Normal Mouse Skin Lymphocyte,Langerhans Cell,and Keratinocyte Responses to Intradermal Injections of Interferon-α and Interferon-γ

To investigate the skin immune responses induced by intradermal injections of interferon-α (IFN-α) and interferon-γ (IFN-γ), normal C3H mice were injected intradermally with murine recombinant interferon-α (rIFN-α), interferon-γ (rIFN-γ), or the combination of rIFN-α and rIFN-γ, three times per week for 2 or 4 weeks. Contralateral sites were similarly injected with placebo (saline). The results showed that after 6 or 12 injections of rIFN-α (10,000 IU/per injection), epidermal ATPase⁺ and Ia⁺ Langerhans cells (LGs) decreased significantly (p < 0.01 and p < 0.05) but dermal lymphocytic infiltrates, including CD3⁺ (pan-T cells), L3T4⁺ (T helper cells), Lyt-2⁺ (T suppressor/cytotoxic cells), MOMA⁺ (macrophages and monocytes), and dermal Ia⁺ cells, increased significantly (p < 0.01) compared with both saline injection sites and untreated skin. In contrast to rIFN-α, 6 injections of 10,000 IU rIFN-γ failed to induce significant changes in either epidermal LGs or dermal lymphocytic infiltrates, except for an increase in dermal MOMA⁺ cells. High-dose rIFN-γ injections (50,000 IU) strongly enhanced the expression of Ia antigen in epidermal keratinocytes (KCs), increased dermal lymphocytic infiltrates, and decreased the LGs in a similar pattern to that of rIFN-α. Furthermore, rIFN-γ (50,000 IU) injections induced Ia antigen expression on the KCs in the contralateral saline injection areas, suggesting a systemic effect. Injections of a combination of rIFN-α and rIFN-γ failed to show synergism for induction of skin immune responses.