Immunological response to Parthenium hysterophorus in Indian Patients with Parthenium sensitive atopic dermatitis.

Parthenium hysterophorus is the leading cause of airborne contact dermatitis, a type IV hypersensitivity reaction in India. Though there are reports of it causing type-I hypersensitivity in atopic individuals in the form of allergic rhinitis and asthma, there is very little information on its role in pathogenesis of atopic dermatitis (AD), another predominately type I hypersensitivity. In the present study, we evaluated the presence of immediate hypersensitivity to P. hysterophorus in patients with AD and evaluated the in vitro immunological response of P. hysterophorus SPT positive AD patients to stimulation with P hysterophorus allergen. In 70 patients (age 15-45 years) with AD and 70 healthy controls, who were patch test negative to P. hysterophorus, immediate hypersensitivity to P hysterophorus was determined by skin prick test (SPT). In SPT positive patients with AD and SPT negative controls, the absolute eosinophil count (AEC), the total serum IgE and Parthenium specific IgE were determined and PBMC proliferation assay to Parthenium pollen using tritiated thymidine incorporation was done. The IL-4, IL-10, IL-2 and IFN-γ from stimulated PBMCs culture supernatant was also quantified using sandwich ELISA in both groups of patients. Twenty-five (35.7%) of 70 patients with AD had a positive SPT to Parthenium, compared to 3 (4.3%) of controls. The mean AEC, the mean total IgE and Parthenium specific IgE were significantly elevated in SPT positive AD patients vis-à-vis SPT negative controls. Similarly in the Parthenium specific PBMCs proliferation assay, the stimulation index as well as the Th2 cytokine (IL-4 and IL-10) profile were significantly elevated in SPT positive AD patients vis-à-vis SPT negative controls but there was no difference in the Th1 cytokine (IL-2 and IFN-γ) profile. Our study suggests that a third of patients with AD demonstrated a type I hypersensitivity to P. hysterophorus with a Th2 biased cytokine profile (IL-4 and IL-10) in culture supernatant of Parthenium stimulated PBMCs in these patients.