Efalizumab, a novel potent regulator of T cells, is a humanized LFA-1 α subunit (CD11a) monoclonal antibody. Efalizumab has inhibitory effects on T cell activation, skin T cell transport, and T cell adhesion to keratinocytes, and can be used to study plaque psoriasis and psoriatic arthritis.

Efalizumab, at concentrations ranging from 78 ng/mL to 5 mg/mL, promotes leukocytosis and reduces the expression of LFA-1 on T cells within the peripheral blood. Additionally, at the same concentration levels, it inhibits the proliferation of peripheral blood mononuclear cells (PBMC) that is stimulated by plate-bound anti-CD3.

Efalizumab exhibits side effects including bacterial sepsis, viral meningitis, invasive fungal disease, and progressive multifocal leukoencephalopathy (PML), a brain infection caused by the reactivation of latent JC virus infection[2].