Inclusion Criteria:  Have chronic plaque psoriasis for at least 6 months Be willing and able to undergo skin biopsies Body mass index (BMI) within the range of 18 to 40 kilograms per meter squared (kg/m²) Female participants must agree to use birth control during the study  Exclusion Criteria:  Have had certain types of infection within the last six months Have a clinically significant active infection, or recent acute active infection within the last 30 days Have other serious or unstable illnesses Have a history of organ or bone marrow transplant Have received any live vaccine within the last 4 weeks prior to screening Have received systemic nonbiologic psoriasis therapy within 4 weeks prior to study day 1 Have received topical psoriasis treatment within 14 days prior to study day 1 Have excessive skin exposure or use tanning booths for at least 4 weeks prior to study day 1