• Prof. Dr. Joachim Koch

    Tel.: +49 69 63395-322



    Die Arbeitsgruppe von Prof. Dr. Koch ist an das Universitätsklinikum Mainz umgezogen.

    Die neue Adresse lautet:

    Prof. Dr. rer. nat. habil. Joachim Koch
    Principal investigator – Immunobiology of Natural Killer Cells
    Institute of Medical Microbiology and Hygiene
    University of Mainz Medical Center
    Hochhaus am Augustusplatz, 9th floor, room 940
    Obere Zahlbacher Str. 67
    D-55131 Mainz, Germany
    T: +49-(0) 6131-17-9336
    F: +49-(0) 6131-17-9234

    Ligand recognition and modulation of NK cell receptors

    The immune system of vertebrates relies on two branches, namely the innate and the adaptive immune system to protect an organism against infections or cancer. Whereas the components of the innate immune system, such as toxic peptides, macrophages, and natural killer (NK) cells, respond to pathogens within seconds or minutes, the adaptive immune system, which is based on B (humoral immune response) and T lymphocytes (cellular immune response) needs several days to establish. Based on these considerations, it is obvious that the innate immune system plays an important role to confine and defeat infections and cancer cells before their manifestation and thus for survival of an organism.

  • Fig. 1: A natural killer cell (NK cell, yellow) of the immune system attacking a cancer cell (red).
    (Photo courtesy of Prof. Dr. Rupert Handgretinger, Clinic for Children’s and Youth Medicine, University Hospital of Tübingen, Gemany; with permission of Eye of Science)

    NK cells comprise approximately 5-10% of the lymphocyte population in the blood, spleen, and liver and represent a transitional cell type bridging the innate and adaptive immune system. Their importance for survival is underscored by the fact that patients with NK cell deficiency suffer from severe recurrent systemic infections in general and life-threatening infections, in particular of herpes viruses such as human cytomegalovirus (HCMV). By contrast to B and T lymphocytes, NK cells are not regulated by one common receptor but by integration of numerous signals from several antagonistic surface receptors. These receptors do not undergo somatic recombination, thus identifying NK cells as part of the innate immune system. However, NK cells share a common killing mechanism with cytotoxic T lymphocytes (CTLs), which is mediated by perforin and granzymes.
    Principally, there are two categories of NK cell receptors: i) inhibitory receptors, which specifically recognize major histocompatibility complex class I (MHC I) molecules at the cell surface of body cells in order to discriminate between normal cells and cells, which have lost their surface MHC I molecules as a result of malignant transformation or viral infection, and ii) activating receptors, which trigger the cytolytic activity against malignantly transformed or virus infected cells. Activation of NK cells to kill infected or tumor cells depends on the predominance of activating signals from activating NK cell receptors.
    As a continuation of former work on MHC class I antigen presentation, our current research is focused on the investigation of receptor-ligand contacts between NK cells and target cells in order to modulate and target NK cell-mediated killing.