Interferon gamma-1b (Immunkin) is a natural chemical (or cytokine) produced by the body to help fight infections. Since it is normally made by CD4 T-cells, some experts believe that giving HIV-positive people supplementary injections of interferon gamma-1b may help them to resist infections.

Interferon gamma-1b is a licensed product for treating certain other immune deficiency diseases, but its use in people in HIV is unlicensed and experimental. It is produced by Boehringer Ingelheim under the tradename Immukin.

In laboratory tests, interferon gamma-1b had modest anti-HIV effects, but this has not been reflected in human trials. A phase I study conducted in 1989 found that it had at best mild immunological or therapeutic benefits in 16 people with AIDS, but caused significant side-effects including fever, headaches so severe that painkillers or sedation was required, fatigue, nausea and liver inflammation^[1]. A phase III trial of interferon gamma failed to show a significant effect on the rates of opportunistic infections, while giving interferon gamma-1b to patients with Kaposi’s sarcoma has had mixed results, with some patients responding to treatment, but others progressing^[2][3][4]. A study of interferon gamma-1b in HIV-infected children found that it had no effect on viral load or CD4 cell counts^[5].

Pilot research in HIV-negative people has suggested that the addition of interferon gamma to conventional treatments for mycobacterial diseases such as tuberculosis Mycobacterium avium intracellulare (MAI) may be effective in people who have developed resistance to the conventional drugs^[6][7].

Laboratory tests have found that interferon gamma inhibits the replication of Toxoplasma gondii, the cause of the brain condition toxoplasmosis, and prevents death in animals with toxoplasmosis^[8]. It also enhances the activity of anti-microbial drugs. Trials are currently assessing whether adding interferon gamma-1b to conventional toxoplasmosis treatment improves its effectiveness.