The 4S.B3 monoclonal antibody specifically reacts with human interferon gamma, a multifunctional cytokine that is produced mainly by activated T and NK cells. Interferon gamma has anti-viral and anti-parasitic properties and plays an important role in the activation, growth, and differentiation of macrophages, B and T lymphocytes, and natural killer cells. It interacts synergically with other cytokines, such as TNF-α, to inhibit proliferation of normal and transformed cells. The 4S.B3 antibody neutralizes IFN-γ.