S100B is a Ca2+-binding protein mainly concentrated in astrocytes. Its levels in biological fluids (cerebrospinal fluid, peripheral and cord blood, urine, saliva, amniotic fluid) are recognized as a reliable biomarker of active neural distress. Mounting evidence now points to S100B as a Damage Associated Molecular Pattern molecule which, when released at high concentration, through its Receptor for Advanced Glycation Endproducts, triggers tissue reaction to damage in a series of different neural disorders.

Sclerostin is a human bone tissue protein encoded by the SOST gene Sclerostin belongs to the bone morphogenetic protein (BMP) family of antagonists, and is involved in the anti-anabolic processes of bone formation.

This protein plays a key role in maintaining the balance between the processes of bone formation and resorption (bone remodeling).

The N-propeptide of collagen IIA (PIIANP) is a product of a specific splice form of type II collagen that is synthesized by chondroprogenitor cells. PIIANP is synthesized by chondrocytes.

Soluble form of the interleukin-2 receptor (sIL-2R) is secreted upon T-cell activation. Increased blood levels of sIL-2R occur in a variety of immunological diseases. sIL-2R serum measurements are commonly conducted in clinical practice as it may help to facilitate diagnosis of specific immune-mediated diseases.

The adipokine leptin realizes signal transduction via four different leptin receptor (OB-R) isoforms. The amount of functionally active OB-R, however, is affected by constitutive shedding of the extracellular domain. The product of the cleavage process, the so-called soluble leptin receptor (sOB-R), is the main binding protein for leptin in human blood and modulates its bioavailability.

RANK is the receptor for the pro-osteoclastogenesis cytokine RANKL (also known as TNFRSF11 or TRANCE), which is expressed on the surface of the osteoblast cells and binding of RANKL to the RANK is required for the commitment and differentiation of the preosteoclast. The binding of RANKL to its receptor activates NF-kappaB.

The soluble urokinase plasminogen activator receptor (suPAR) is the bioactive form of uPAR, a membrane-bound glycoprotein, and it is primarily expressed on the surface of immunologically active cells. Mirroring local inflammation and immune activation, suPAR has gained interest in many diseases.

Surfactant proteins (SP)-A and -D are pattern recognition molecules of the collectin family of C-type lectins. SP-A and SP-D are part of the innate immune system and regulate the functions of other innate immune cells, such as macrophages.

Syndecans are transmembrane proteoglycans with heparan and chondroitin sulfate chains attached to their extracellular domain. Syndecans play a major role in inflammation, mainly by regulating leukocyte extravasation and cytokine function. At the same time, syndecans can undergo cytokine mediated changes in their expression levels during inflammation.

Acid phosphatase is a ubiquitous lysosomal enzyme. Bone acid phosphatase is resistant to l(+)-tartrate. Tartrate-resistant acid phosphatase (TRAP) is a group of enzymes synthesized mainly in bone spleen and lungs. Other acid phosphatases are present in many other tissues (e.g., prostate, erythrocytes, macrophages, and platelets). The fraction of TRAP that is most specific of the osteoclasts is the subform b of the isoenzyme 5 (TRACP5b).