In the absence of heparan sulfate the presence of the D1 sequence increases the rate at which IFN-γ-receptor complexes form. Interactions between the D1 cluster of amino acids and the receptor may be the first step in complex formation. By binding to D1 HS may compete with the receptor and prevent active receptor complexes from forming. The biological significance of heparan sulfates interaction with IFN-γ is unclear; however, binding of the D1 cluster to HS may protect it from proteolytic cleavage. Biological activity
IFN-γ is secreted by T helper cells (specifically, Th1 cells), cytotoxic T cells (TC cells), macrophages, mucosal epithelial cells and NK cells. IFN-γ is both an important autocrine signal for professional APCs in early innate immune response, and an important paracrine signal in adaptive immune response. The expression of IFN-γ is induced by the cytokines IL-12, IL-15, IL-18, and type I IFN. IFN-γ is the only Type II interferon and it is serologically distinct from Type I interferons; it is acid-labile, while the type I variants are acid-stable. IFN-γ has antiviral, immunoregulatory, and anti-tumor properties. It alters transcription in up to 30 genes producing a variety of physiological and cellular responses. Among the effects are:

Promotes NK cell activity
Increases antigen presentation and lysosome activity of macrophages.
Mechanism
The Bennett fracture is an oblique intraarticular metacarpal fracture dislocation, caused by an axial force directed against the partially flexed metacarpal. This type of compression along the metacarpal bone is often sustained when a person punches a hard object, such as the skull or tibia of an opponent, or a wall. It can also occur as a result of a fall onto the thumb. This is a common injury sustained from bike falls, as the thumb is generally extended while around the handle bars. It is also a common injury in car crashes, especially into fixed objects, from the driver holding the steering wheel during impact. The hand moves forward, while the steering wheel rim hyperextends the thumb. Some authors have recently made an assertion against popular belief that the APL tendon is not a deforming force on the Bennett fracture. Treatment
Though these fractures commonly appear quite subtle or even inconsequential on radiographs, they can result in severe long-term dysfunction of the hand if left untreated. In his original description of this type of fracture in 1882, Bennett stressed the need for early diagnosis and treatment in order to prevent loss of function of the thumb CMC joint, which is critical to the overall function of the hand. In the most minor cases of Bennett fracture, there may be only small avulsion fractures, relatively little joint instability, and minimal subluxation of the CMC joint (less than 1 mm).