The hypothesis to be tested is that prevention of T-cell activation by LFA-III IgG1 fusion protein will have a beneficial therapeutic effect in patients with plaque psoriasis. A multicenter study designed by Dr. Krueger has been mounted, with plans to enroll ten patients at the Utah Center. Two-hundred patients will be enrolled in all centers, with a goal of having 160 subjects complete at least eight weeks of therapy. The agent to be tested is a dimeric protein containing the first extracellular domain of LFA-III fused to the hinged segment and constant regions of human IgG1. The LFA-III portion binds the CD2 receptor on T-cells, and the IgG1 portion binds to the Fc receptor on antigen-presenting cells. The molecule was designed to block T-cell activation by blocking the enhanced antigen-presenting capacity mediated by the co-stimulatory molecules expressed on antigen-presenting cells of the skin. Preliminary evidence suggests that the agent is safe, but efficacy data have not yet been analyzed.