Adhering to adhesion: assessing integrin conformation to monitor T cells

Abstract

Monitoring T cells is of major importance for the development of immunotherapies. Recent sophisticated assays can address particular aspects of the anti-tumor T-cell repertoire or support very large-scale immune screening for biomarker discovery. Robust methods for the routine assessment of the quantity and quality of antigen-specific T cells remain, however, essential. This review discusses selected methods that are commonly used for T-cell monitoring and summarizes the advantages and limitations of these assays. We also present a new functional assay, which specifically detects activated β₂ integrins within a very short time following CD8⁺ T-cell stimulation. Because of its unique and favorable characteristics, this assay could be useful for implementation into our T-cell monitoring toolbox.

Keywords: Adhesion; Function; Immunomonitoring; Immunotherapy; PIVAC 2018; T cell.

Fig. 1

Assessment of adhesion as a T-cell monitoring tool. a Principle of the assay: following T-cell receptor-mediated stimulation, integrin activation occurs within seconds through a process known as “inside-out” signaling which leads to an affinity increase and a clustering of membrane-bound integrins. Fluorescent intercellular adhesion molecule 1 multimers (mICAM-1) bind specifically to activate β₂ integrins and can be used in flow cytometry for fast monitoring and isolation of antigen-specific T cells. b Example of mICAM-1 (1.56 µg/ml) staining after 5 min activation of the blood of an HLA-A2⁺ CMV seropositive healthy donor in the absence (left) or presence (right) of the synthetic peptide NLVPMVATV (pp65-derived, HLA-A2 binding immunodominant epitope of CMV) at 4 µg/ml. Cells were stained with mICAM-1 PE, CD8 BV605, and CD3 BV510; dot plots are gated on CD3⁺CD8⁺ lymphocytes