Recombinant proteins are proteins obtained by applying recombinant DNA or RNA technology. The host cells used for producing recombinant proteins are mainly bacteria (Escherichia coli), mammalian cells, insect cells, and yeast. Recombinant proteins have been widely used in most popular research fields, including protein structure research, immune detection reagents, recombinant protein drugs, diagnostic reagent development, antibody drug targets, CAR-T cell therapy targets, Fc receptors, influenza virus proteins, and cytokines.