Engineering lymphocyte subsets: tools, trials and tribulations

Abstract

Cell-based therapies with various lymphocyte subsets hold promise for the treatment of several diseases, including cancer and disease resulting from inflammation and infection. The ability to genetically engineer lymphocyte subsets has the potential to improve the natural immune response and correct impaired immunity. In this Review we focus on the lymphocyte subsets that have been modified genetically or by other means for therapeutic benefit, on the technologies used to engineer lymphocytes and on the latest progress and hurdles in translating these technologies to the clinic.

Figure 1. Cell culture approaches for adoptive transfer of lymphocyte subsets

Culture conditions required for distinct lymphocyte subsets vary, depending on the activation and co-stimulatory requirements. a | Cytotoxic T lymphocytes (CTLs) express αβ T cell receptors (TCRs) and are stimulated by antigen-presenting cells (APCs) that express MHC class I molecules. CTLs require 4-1BB ligand (4-1BBL; also known as CD137L) stimulation for clonal expansion and have been expanded in vitro by the addition of feeder cells or artificial APCs that express the co-stimulatory ligands^–. b | CD4⁺ T cells are stimulated by APCs that express peptide-loaded MHC class II complexes. The main co-stimulatory molecule expressed by CD4⁺ T cells is CD28, which binds to CD80 or CD86 expressed on APCs. Effector CD4⁺ T cells can be stimulated by artificial APCs (aAPCs) or beads that bear CD3-specific antibody in the presence of various cytokines. Regulatory CD4⁺ T (T_Reg) cells require culturing in interleukin-2 (IL-2), and the addition of several reagents to the culture may enhance the suppressive functions of ex vivo expanded T_Reg cells. c| Cells expressing γδ TCRs, such as the Vγ9Vδ2 TCR expressed by T cells in the blood, are stimulated by APCs that present exogenous isopentenyl pyrophosphate (IPP) or other endogenous ligands stimulated by aminobisphosphonates such as zoledronate^,. d| CD1d-restricted Vα24Jα 18⁺ invaria1nt natural killer T (iNKT) cells are stimulated by α-galactosylceramide (α-GalCer) or the 6B11 clonotype-specific monoclonal antibody. FcR, Fc receptor; HDAC, histone deacetylase.