Alefacept is a fusion protein that consists of :
- the extracellular portion of human LFA3 (leukocyte function antigen 3, CD 58), that binds to the CD2 membrane receptor of T lymphocytes (especially the subset known as CD45RO+),
- linked to the Fc portion of human IgG1. This portion binds to a Fc receptor (CD16) on the membrane of immuno-competent cells, leading them to reduce activation & number of the particularly guilty subset of lymphocytes : CD45RO+.
Hence therapeutic value in psoriasis, as activated lymphocytes get rarer in the epidermis, decreasing inflammation and keratinocyte proliferation