In vitro interleukin 4 and interferon-gamma production by mononuclear cells from atopic dermatitis patients

Pyrethroids and piperonyl-butoxide affect human T-lymphocytes in vitro

Synthetic pyrethroids are increasingly used as insecticides and are claimed to have a relatively low human toxicity. The aim of this study was to examine the in vitro effects of the synthetic pyrethroid S-bioallethrin alone and in combination with the common synergist piperonyl-butoxide (PBO) on human blood lymphocytes and basophils in atopic individuals and non-atopic control subjects. S-bioallethrin and PBO also caused inhibition of lymphocyte proliferation (MTT-test) after a 72-h culture period in a concentration dependent manner. In contrast to the MTT-measurements the combined agents are more effective in inhibiting interleukin-4 (IL-4)- and interferon-gamma (IFN-gamma)-production. The regulatory IL-4/IFN-gamma balance showed a significant difference between atopic and non-atopic subjects after a culture period of 24-48 h in the presence of micromolar S-bioallethrin (P < 0.001). Furthermore S-bioallethrin, PBO and the combined agents induced histamine release from human basophils. Although this effect was little compared to histamine liberators like FMLP and anti-IgE, the response to S-bioallethrin and PBO was significantly different in atopic donors compared with non-atopics (P < 0.01). In scratch test experiments 4 of 18 tested atopic volunteers showed positive reaction (wheals and flares) to S-bioallethrin and permethrin, whereas no reaction could be measured in the control group (age-matched). These findings demonstrate the immuno- and allergo-toxicological properties of the synthetic pyrethroid S-bioallethrin combined with the synergistic PBO using this in vitro approach with human lymphocytes and basophils.

In vitro effects of the pyrethroid S-bioallethrin on lymphocytes and basophils from atopic and nonatopic subjects

Synthetic pyrethroids are increasingly used as insecticides and marketed as having relatively low human toxicity. The aim of this study was to examine the in vitro effects of the synthetic pyrethroid S-bioallethrin on human blood lymphocytes and basophils in atopic individuals and nonatopic control subjects. S-bioallethrin caused inhibition of lymphocyte proliferation after a 72-h culture period in a concentration-dependent manner. The inhibition of the lymphocyte proliferation by S-bioallethrin at the concentration 6.5 microM correlated well with the total serum IgE values (r = -0.89, P < 0.001). Samples from atopic subjects were more sensitive to this inhibition than those from nonatopic volunteers. The regulatory interleukin-4/interferon-gamma (JL-4/IFN-gamma) balance showed a significant difference between atopic and nonatopic subjects after a short-term culture period (24 h) in the presence of the same concentration range of S-bioallethrin (P < 0.001). Additionally, IFN-gamma secretion was consistently lower in cells from the atopic donors. Furthermore, S-bioallethrin induced histamine release from human basophils in a concentration-dependent manner. Although the effect was small compared to histamine liberators such as N-formyl-Met-Leu-Phe and anti-IgE, the response to S-bioallethrin was significantly different in atopic donors from nonatopic (P = 0.0431). These findings are the first demonstration of the immunotoxicologic properties of the synthetic pyrethroid S-bioallethrin by this combined in vitro approach with human lymphocytes and basophils. Further studies will investigate the responses of lymphocytes from patients who are sensitive to these agents.

Interferon-gamma in the treatment of atopic dermatitis: influence on T-cell activation

Atopic dermatitis (AD) is a chronic relapsing skin disease characterized by various immunologic abnormalities. Its pathogenesis remains obscure and its treatment difficult. We have studied the efficacy of systemic recombinant human interferon-gamma (rhIFN-gamma) treatment (0.05 mg/m2 sc on 3 consecutive days, during 4 weeks) in 10 patients with severe AD. Marked clinical improvement was observed starting from the third week of treatment. Erythema, dryness, and lichenification were the most responsive symptoms. Serum immunoglobulin E and IgG4 levels did not change during treatment. Blood eosinophil count decreased only transiently at the end of the first and second series of injections (days 4 and 11; P = 0.02). Patients with AD showed an increase in CD25-positive cells (11.0% vs 4.88%; P = 0.0001) as compared to 10 age-matched healthy controls. Moreover, in parallel with clinical improvement, a distinct decrease in CD25-positive lymphocytes was observed on days 32 and 50 (P = 0.002 and P = 0.006, respectively). We suggest that in AD the beneficial effect of rhIFN-gamma might be related to the inhibition of excessive T-cell activation, perhaps of the subpopulations, producing interleukin (IL)-4 and IL-5.