Define the mechanisms underlying the short- and the long-lasting effects of IL-23 targeting in plaque PsO, by characterizing the longitudinal effects of IL-23 inhibition on the ratio of Trm/Treg cells in the skin of moderate to severe plaque PsO patients. HDST (Visium HD) and HDSP (MICS) are used to characterize the early (2 weeks) and late (16 weeks) molecular effects of treatment with tildrakizumab on the skin of three patients with moderate to severe plaque psoriasis. Non-lesional and lesional skin samples taken at the start of treatment with tildrakizumab will be used, as well as healed skin adjacent to the original sampling sites at week 2 and week 16 after the start of treatment with tildrakizumab. The same samples will be examined using Visium HD and the MACSima imaging system.

Inclusion Criteria:

• Adult patients (18 years or older) with a diagnosis of moderate to severe chronic plaque psoriasis.
• Patients eligible for treatment with an IL-23 inhibitor, specifically Tildrakizumab.

Exclusion Criteria:

• Patients unable to comply with the study requirements.
• Known hypersensitivity to IL-23 inhibitors.

The study population consists of adult patients (18 years and older) with moderate to severe plaque psoriasis. These patients have a confirmed diagnosis and are eligible for treatment with Tildrakizumab. These patients are selected from existing biobank samples with informed consent for molecular analysis related to IL-23 inhibition.