Role of interferon-γ in contact hypersensitivity assessed in interferon-γ receptor-deficient mice

The role of interferon-γ (IFNγ) in contact hypersensitivity induced by the haptens, oxazolone and 2,4,6-trinitrochlorobenzene (TNCB), was investigated in mice with a targeted disruption of the IFNγ receptor (IFNγ-R-/-). The 24-h ear-swelling response to oxazolone or TNCB in sensitized animals was not significantly reduced by the disruption of IFNγ signalling. Dermal mononuclear infiltrates (MN) and epidermal microabscesses, however, were clearly diminished in the mutant mice. The hapten-induced upregulation of intercellular-adhesion molecule-1 (ICAM-1) and major histocompatibility complex (MHC) class I in IFNγ-R-/-mice was smaller when compared to wild-type mice. It is concluded that oxazolone- and TNCB-induced contact hypersensitivity is partially dependent on a functional IFNγ system. While the cutaneous oedema is IFNγ-independent, the mononuclear cell infiltration and epidermal microabscess formation are at least partly IFNγ-dependent. Therefore, reduced cellular infiltrates are likely due to a reduced upregulation of ICAM-1 and class I antigen expression in IFNγ-R-/- mice.