Thymopentin therapy reduces the clinical severity of atopic dermatitis

Atopic dermatitis: recent trends in pathogenesis and therapy

Emerging concepts in the areas related to the pathogenesis and treatment of atopic dermatitis are reviewed. In particular, recent findings have revealed several key steps in the maintenance of a vicious circle of spongiotic dermatitis associated with elevated T-lymphocyte activation, hyperstimulatory Langerhans cells, defective cell-mediated immunity, and B-cell IgE overproduction. The discovery of specific IgE-binding structures on Langerhans cells provides a mechanism for Langerhans cells to capture and present IgE-targeted allergens to allergen-specific T cells. Furthermore, certain microbial allergens that tend to preferentially elicit IgE-type responses also elicit a T-cell response dominated by the IgE-inducing lymphokine interleukin 4. Repeated stimulation by activated Langerhans cells appears to induce just such a response. Abnormal biochemical responsiveness and mediator release by AD monocytes, mast cells, and eosinophils also participate in the sustainment or initiation of such a vicious circle, and contribute directly to the dermatitis as well. Developments in the areas of neuropeptides, genetics, microbial superantigens, and cytokine networks in the skin also appear to have promise in providing a rational link between immune defects and the inflammatory events in AD. Conventional therapy remains the mainstay of atopic dermatitis management; however, new therapies based upon the above concepts are being tested in clinical trials. Although the difficulty of objectively grading AD lesional activity and the high placebo response of AD patients hampers the interpretation of many reports, several types of approaches are coming into focus. The effectiveness of cyclosporin A, which targets T-cell activation and antigen presentation, indicates that additional agents with such activity should be effective, and verifies the criticality of these cells in AD pathogenesis. Therapy with biologic response modifiers, such as interferon gamma or thymopentin, is oriented toward normalization of imbalanced immune responsiveness, rather than direct suppression of the immune system. The mechanism of action of and toxicities of Chinese herbal mixtures require further investigation, but may reveal hitherto unconsidered avenues. Other recent therapeutic trials have focused on reduction of trigger factors, such as house dust mite exposure, foods, and the abnormal epidermal lipid barrier to irritation.

Thymopentin treatment in severe atopic dermatitis--clinical and immunological evaluations

An open clinical trial of thymopentin was conducted on 16 children with severe atopic dermatitis. The patients were treated with injections three times a week of 50 mg thymopentin for six weeks. They were then divided randomly into two groups: group A continued thymopentin for an additional six weeks, and group B were treated with normal saline. Clinical parameters and immunological function were evaluated serially. The total severity score started to decline from baseline significantly three weeks after treatment, and continued throughout the study period in group A but began to flare up in group B two weeks after stopping thymopentin. All the eight patients in group A completed the trial but three out of eight in group B dropped out because of flaring up of skin lesion. In vitro production of interleukin-4 tended to decrease and that of interferon gamma tended to increase, but total serum IgE, in vitro IgE synthesis, and abnormally low CD8+ CD11b+ suppressor T cells remained unchanged. Histamine releasing factor (HRF), plasma histamine, and respiratory burst activities of polymorphonuclear leucocytes were appreciably decreased after thymopentin treatment. It is concluded that the clinical efficacy of short term thymopentin treatment very possibly results from the decreased production of HRF and decreased release of polymorphonuclear leucocyte derived inflammatory mediators and may have no relation with antigen-IgE immune reaction.

A double-blind placebo-controlled study of thymostimulin (TP-1) for the treatment of atopic eczema

Twenty-nine patients with severe atopic eczema were entered into a randomized double-blind, placebo-controlled trial of the polypeptide thymus extract, thymostimulin (TP-1). The treatment period was 10 weeks with a subsequent follow-up period of up to 1 year. Of the 18 patients receiving TP-1 and the 11 patients on the placebo, 15 and 11 patients, respectively, were fully evaluable. There was no significant difference in either clinical or immunological status between the two treatment groups at baseline. At the 3-month follow-up clinic visit there was a statistically significant difference in the total clinical score, calculated as a percentage of baseline, in favour of the TP-1-treated patients. This difference was not maintained in the subsequent follow-up period and was not accompanied by an improvement in the patient's subjective well-being. There was no significant difference between the treatment groups with respect to the immunological parameters as measured at the 3-month clinic visit.

Atopic dermatitis: new therapeutic considerations

Atopic dermatitis is a genetically determined inflammatory condition in which the primary defect is expressed in one or more hematopoietic cells that infiltrate the skin. It is a multifactorial disease with inflammation triggered by a variety of factors. Among these, atopic dermatitis has been experimentally induced and reproduced by emotional-stress interviews and food challenges only. The inflammatory events of atopic dermatitis appear to initiated by mast cells, but eosinophils, monocytes, and T lymphocytes (predominantly CD4) also are present in lesions. The secondary effects of inflammation are a dry, brittle stratum corneum and pruritus, causing excoriation and a lichenified epidermal layer resulting from chronic rubbing. Therapeutic approaches to atopic dermatitis may be directed at several points in the evolution of the disease. Agents including emollients are needed to preserve and restore the stratum corneum barrier, and effective antipruritics are required to reduce the self-inflicted damage to the involved skin. Various other agents may be needed to antagonize mediators or cytokines and to inhibit cytokine expression and release from lesional, immune-effector cells. Likewise, new phosphodiesterase inhibitors, calcium-active agents, and antiallergic drugs may be used to reduce the quantity and pathologic functioning of inflammatory infiltrating cells in the skin.