Assistant Professor Sofia Johansson, Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institute, Stockholm

Title: Natural Killer cell receptor dynamics investigated with quantitative fluorescence-based techniques

Abstract: Natural Killer (NK) cells are cytotoxic lymphocytes and part of our innate immune defense. They can kill tumorigenic cells and are used clinically as immune therapy of cancer. We use a number of novel ultrasensitive fluorescence-based techniques to understand how NK cells take the decision to kill or not kill a target cell. In one project we study the diffusion of receptors within the cell membrane of cytokine-stimulated NK cells using Fluorescence Correlation Spectroscopy (FCS). We have identified a subpopulation of NK cells with much faster diffusion dynamics than the rest of the NK cells upon cytokine stimulation. A particularity of NK cells is their capability to recognize the lack of ”self” (endogenous) MHC class I expression on target cells, so-called missing-self recognition. This capability, acquired in a quantitative and highly dynamic process, is called education. What differs an educated from an uneducated NK cell, mechanistically and phenotypically, is currently unknown. By using dual-color super resolution microscopy to study clustering and co-localization of activating and inhibitory NK cell receptors, we have identified a higher degree of colocalization between activating and inhibitory receptors in human educated NK cells. These results can be used both as phenotypical markers to identify more efficient NK cells, and to better understand principles of immune cell regulation.