7.2.2.1　Polymer microspheres

Polystyrene is the most commonly used non-degradable polymer microspheres material in immunotherapy research for melanoma.Xie et al.used polystyrene microspheres and modified HLA-A2/peptide tetramer and anti-mouse CD28 monoclonal antibody on its surface.In HLA-A2/Kb transgenic mice，they could effectively proliferate antigen-specific CTLs，recognize endogenous tumor antigens expressed on the surface of human target cells and kill tumor cells in an antigen-specific way.Liang et al.amplified pTRP2-specific CTLs from C57BL/6 mouse spleen cells by co-coating H-2Kb-Ig/pTRP2 dimer complex，anti-CD28 antibody，4-1BBL and CD83 on the surface of polystyrene microspheres to target melanoma cells.

PLGA is the most commonly used degradable polymer microspheres material in research for melanoma immunotherapy.In the early 2000s，researchers demonstrated that PLGA microspheres can stably encapsulate immunomodulatory substances（e.g.，human papillomavirus 16 E7 and plasmid DNA）and deliver them safely and effectively to humans，which established the priority of PLGA microspheres in immunotherapy for melanoma.Since then，there have been growing interest in using PLGA microspheres to deliver antigens，cytokines and antibodies to increase or enhance the immune response.In 2017，Schneck et al.constructed PLGA-based artificial antigen presenting cells that are combined with anti-PD1 checkpoint inhibitors，which activated CD8+T lymphocytes and induced CD8+T lymphocytes to secrete IFN-y to the maximum extent，thereby delaying the occurrence of melanoma.(https://www.daowen.com)