorrhagic fever virus & Kyasanur Forest virus.
Louping ill virus is also a member of this family.

Prealbumin is a thyroid hormone-binding protein that transports thyroxine from the bloodstream to the brain. Prealbumin is a carrier protein which transports thyroid hormones in the plasma and cerebrospinal fluid, and also transports retinol (vitamin A) in the plasma. Transthyretin consists of a tetramer of identical subunits and is dominantly produced in the liver. Mutations in Prealbumin are related to amyloid deposition, affecting predominantly peripheral nerve and/or the heart. The diseases caused by mutations include amyloidotic polyneuropathy, euthyroid hyperthyroxinaemia, amyloidotic vitreous opacities, cardiomyopathy, oculoleptomeningeal amyloidosis, meningocerebrovascular amyloidosis, and carpal tunnel syndrome. Prealbumin is an indicator of protein-energy malnutrition since it has a circulating half life of 2 days and reacts swiftly to changes in nutritional status.

GNLY is part of the SAPLIP family and is located in the cytotoxic granules of T cells, which are discharged upon antigen stimulation. GNLY is localized in cytotoxic granules of cytotoxic T lymphocytes and natural killer cells, and it has antimicrobial activity against M. tuberculosis and other organisms. GNLY is an antimicrobial protein that kills intracellular pathogens. GNLY is active against a wide range of microbes, including Gram-positive and Gram-negative bacteria, fungi, and parasites. Kills Mycobacterium tuberculosis.

Interleukin-3 is a pleiotropic cytokine produced primarily by activated T cells.
IL-3 is thought to function via specific cell surface receptors to stimulate the proliferation, differentiation and survival of haematopoietic cell lines. IL-3 has also been shown to affect the functional activity of a variety of other cell types including mast cells, eosinophils, megakaryocytes and basophils.

RARRES2 is a secreted chemotactic protein that initiates chemotaxis through the ChemR23 G protein-coupled seven-transmembrane domain ligand. RARRES2 is upregulated by the synthetic retinoid tazarotene and found in a vast variety of tissues. RARRES2 acts as an adipokine, and is truncated on both termini from the proprotein. RARRES2 is structurally related to the cathelicidin precursors, cystatin C and kininogens. RARRES2 promotes calcium mobilization and chemotaxis of immature dendritic cells and macrophages. RARRES2 is secreted as a precursor of little biological activity, which requires proteolytic cleavage of its COOH-terminal domain to be exchangeed into a potent and highly specific agonist of ChemR23. RARRES2 signals via its receptor, ChemR23 (CMKLR1), as a positive regulator of adipocyte differentiation and metabolic function. The Chemerin receptor acts as a coreceptor for SIV and some primary HIV-1 strains. The Chemerin receptor has another ligand, called tazarotene-induced gene.

C3 is central to the activation of all 3 pathways of complement activation. Initiation of each pathway generates proteolytic enzyme complexes which binds the target surface. These enzymes cleave a peptide bond in C3 releasing the anaphylatoxin C3a and activating C3b. Most of the C3 activated during complement activation never attaches to the surface due to its thioester reaction with water forming fluid phase C3b which is rapidly inactivated by factors H and I forming iC3b. Surface-bound C3b is necessary in all 3 pathways for efficient activation of C5 and formation of C5b-9 complexes that lyse the target cell membrane.

E-selectin which is also called Endothelial leukocyte adhesion molecule 1, ELAM1, ELAM belongs to a family of divalent cation-dependent carbohydrate-binding glycoproteins or adhesion molecules. Eselectin is expressed on the surface of endothelial cells and mediates the interaction of leukocytes and platelets with endothelial cells during an inflammatory response. E-selectin is present in single copy in the human genome and contains 14 exons spanning about 13 kb of DNA.

Borrelia belongs to a genus of bacteria of the spirochete phylum. Borrelia causes borreliosis, which is a zoonotic, vector-borne disease transmitted mainly by ticks and some by lice, depending on the species. Of the 36 known species of Borrelia, 12 are distinguished to cause Lyme disease or borreliosis and are transmitted by ticks. The main Borrelia species causing Lyme disease are Borrelia burgdorferi, Borrelia afzelii, and Borrelia garinii. The Borrelia genus members have a linear chromosome which is about 900 kbp in length as well as an excess of both linear and circular plasmids in the 5-220 kbp size range. The plasmids are atypical, as compared to most bacterial plasmids, since they contain many paralogous sequences, a large number of pseudogenes and, in some cases, essential genes. Moreover, a number of the plasmids have features suggesting that they are prophages.