Normal human skin lymphocytic and Langerhans' cell responses to intradermal interferon alpha-2 beta injections

Granulomatous and suppurative dermatitis at interferon alfa injection sites: report of 2 cases

It has previously been reported that interferon alfa injection sites may develop pyoderma gangrenosum, interface dermatitis, vasculitis, or, more commonly, ulcers characterized by intravascular thrombi and a mixed inflammatory cell infiltrate. We describe 2 patients in whom granulomatous and suppurative dermatitis developed at interferon alfa injection sites. These cases extend the spectrum of interferon alfa injection site reactions. The histologic and clinical similarities of these cases with pyoderma gangrenosum and cutaneous Crohn's disease are explored.

The human hair follicle immune system: cellular composition and immune privilege

The immunology of the hair follicle, its relationship with the 'skin immune system' and its role in hair diseases remain biologically intriguing and clinically important. In this study, we analysed the immunoreactivity patterns of 15 immunodermatological markers to determine the cellular composition and immune privilege of the human hair follicle immune system in anagen VI (growth phase). The most prominent cells located in or around the hair follicle were Langerhans cells, CD4+ or CD8+ T cells, macrophages and mast cells, whereas B cells, natural killer cells and gammadelta T cells were found very rarely. Langerhans cells (CD1a+, major histocompatibility complex, MHC class II+), and T cells (CD4+ or CD8+) were predominantly distributed in the distal hair follicle epithelium, whereas macrophages (CD68+, MHC class II+) and mast cells (Giemsa+) were located in the perifollicular connective tissue sheath. Transmission electron microscopy confirmed low numbers of immune cells in the proximal hair follicle epithelium, and very few macrophages and Langerhans cells were seen in the dermal papilla. Melanophages were observed in the connective tissue sheath and dermal papilla. MHC class I (HLA-A, -B, -C) and beta2-microglobulin immunoreactivity was found on most skin cells, but was substantially reduced on isthmus keratinocytes and virtually absent in the proximal hair follicle epithelium. Apart from the absence of Fas ligand immunoreactivity, the sharply reduced numbers of T cells and Langerhans cells, and the virtual absence of MHC class I expression all suggest that the anagen proximal hair follicle constitutes an area of immune privilege within the hair follicle immune system, whose collapse may be crucial for the pathogenesis of alopecia areata.

Regression of basal cell carcinoma by intralesional interferon-alpha treatment is mediated by CD95 (Apo-1/Fas)-CD95 ligand-induced suicide

Basal cell carcinoma (BCC) is the most common skin cancer in humans, and although metastasis rarely occurs, the tumor cells are nevertheless able to invade and destroy the surrounding tissue. Intralesional injection of IFN-alpha has been found to be highly effective in inducing BCC regression by an unknown mechanism. We show that in untreated patients, BCC cells express CD95 ligand, but not the receptor, which may allow tumor expansion by averting the attack of activated CD95 receptor-positive lymphoid effector cells. The CD95 ligand of BCC cells is functional as CD95-positive cells incubated on BCC cryosections become apoptotic and are lysed. In IFN-alpha-treated patients BCC cells express not only CD95 ligand but also CD95 receptor, whereas the peritumoral infiltrate that mainly consists of CD4+ T cells predominantly contains CD95 receptor and only few CD95 ligand-positive cells. Thus, in treated patients BCC most likely regresses by committing suicide through apoptosis induction via CD95 receptor-CD95 ligand interaction.

Normal mouse skin lymphocyte, Langerhans cell, and keratinocyte responses to intradermal injections of interferon-alpha and interferon-gamma

To investigate the skin immune responses induced by intradermal injections of interferon-alpha (IFN-alpha) and interferon-gamma (IFN-gamma), normal C3H mice were injected intradermally with murine recombinant interferon-alpha (rIFN-alpha), interferon-gamma (rIFN-gamma), or the combination of rIFN-alpha and rIFN-gamma, 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-alpha (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-alpha, 6 injections of 10,000 IU rIFN-gamma failed to induce significant changes in either epidermal LGs or dermal lymphocytic infiltrates, except for an increase in dermal MOMA+ cells. High-dose rIFN-gamma 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-alpha. Furthermore, rIFN-gamma (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-alpha and rIFN-gamma failed to show synergism for induction of skin immune responses.