This was a multicenter, open label, ascending dose escalation study of MEDI- 507 in patients with plaque psoriasis. The objectives were to describe the safety of MEDI-507; evaluate serum concentrations of different doses; evaluate the pharmacodynamic effects on absolute lymphocyte counts and lymphocyte phenotypes and to describe the clinical grade and histolopathology of psoriasis. The first patient developed a cytokine release reaction during his first infusion. Plans were made to lower the dose, but the study was terminated.