Atopic dermatitis: The role of recombinant interferon-γ therapy

Atopic dermatitis is a common, chronic, relapsing cutaneous disease with typical cellular and humoral immunologic abnormalities that can result in significant physical and psychological morbidity to the patient. Atopic dermatitis typically begins in childhood and can often persist through adolescence into adulthood. Although there are a variety of treatments for atopic dermatitis, many patients' symptoms do not improve or they have adverse reactions to medications, requiring the search for other, effective therapeutic agents. A number of inflammatory and immunological abnormalities have long been noted in patients with atopic dermatitis. Although great strides have been made in understanding the causes, the complex pathophysiology of atopic dermatitis is still not completely understood. Most notably, patients with atopic dermatitis often have an elevation of serum immunoglobulin (Ig) E levels, depressed cellular immunity, elevated blood eosinophilia, and increased interleukin (IL)-4 production. In addition, peripheral blood mononuclear cells of patients with atopic dermatitis produce reduced levels of interferon-γ spontaneously and in response to stimuli. Due to this constellation of features, atopic dermatitis was initially viewed as a prototypical type 2 helper T lymphocyte (Th2) disease. These immunological findings led to a number of clinical trials with recombinant interferon-γ in patients who had severe, unremitting atopic dermatitis. Treatment with recombinant interferon-γ was postulated to be able to correct the immunological imbalances in patients with atopic dermatitis by decreasing serum IgE levels, IL-4 levels, restoring immune balance, and thereby leading to clinical improvement. Initial open-label studies, a double-blind placebo trial, and long-term open-label studies have demonstrated the clinical efficacy and tolerability of recombinant interferon-γ in a subset of patients with severe, unremitting atopic dermatitis. Patients receiving treatment often had marked decreases in severity of clinical parameters: erythema, edema/indurations, pruritus, excoriations, dryness, lichenification and associated reduction in total body surface area involvement. Surprisingly, treatment with recombinant interferon-γ did not lower serum IgE levels refuting the hypothesized mechanism by which interferon-γ would bring about clinical improvement in patients with atopic dermatitis. Instead, decreases were noted in absolute white blood cell and eosinophil counts that tended to correlate with clinical improvement. Although the exact mechanism by which recombinant interferon-γ brings about clinical changes in patients with atopic dermatitis is unknown, recombinant interferon-γ should be considered a possible therapy for patients with atopic dermatitis.