Medical applications of interferon

The most notable medical application of IFN-y relates to the treatment of CGD, a rare genetic condition with a population incidence of between 1 in 250 00 and 1 in 1 000 000. Phagocytic cells of patients suffering from CGD are poorly capable/incapable of ingesting or destroying infectious agents such as bacteria or protozoa. As a result, patients suffer from repeated infections (Table 8.10), many of which can be life threatening. 

In addition to recurrent infection, CGD sufferers also exhibit abnormal inflammatory responses which include granuloma formation at various sites of the body (granuloma refers to a tissue outgrowth that is composed largely of blood vessels and connective tissue). This can lead to obstruction of various ducts, e.g. in the urinary and digestive tracts. 

Traditionally, treatment of CGD entailed prophylactic administration of antimicrobial agents in an attempt to prevent occurrence of severe infection. However, affected individuals still experience life-threatening infections, requiring hospitalization and intensive medical care, as often as once a year. Attempts to control these infections rely on strong antimicrobial agents and leukocyte transfusions. 

Additional molecular mechanisms must also mediate IFN-y effects, as it promotes a marked clinical improvement in some CGD patients without enhancing phagocyte activity. IFN-y s demonstrated ability to stimulate aspects of cellular and humoral immunity (e.g. via T- and B-lymphocytes), as well as NK cell activity, is most likely responsible for these observed improvements. 

IFN-y may also prove valuable in treating a variety of other conditions, and clinical trials for various indications are currently underway. This cytokine shows promise in treating leishmaniasis, a disease common in tropical and subtropical regions. The causative agent is a parasitic protozoan of the genus Leishmania. The disease is characterized by the presence of these protozoa inside certain immune cells, particularly macrophages. IFN-y appears to stimulate the infected macrophage to produce nitric oxide, which is toxic for the parasite. 

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