Study of the Frequency and of the Regulatory Function of Positive T Lymphocytes Dual CD4CD8aa (DP8a) Specific to a Bacteria of the Intestinal Microbiota (Faecalibacterium Prausnitzii) in Atopic Dermatitis, Asthma and Allergic Rhinitis

The prevalence of allergic diseases (atopic dermatitis, asthma, rhinitis, conjunctivitis and food allergy) has increased dramatically in industrialized countries over the last 20-30 years.

Allergic diseases are present especially in children and young adults, but all age groups are affected, with variations across countries and age. To propose new therapies, the investigators must first understand the physiopathology.

Since their discovery the regulatory T cells have continued to be the subject of work to understand their role in maintaining immune homeostasis in the human body but also their involvement in autoimmune diseases, inflammatory diseases, transplants of solid organs or fluids and allergic diseases.

It was identified two broad classes of regulatory T cells:

* T cells = natural regulators acquisition of a phenotype and a regulatory function right out of the thymus ( CD25 + / CD127 + low / FoxP3 +). * T cells induced regulators = acquisition of a phenotype and a regulatory function on the periphery depending on the cytokine micro-environment.

Phenotypic characterization of these is less obvious and even more so than during the last ten years several induced regulatory T cell populations have been described ( eg, Tr1 ).

A new subpopulation of T cells induced in patients with inflammatory bowel disease recently identified have a particular phenotype as bearing the CD4 and CD8 double marking with a regulatory phenotype.

These regulatory T cells are also induced a specific of a commensal intestinal bacterium (Faecalibacterium prausnitzii).

Regarding allergies, it has been widely demonstrated a relationship between changes of the intestinal microbiota and the occurrence of allergic diseases.

The investigators would therefore propose a cross-sectional study, single-center, controlled, single blinded to study the role of T cells called double positive induced regulators DP8 to compare the frequency and the regulatory function of specific DP8 of Faecalibacterium prausnitzii in atopic dermatitis, asthma and allergic rhinitis compared to control samples.