CD19 car mRNA-LNP is a lipid nanoparticle (LNP) containing CD19 car mRNA, suitable for detection of RNA delivery, translation efficiency, cell viability, etc. CD19 car mRNA can be used in chimeric antigen receptor T cell immunotherapy (CAR-CD19). The CD19 car is a chimeric antigen receptor. Among them, CD19 is a CD molecule expressed by B cells (i.e. leukocyte differentiation antigen), an important membrane antigen involved in B cell proliferation, differentiation, activation and antibody production, and can also promote BCR signal transduction[1][2].