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Per Olofsson

Licentiate thesis presentation

Time: Tue 2014-05-27 13.00 - 15.00

Location: Rum Air, SciLife Lab, Tomtebodavägen 23A, Solna

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Per Olofsson
Per Olofsson

Subject area: Cellfysik

Doctoral student: Per Olofsson , Cellens Fysik

Supervisor: Björn Önfelt

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Title

Quantitative approaches to studying NK cell functional heterogeneity

Abstract

It is commonly stated that the cell is the smallest functional unit of life.
By analogy, then, the immune cell is the smallest functional unit of the
immune system. Natural killer (NK) cells are effector cells of the innate
immune system that are responsible for mediating cellular cytotoxicity
against virally infected or neoplastically transformed cells. Many
phenotypically distinct subpopulations of NK cells have been discovered,
usually by dividing cells on the basis of cell-surface markers. These
subpopulations are typically described as related to activation or
developmental status of the cells. However, how these distinct phenotypes
correlate with behavior in e.g. NK-target interactions is less widely
understood. There is therefore a need to study NK cell behavior down at the
single-cell level. The aim of this thesis is to approach methods that
quantitatively describe these single-cell-level behavioral differences of NK
cells.

Using a newly developed single-cell imaging and screening assay, we trap
small populations of NK and target cells inside microwells, where they can
be imaged over extended periods of time. We have performed experiments on
both resting and IL-2-activated NK cells and quantified their cytotoxic
behavior. One major discovery was that a small population of NK cells
mediate a majority of the cytotoxicity directed against target cells. A
particularly cytotoxic group of cells, which we termed "serial killers",
displayed faster and more effective cytotoxicity. Also, we identified
differences between resting and activated  NK cells in regard to their
migration and contact dynamics. Activated NK cells were found to more
readily adhere to targets cells than did NK cells freshly isolated from
peripheral blood. Apart from migration and contact dynamics, we have also
quantified killing behavior, where NK cells can be seen to exhibit a
behavior we term multiple lytic hits on the basis of analyzing target cell
fluorescence profiles.

We have quantified these heterogeneities and developed tools that can be
used to further study and elucidate differences in the behavior of single
immune cells. These methods, and automated single-cell analysis methods,
will likely play a more important role in the study of immune responses in
the future.

Page responsible:Karin Lisshamre
Belongs to: Department of Applied Physics
Last changed: May 26, 2014