S-100b from bovine brain is a calcium-binding protein predominantly expressed in astrocytes and select neuronal populations. Structurally, it forms a homodimer (beta-beta) and plays crucial roles in neurodevelopment, including the differentiation and maturation of astrocytes and oligodendrocytes, as well as promoting neurite outgrowth and protecting neurons from apoptosis at physiological (low) concentrations. S-100b is also involved in maintaining blood–brain barrier integrity and modulating synaptic plasticity and memory formation.

Pathologically, elevated S-100b levels are associated with a range of neurological diseases, including Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, multiple sclerosis, epilepsy, traumatic brain injury, and cerebrovascular disorders. At high concentrations, S-100b acts as a proinflammatory cytokine, exacerbating neuroinflammation and neuronal damage, particularly through interaction with the RAGE receptor. It is also a recognized biomarker for brain injury and is widely used in clinical practice for the early diagnosis and prognosis of traumatic brain injury, as well as in monitoring disease progression in malignant melanoma due to its secretion by tumor cells.

In research and diagnostics, S-100b’s measurement in serum or cerebrospinal fluid serves as a sensitive marker for neural distress, brain injury, and certain cancers, supporting both clinical decision-making and experimental studies on neuroinflammation and neurodegeneration.