Functional NK Cell Cytotoxicity Assays Against Virus Infected Cells

Abstract

Natural Killer (NK) cells are crucial to the control of many viral infections. They are able to kill infected cells directly through the secretion of cytotoxic granules or through binding to death receptors on target cells. They also secrete cytokines and chemokines and, through interactions with dendritic cells, can shape adaptive immunity. The activity of NK cells can be controlled by a balance of activating and inhibitory signals conveyed through ligands on target cells binding to receptors on the NK cell. As a result viruses have devised mechanisms to modulate the expression of NK ligands on target cells, interfering with NK cell recognition and prolonging the life of infected cells. An understanding of how viruses modulate the NK response can lead to an understanding both of NK cell function, and of virus pathogenesis. Measuring the ability of NK cells to kill target cells infected with different viruses, or expressing different viral proteins, is an invaluable technique to identify the proteins and mechanisms by which viruses modulate the NK response. Here we describe two methods to measure this; one method measures sodium dichromate (51)Cr that is released from target cells as they are killed, and the other uses 7-amino-actinomycin D (7-AAD) to measure apoptosis and death of target cells following incubation with NK cells.

HLA-E-expressing pluripotent stem cells escape allogeneic responses and lysis by NK cells

“…Hematopoietic progenitors were evaluated for their susceptibility to NK cell- mediated lysis by 4 h 51 Cr release assay (adapted from 51 ). 48 h before the assay, NK cells were thawed and cultured in NK medium consisting of RPMI 1640-HEPES with 10% heat-inactivated human AB serum (Valley Biomedical), 400 U/ml IL-2 (100 U/ml IL-2 in the experiment shown in Supplementary Fig.…”

HCMV pUL135 Remodels the Actin Cytoskeleton to Impair Immune Recognition of Infected Cells

“…NK cytotoxicity was measured with Cr 51 release (Aicheler and Stanton, 2013). Degranulation assays were performed as described previously (Prod’homme et al., 2007).…”