Role of regulatory T cells in the pathogenesis of atopic dermatitis and psoriasis vulgaris.

Atopic dermatitis (AD) is a chronic relapsing skin disease that causes highly
itching erythematous lesions. The pathogenesis of AD is incompletely
understood. Dysregulated immunological responses, skin barrier dysfunction,
genetic predilection and environmental factors ultimately lead to sensitization
and influx of T lymphocytes. Regulatory T cells (Tregs) are pivotal in
controlling inflammatory responses. The importance of Tregs in maintaining
immunological homeostasis in the skin is underlined by the strong association
of AD with IPEX (immune dysregulation, polyendocrinopathy enteropathy X-linked
syndrome) a x-linked immunological disorder caused by mutation in the FOXP3
gene. However, conflicting data exist about their presence and function in AD
skin.
Previous studies have studied the function of Tregs in AD and healthy control
skin that were isolated from peripheral blood. However, these Tregs may not be
representative of those present in (inflamed) skin. Therefore, we will use
(short-term) skin explants to isolate Tregs directly from skin biopsies.

Psoriasis vulgaris (PV) is another chronic skin disease that presents with
disfiguring erythematous and scaly lesions. Its pathogenesis is not yet fully
understood. But, like in atopic dermatitis, the main key effector cells seem to
be T cells. Tregs are present in psoriasis vulgaris skin. However, Tregs
isolated from peripheral blood of psoriasis patients have diminished
suppressive capacities. As for AD, it will be useful to study the function of
Tregs that are isolated directly from the inflamed psoriasis skin.

To determine the functional capacities of regulatory T cells present in
lesional and non-lesional atopic dermatitis skin, and lesional and non-lesional
psoriasis vulgaris skin.

observational study

Patients and healthy controls will have to visit the outpatient department for
one visit. During this visit 2 skin punch biopsies (4 mm diameter) from
lesional and 2 skin punch biopsies (4 mm diameter) from non-lesional skin will
be taken. Risks of skin biopsies include infection and the formation of a
(hypopigmented) scar. Furthermore, we will draw 40 ml of blood (4 vials) with
one venapunction. To determine disease severity a physical examination will be
done to assess a SCORAD and LSS in case of AD patients and a PASI in case of
psoriasis patients.
In order to optimize our assays we will use skin that is left over from plastic
surgery. Patients will be called an asked to participate in this study. From
these patients blood (40 ml) will be obtained at the outpatient blood lab.