<qa>  What is the first part of the study?The first part of the study involves NB-UVB light treatment, a well-established treatment to treat psoriasis. In the second part, we are testing a drug known as Humanized CD25 Monoclonal Antibody anti-TAC or placebo to prevent disease relapse. Anti-TAC is an injectable medicine that is also designed to treat psoriasis by blocking a part of the immune system that we believe contributes to the disease. 