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Proliferating cell nuclear antigen (PCNA), a protein of 30 kDa molecular weight also known as cyclin, forms a trimer ring around a DNA double-helix. It binds to a variety of other nuclear proteins and thereby organises biochemical processes at the DNA replication fork. PCNA thereby assumes important functions in DNA synthesis, repair and processing, the regulation of cell cycle and even apoptosis.
Anti-PCNA antibodies occur in systemic lupus, where they represent a rare specificity (< 10 % of SLE patients). However, their presence alone or in combination with other autoantibodies should alert the clinician to the presence of defined or evolving SLE.

Celiac disease is an enteropathy that is characterized by intestinal lesions of variable severity. Tissue-type transglutaminase (tTG) is believed to be the predominant autoantigen for celiac disease and the corresponding autoantibodies show higher sensitivity and specificity than anti-gliadin antibodies. Highly pure recombinant human tTG is now available to replace the traditionally used tTG fraction from guinea pig.
Tissue-type transglutaminase antigens have been specifically modified for improved handling: exchange of an active site amino acid eliminates the protein cross-linking activity of the enzyme, while maintaining the native three-dimensional structure and the enzyme's secondary GTPase activity. This engineering assures reproducible properties of the antigen preparations through the absence of variable and ill-defined covalent aggregates of tTG antigen and host cell proteins.

Matrix metalloproteinases are a family of zinc and calcium-dependent endopeptidases that break down extracellular matrix proteins. The MMP9 is secreted as a 92kDa zymogen. Cleavage of ProMMP-9 results in the active enzyme, having a molecular weight of approximately 82kDa. MMP9 is composed of the following domains: a gelatin-binding domain consisting of three fibronectin type II units, a catalytic domain containing the zinc-binding site, a proline-rich type V collagen-homologous domain and a hemopexin-like domain. MMP9 is produced by the several cell types: monocytes, macrophages, neutrophils, keratinocytes, fibroblasts, osteoclasts and endothelial cells. MMP9 is involved in inflammatory responses, tissue remodeling, wound healing, tumor growth and metastasis. MMP9 may also play an important part in local proteolysis of the extracellular matrix and in leukocyte migration, as well as in bone osteoclastic resorption. MMP9 cleaves type IV and type V collagens into large C-terminal three quarter fragments and shorter N-terminal one quarter fragments. MMP9 can also degrade fibronectin but not laminin or Pz-peptide.
MMP9 defects may be a cause of susceptibility to intervertebral disc disease (IDD), also known as lumbar disk herniation (LDH).

Chitinase 3-Like 2 (CHI3L2) is similar to bacterial chitinases but lacks chitinase activity. CHI3L2 protein is secreted and is involved in cartilage biogenesis. CHI3L2 is a lectin, which binds chitooligosaccharides and other glycans with high affinity, but not heparin.

Fatty acid binding protein 9 (FABP9) belongs to the fatty acid-binding proteins (FABPs) which are a family of small, extremely conserved, cytoplasmic proteins to bind long-chain fatty acids and other hydrophobic ligands. FABP9 is found in midpachytene spermatocytes and round spermatids, and comprises part of the perinuclear theca. FABP9 probably links intracellular membranes and signals abnormal sperm formation during spermatogenesis.

Tryptase alpha/beta-1 (TPSAB1) is a tryptase which is the key neutral protease present in mast cells and is discharged upon the coupled activation-degranulation response of this cell type. TPSAB1 is enzymatically active only as a heparin-stabilized tetramer, and is resistant to all known endogenous proteinase inhibitors. TPSAB1 is implicated as a mediator in the pathogenesis of asthma and other allergic and inflammatory disorders.

MMP9 is part of the matrix metalloproteinase family. MMP enzymes take part in the dismantle of extracellular matrix in different physiological pathways, for instance wound healing, bone development, reproduction etc. the enzyme is also involved in pathological pathways: metastasis, arthritis and intracerebral hemorrhage.

Major Histocompatibility Complex Class II DR Beta 1 also known as HLA-DRB1 ia a member of the HLA class II beta chain paralogs. Molecule class II is a heterodimer consisting of an alpha (DRA) and a beta chain (DRB), both anchored in the membrane. HLA-DRB1 takes an essential part in the immune system by presenting peptides derived from extracellular proteins. Class II molecules are expressed in antigen presenting cells (APC: B lymphocytes, dendritic cells, macrophages). Furthermore, the beta chain is approximately 26- 28 kDa. It is encoded by 6 exons. While exon one encodes the leader peptide; exons 2 and 3 encode the two extracellular domains; exon 4 encodes the transmembrane domain; and exon 5 encodes the cytoplasmic tail.

