Biological agents are classified according to their mechanism of action: 1. those that inhibit T-cell activation, such as efalizumab; 2. those that inhibit certain inflammatory cytokines, such as etanercept, infliximab, etc. The main biological agents used for psoriasis treatment are as follows: ① Alfacercept (alefacept, LFA-3Tip, Amevive): It is a drug that reduces pathogenic T cells. In addition, the IgG region of alefacept binds to FcrIII receptors on cells such as macrophages and natural killer cells resulting in selective apoptosis of memory T lymphocytes. The main disadvantage is that only 50% or less of those with severe disease are in remission. ② Ontak (denileukin diftifox, DAB389 IL-2, Ontak): It can selectively kill activated T cells, and its adverse effects are chills, fever, malaise, nausea, vomiting, and also acute allergic reactions can occur. (iii) Infliximab (Remicade): kills TNF-α-containing cells on the membrane surface through cytotoxic effects, and also induces apoptosis of activated T cells. In unstable erythrodermic or pustular psoriasis, it can rapidly control the disease. Compared with methotrexate, it has no nephrotoxicity and hepatotoxicity, and its disadvantage is that it must be injected slowly. ④Esercept (etanercept, Enbrel, Immune): It works by binding to TNF and thus blocking it. It can effectively treat moderate and severe psoriasis, erythrodermic psoriasis, psoriatic arthritis and certain intractable psoriasis, and is one of the most promising drugs for the treatment of moderate to severe psoriasis. ⑤ Ciprilizumab (siplizumab, MEDI-507): mainly inhibits T-cell activity through CD2, while Hum291, a humanized product of OKT3, binds to CD3 on T cells and induces an apoptotic mechanism to selectively remove antigen-reactive T cells, and also regulates between the two types of responses by reducing TH1-type cytokines as well as increasing TH2-type cytokines The balance between the two types of responses is also regulated by reducing TH1-type cytokines and increasing TH2-type cytokines. (6) Efalizumab (hull24, efalizumab, Xanelim): The therapeutic effect is achieved by blocking the interaction of LFA-l on the surface of T cells with CD54 on the surface of antigen-presenting cells, vascular endothelium and keratinocytes, reducing the migration of T cells into the lesion and inhibiting the secretion of pro-inflammatory cytokines in the lesion. (7) Others: e.g. anti-CD4 antibody (OKTcdr4a, imuclone): inhibits T-cell activation by binding to CD4 in the T-cell receptor (TCR) complex. Recombinant human interleukin 10 (tenovil, rhIL-10, Ten2ovil) is an immunomodulatory cytokine that normalizes abnormally proliferating and differentiated keratin-forming cells. Recombinant human interleukin-11 is a multifunctional cytokine that plays an important role in the regulation of bone marrow hematopoiesis and can act directly on macrophages, thereby reducing the production of inflammatory factors such as TNF-α, IL-1β and IL-12p40, and is also starting to be used in the treatment of psoriasis. The efficacy of biological agents on psoriasis varies, and their clinical application is limited by factors such as more expensive drugs, still unable to solve the problem of relapse, and some biological agents have obvious side effects.