polySia is involved in many natural human functions. The major examples include membranes, neuron signaling, the immune system, neutrophil extracellular trap formation, and macrophage and microglia function. First, polySia makes membrane modifications due to interactions with a variety of factors. These could include repulsive forces between the polyanionic polySia and the mostly negatively charged glycocalyx.  Because of these interactions the membrane is edited in its ability to interact with other cells, its surface charge distribution, inter-membrane interaction, pH, and membrane potential. Hydration and charge were noted before and after removing polySia from a membrane and a 25% decrease in the distance between cells was observed. This is due to the anti-adhesive properties of polySia. polySia does not only have repulsive interactions, as there are positive charge molecules located in lipid rafts, such as NCAM.  The interaction between polySia and NCAM greatly affects NCAM's signaling ability as its composition is altered when they meet. Other forms of neuron signaling polySia is involved in include brain-derived neurotrophic factor (BDNF) and fibroblast growth factor 2 (FGF2). With nearly the same mechanism, the act of polysialylation causes BDNF or FGF2 complexes through electrostatic interactions. This allows for the binding of polySia and these complexes causing polySia to be a reservoir. polySia then regulates the concentration of neurotrophins. Because they are not allowed to diffuse, signaling is more efficient. polySia is also found on immune cell surfaces. Some of the proteins are known, but many are not and the mechanisms are still being studied. However, it is known that polySia is in regulatory functions in the immune system leading to protection from invaders and response to damaged tissue. polySia is involved in NETosis which is a reactionary function of the body in the presence of foreign invaders. It is the intentional death of neutrophils. polySia ensures that this targeted cell death does not kill cells that are healthy and unaffected, as well as containing antimicrobial attributes. This is done by polySia by binding to lactoferrin, another antimicrobial molecule, surrounding neutrophils. polySia binding causes a tighter shell of lactoferrin around the cell membrane. polySia binds with Siglec-11 allowing for the regulation of microglia through exosomes. This shows that polySia binding with Siglec-11 causes a delay in neurodegeneration and control of neuroinflammation. polySia also limits inflammation in macrophages. polySia was found to have limited the expression of tumour necrosis factor (TNF).