The cytokine IL-1 alpha or hematopoietin 1 is a member to the interleukin 1 family, encoded by the IL1A gene in humans. Essentially Il-1 is in charge of inflammation and the rising of fever and sepsis. In order to disturb the mentioned processes and treatment for diseases, inhibitors for Interleukin 1 alpha are being developed. Neutrophils and macrophages are the main activators of IL-1 alpha, as well as endothelial and epithelial cells. By binding to the il1 receptor it is a major part in the immune response regulation. In the activation process of tumor necrosis factor-alpha the IL1A has a part as well, and has physiological, metabolic and hematopoietic activities.

C-type Lectin Domain Family 1 Member B, also known as CLEC1B. NK-Natural killer cells express multiple calcium-dependent (C-type) lectin-like receptors, for instance CD94 (KLRD1; MIM 602894) and NKG2D (KLRC4; MIM 602893), which interact with major histocompatibility complex class I molecules and either inhibit or else activate cytotoxicity and cytokine secretion. CLEC1B is a C-type lectin-like receptor which is expressed in myeloid cells as well as in NK cells.

Human Factor IX also called Christmas-Factor is a glycoprotein, which is synthesized in the liver and belongs to the serine proteases system and is part of the S1 peptidase family.
Lack of Factor-IX causes Hemophilia-B meaning Christmas Disease. Factor-IX has a N-terminus region which contains 12xGla residues which asist the calcium dpendant binding of Factor-IX to the phospholipid surface. Factor-IX is activated by either factor XIa or the factor VIIa/tissue factor/phospholipid complex. Cleavage yields the intermediate IXa, which is subsequently converted to the fully active form IXab.
Factor-IX binds initially to exosites on the factor XIa heavy chain, followed by interaction at the active site with subsequent bond cleavage. Coagulation factor IX is activated by interaction with the erythrocyte membrane, causing intrinsic coagulation. Chaperones & lectins act simultaniously to guarantee the proper folding of Factor-IX and the retention of mutant molecules. Human Factor IX, activated by either the Contact or Tissue Factor Pathway, is responsible for the activation of Factor X to Xa.

Matrix metalloproteinases are a family of zinc and calcium-dependent endopeptidases that break down extracellular matrix proteins. The MMP9 is secreted as a 92kDa zymogen. Cleavage of ProMMP-9 results in the active enzyme, having a molecular weight of approximately 82kDa. MMP9 is composed of the following domains: a gelatin-binding domain consisting of three fibronectin type II units, a catalytic domain containing the zinc-binding site, a proline-rich type V collagen-homologous domain and a hemopexin-like domain. MMP9 is produced by the several cell types: monocytes, macrophages, neutrophils, keratinocytes, fibroblasts, osteoclasts and endothelial cells. MMP9 is involved in inflammatory responses, tissue remodeling, wound healing, tumor growth and metastasis. MMP9 may also play an important part in local proteolysis of the extracellular matrix and in leukocyte migration, as well as in bone osteoclastic resorption. MMP9 cleaves type IV and type V collagens into large C-terminal three quarter fragments and shorter N-terminal one quarter fragments. MMP9 can also degrade fibronectin but not laminin or Pz-peptide.
MMP9 defects may be a cause of susceptibility to intervertebral disc disease (IDD), also known as lumbar disk herniation (LDH).

Cystatins are a superfamily of cysteine proteinase inhibitors found in both plants and animals. They comprise a group of proteinase inhibitors, widely distributed in tissues and body fluids, and form tight complexes with cysteine proteases such as cathepsin B, H, L and S. Cystatin C, a secreted molecule of this family, is of interest from biochemical, medicine and evolutionary points of view. Cystatin C, with molecular weight of 13260 Da, is composed of 120 amino acids, lacks carbohydrate and has two disulfide bridges located near the carboxyl terminus. Cystatin C is increased in patients with malignant diseases, and is related to the insufficiency of renal function and appears to be a better marker than creatinine. On the other hand, low levels of cystatin C involve cause the breakdown of the elastic laminae and, subsequently, the atherosclerosis and abdominal aortic aneurysm.

Energy Homeostasis Associated (ENHO) participates in glucose homeostasis maintenance and lipid metabolism. ENHO is expressed in the liver and the brain. The role of ENHO in obesity or diabetes is studied.

Pregnancy Specific Beta-1-Glycoprotein 1 (PSG1) is a member of a subgroup of transcription factors which are phosphorylated upon binding to promoter sequences. PSGs belong to the carcinoembryonic antigen (CEA) family and function as early biochemical markers of syncytiotrophoblast formation. Furthermore, PSG1 is assumed to mediate placental vascular morphogenesis by enhancing VEGF-A production and endothelial tube formation. PSG1 is a major product of the syncytiotrophoblast, reaching concentrations of 100- 290 mg/l at term in the serum of pregnant women.

