Natural Killer Cell Phenotypes and Functions in Multiple Sclerosis

Christian Münz, Ph.D.

Rockefeller University

Funded in September, 2006: $200000 for 3 years
LAY SUMMARY . ABSTRACT . BIOGRAPHY .

LAY SUMMARY

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Do Immune Natural Killer Cells Play a Pivotal Role in Autoimmune Multiple Sclerosis?

Researchers will determine whether faulty immune “natural killer” (NK) cells sustain the central nervous system (CNS) destruction that occurs in people with autoimmune multiple sclerosis (MS).  If so, findings may lead to development of new MS therapies that target NK cells.

Why immune cells destroy nerve cells in the brain and spinal cord in people with MS remains an elusive question.  The researchers suspect, however, that faulty NK cells play a key role. NK cells are part of the “innate” immune system.  This system ordinarily mounts a rapid, generalized response against invaders, and marshals specialized “adaptive” immune cells to attack.  As part of this innate system, NK cells ordinarily confer protection by killing infected cells and by producing substances that inhibit infectious agents and cancer cell growth. While both of these functions are accomplished by the same NK cells in rodents, humans have two NK cell subtypes, each performing one of these tasks. Human studies of their actions in autoimmune MS, therefore, are essential. The researchers hypothesize that NK cells sustain destructive autoimmunity in MS by shaping responses of adaptive immune T cell attackers, and by directly recognizing and killing CNS cells that have been damaged in these attacks. 

They will test this hypothesis by  identifying processes that NK cells use to recognize and kill human brain cells; determining whether NK cells, along with innate “dendritic” cells and “microglia,” are capable of shaping local adaptive immune cell responses within the CNS; and investigating whether NK cells in MS patients participate in formation of CNS inflammation that is associated with patients’ clinical symptoms.

Significance:  If this study determines the role of innate immune NK cells in autoimmune MS, the findings could lead to development of therapies that target NK cells to prevent their actions.

ABSTRACT

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Natural Killer Cell Phenotypes and Functions in Multiple Sclerosis

Natural killer (NK) cells are multicompetent lymphocytes of the innate immune system, whose central role in host defense, immune regulation, and autoimmunity has been increasingly recognized in the last years.

The NK cell physiology differs significantly between humans and rodents. Humans harbor two functionally distinct NK cell subsets exerting either predominantly cytolytic (CD16+CD56dim) or immunoregulatory (CD16-CD56bright) functions and utilize different receptors for NK cell activation and inhibition. The overall goal of this proposal is to define and understand the multiple roles of natural killer (NK) cells in the evolution and progression of (auto)immune-mediated damage of the human CNS with a primary focus on multiple sclerosis (MS). The hypothesis to be tested is that NK cells enhance inflammatory CNS diseases in humans, and play a pivotal role in sustaining destructive autoimmunity in MS by (i) shaping local Th1-polarized adaptive immune responses within the target tissue and via (ii) direct recognition and lysis of inflammation-activated human brain cells.

This proposal takes advantage of the respective expertises of Dr. Christian Münz (PI, Rockefeller University, New York) in immunology and innate immunity with a focus on NK cell biology, Dr. Cedric Raine (collaborator, Albert Einstein College of Medicine, New York) in neuropathology and neuroimmunology, and Dr. Fred Lublin (collaborator, Mount Sinai School of Medicine, New York) in neurology and multiple sclerosis research.

To achieve our objective, three Specific Aims are proposed: 

1. To identify the mechanism by which NK cells recognize and kill human brain cells. Cytotoxicity will be determined in co-culture experiments using human fetal brain tissue–derived target cells (oligodendrocytes, microglial, astrocytes) and human NK cells in titrated effector cell to target cell (E:T) ratios. Transwell and blocking experiments will define the mechanisms by which NK cells induce CNS tissue injury in humans.

2. To determine whether NK cells are capable of shaping local adaptive immune responses within the CNS via interaction with microglial and dendritic cells (DC). The phenotypic plasticity of human quiescent and differentiated microglial cells (MG) in response to classical DC stimuli will be determined by multiparameter flow-cytometry. Co-culture with activated and phenotypically characterized human NK cells in titrated E:T ratios will determine whether NK-DC/MG interactions can directly induce DC/MG maturation. The stimulatory capacity of matured MGs and DCs will be tested by cytokine staining and in primary alloreactive T cell responses. Transwell and blockade experiments will define the mechanisms by which NK cells exert immunoregulatory effects on human MG and DC.

3. To investigate whether and to which extent NK cells participate in the formation of inflammatory CNS lesions in vivo, and to correlate NK cell phenotypes and functions in the peripheral blood and the cerebrospinal fluid (CSF) with clinical disease parameters in patients with MS and other inflammatory neurological diseases.

The proposed research aim will take advantage of the unique opportunity to study a broad set of human post mortem CNS tissue samples for the presence and distribution of NK cells in the diseased brain at the laboratory of Dr. Cedric Raine. Complementing our mechanistic in vitro-studies outlined in Specific Aims #1 and #2, cryopreserved brain samples derived from patients with MS and other CNS diseases will be characterized for the presence, distribution, and phenotype of NK cells in inflammatory brain lesions. In addition, we will characterize phenotypes and functions of NK cell derived from the blood and the CSF of patients with MS, and correlate our findings with clinical disease parameters.

Accomplishing the specific aims and the integration of the approaches outlined in this proposal might help in understanding how innate lymphocytes could sustain destructive autoimmunity in MS and will potentially provide us with a rationale for novel therapeutic strategies targeting the innate immune system in inflammatory brain diseases.

INVESTIGATOR BIOGRAPHIES

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Christian Münz, Ph.D.

Dr. Christian Münz is Assistant Professor and Head of the Laboratory of Viral Immunobiology at the Rockefeller University in New York. He received his undergraduate degree in human medicine and masters degree in biochemistry in 1995 from the University of Tübingen in Germany. He received his Ph.D. in 1998 from the German Cancer Research Center in Heidelberg and the Institute for Cell Biology at the University of Tübingen. He came to the Rockefeller University in 1998 as a postdoctoral fellow in the Laboratory of Cellular Physiology and Immunology. He was named research assistant professor in 2001, and assistant professor and head of the Laboratory of Viral Immunobiology in 2003.

Dr. Münz was awarded a special fellowship from the Leukemia & Lymphoma Society in 2001 and the Speaker’s Fund Award for Public Health Research of the New York Academy of Medicine in 2002. In 2005 he received a Beckman Young Investigator Award from the Arnold and Mabel Beckman Foundation, and was named a Sinsheimer Scholar by the Alexandrine and Alexander Sinsheimer Fund. He received a Burroughs Wellcome Fund Investigators in Pathogenesis of Infectious Disease Award and the DANA Foundation’s Neuroimmunology Award in 2006.

Research in the Münz Laboratory focuses on the immune control of the human tumorvirus Epstein Barr virus (EBV), primarily the interaction of the innate lymphocytes dendritic cells and natural killer cells at the onset of immune responses, and antigen recognition as well as protective function of virus specific CD4+ T cells. Dr. Münz and his colleagues compare immune responses of healthy virus carriers with patients in which this immune control fails or is deregulated. This research focuses primarily on Burkitt’s and Hodgkin’s lymphoma as EBV-associated malignancies, and Multiple Sclerosis (MS), as an autoimmune disease associated with elevated EBV specific immune responses. In MS, both adaptive CD4+ T cell immunity as well as DC/NK cell interactions are under investigation. A better understanding of the comprehensive immune control of the persistent Epstein Barr virus and its failure in diseases should allow for the development of immunotherapies against this oncogenic pathogen.