Assessment of cellular immunity to human cytomegalovirus in recipients of allogeneic stem cell transplants  Simon F Lacey, Don J Diamond, John A Zaia  Biology of Blood and Marrow Transplantation  Volume 10, Issue 7, Pages 433-447 (July 2004) DOI: 10.1016/j.bbmt.2003.12.004

Figure 1 Simplified depictions of MHC-I antigen processing, T-cell receptor signaling, and detection of their consequences by 3 widely used assays of cellular immune responses. The main panel outlines in a schematic manner a simplified version of the mechanisms by which CMV antigens are processed to generate peptides and their presentation via the MHC-I pathway on the surface of antigen-presenting cells (APC). Interaction between peptide/MHC-I complexes on the APC cell surface and T-cell receptor (TCR) complexes on the surface of antigen-specific CD8+ effector lymphocytes leads via complex signal transduction pathways (abbreviated here) to increased IFN-γ production by the effector cells. The flow cytometer-based tetramer-binding assay, an example of which is shown in the top inset panel (1), uses a synthetic fluorescently conjugated probe that specifically binds T-cell receptors that have affinity for the peptide/MHC-I complex. The ICC assay (2) also uses flow cytometry after cell permeabilization and staining with fluorescent antibodies to detect cytokines such as IFN-γ and TNF-α that are produced by CD8+ effectors or CD4+ helper T lymphocytes as the result of interaction with APCs. The ELISPOT assay (3) detects these cytokines after secretion from the cells by their capture on antibody-coated culture dishes and detection with enzyme-conjugated secondary antibodies. NFAT indicates nuclear factor of activated T cells; ERK, extracellular signal-regulated kinase. Biology of Blood and Marrow Transplantation 2004 10, 433-447DOI: (10.1016/j.bbmt.2003.12.004)