REG protein was shown to be stimulated during the regeneration of pancreatic islets. Since then, many Reg-related proteins have been identified in humans and other animals. In human, the four REG family genes, i.e., REG 1 alpha, REG 1 beta, REG-related sequence (RS) and HIP/PAP, have so far been isolated. These Reg-related proteins are classified into four subfamilies according to their amino-acid sequences, but they share a similar structure and physiological function. Reg protein is a growth factor for pancreatic beta cells and also suggests that the administration of Reg protein could be used as another therapeutic approach for diabetes mellitus. Human REG cDNA which encodes a 166-amino acid protein with a 22-amino acid signal peptide. The amino acid sequence of human REG protein has 68% homology to that of rat Reg protein.

GMCSF is a cytokine that controls the production, differentiation, and function of granulocytes and macrophages. The active form of the protein is found extracellularly as a homodimer. This gene has been localized to a cluster of related genes at chromosome region 5q31, which is known to be associated with interstitial deletions in the 5q- syndrome and acute myelogenous leukemia. Other genes in the cluster include those encoding interleukins 4, 5, and 13.
GM-CSF stimulates the growth and differentiation of hematopoietic precursor cells from various lineages, including granulocytes, macrophages, eosinophils and erythrocytes.

NUDT9 is a member of a superfamily of Nudix hydrolases. NUDT9 functions as a highly specific adenosine diphosphate ribose pyrophosphatase which hydrolyzes ADP ribose to AMP and ribose 5'-phosphate. In addition, NUDT9 may be involved in the regulation of the menstrual cycle and may be related to the proliferation of glandular cells in the human endometrium.

Acid phosphatase, prostate (ACPP) is a non-specific tyrosine phosphatase, which dephosphorylates a varied number of substrates under acidic conditions (pH 4-6) including alkyl, aryl, and acyl orthophosphate monoesters and phosphorylated proteins. ACPP has lipid phosphatase activity and inactivates lysophosphatidic acid in seminal plasma.

The enzyme Arylsulfatase A, also known as cerebroside-sulfatase, is responsible to break down sulfatides. The main molecule that Arylsulfatase A breaks down is cerebroside 3-sulfate into cerebroside and sulfate. The enzyme is encoded by the ARSA gene in humans. Phosphate can form a covalent bond with the Arylsulfatase A’s active site 3-oxoalanine, thus, inhibits the protein.

TDP1 belongs to the phospholipase D family and contains two PLD phosphodiesterase domains. TDP1 is involved in repairing stalled topoisomerase I-DNA complexes by catalyzing the hydrolysis of the phosphodiester bond between the tyrosine residue of topoisomerase I and the 3-prime phosphate of DNA. TDP1 may also remove glycolate from single-stranded DNA containing 3-prime phosphoglycolate, suggesting a role in repair of free-radical mediated DNA double-strand breaks. Mutations in the TDP1 gene are linked to the disease spinocerebellar ataxia with axonal neuropathy (SCAN1).

Chromogranin-A Isoform 1 Preproprotein or CHGA is part of the neuroendocrine secretory proteins of the chromogranin/secretogranin family. CHGA is a precursor of numerus enzymes such as pancreastatin, catestatin, vasostatin-1,vasostatin-2, and parastatin. The protein acts as a negative regulator the neuroendocrine activity of autocrine or nearby cells (paracrine). CHGA causes further production of secretory granules that contains insulin in pancreatic islet beta cells.

SUMF1 is a part of the SUMF protein family. SUMF1 catalyzes the hydrolysis of sulfate esters by oxidizing a cysteine residue in the substrate sulfatase to an active site 3-oxoalanine residue called C-alpha-formylglycine. Mutations in this gene will cause multiple sulfatase deficiency meaning a lysosomal storage disorder.

Hemopexin (or haemopexin) is a plasma protein that binds heme with the highest affinity of any known protein. Hemopexin is generally expressed in liver, and belongs to acute phase reactants, the synthesis of which is induced after inflammation. Heme is potentially very toxic because of its ability to intercalate into lipid membrane and to generate hydroxyl radicals. Hemopexin’s function of scavenging the heme released or lost by the turnover of heme proteins such as hemoglobin defends the body from the oxidative damage that free heme can cause. Additionally, hemopexin discharges its bound ligand for internalisation upon interacting with a specific receptor located on the surface of liver cells. This hemopexin function is in order to preserve the body's iron. Hemopexin’s levels in the serum are an indication of how much heme is present in the blood. Low Hemopexin levels show that there is a lot of it in the serum. For that reason, low hemopexin levels indicate that there has been consid