Ronald H. Goldfarb

Mechanisms of Tumor Cell Lysis by Natural Killer Cells

Immune reactivity against malignant cells is well-documented for a number of lymphoid cell types (1). The foremost features of anti-timor immune effector cells appears to be their capacity to recognize and subsequently kill tumor cells. Nevertheless, the mechanism(s) by which effector cells of the immune response mediate tumor cell lysis is largely unknown. The lack of precise knowledge concerning lytic pathways is evident for well studied immune killer cells, such as cytotoxic T Ijrmphocytes, as well as for effector cells that have only recently received intense experimental scrutiny, such as natural killer (NK) cells.

Chapter 26. Plasminogen Activators

Publisher Summary This chapter discusses the recent developments with an intriguing group of specific, neutral, serine proteases that proteolytically convert plasminogen, a serum zymogen, to the active enzyme plasmin: the plasminogen activators (PAs). The chapter describes the PA biochemical characterization to highlight the relationship between the molecular properties of PAs and their biological function. The association of PA and malignant cells is also emphasized as an example of the role of PAs in a variety of invasive and degradative biological processes. PAs have many regulatory functions and contribute to a number of biological degradative processes. In case of malignant cells, the expression of PA may be related to pleiotropic aspects of the malignant phenotype: invasive degradation, cell migration, cell proliferation, angiogenesis, and modification of cell surface and cytoskeletal composition. In case of thrombolytic reactivity, the degradative properties of PAs can be of importance in therapeutic lysis of clots. Recent observations, concerning the production of PA, by leukemic cells and natural killer cells, and the regulation of PA, by protease nexin, indicate that future studies may elucidate additional biological roles for the PAs.

Chapter 27. Natural Killer Cells: Role in Cell-Mediated Immunity

Publisher Summary This chapter discusses the recent findings with the most extensively studied and characterized effector cell that mediates natural immunity natural killer (NK) cells It discusses the characteristics of NK cells, the regulation of their cytotoxic potential, the role of NK cells in immune reactivity, and the potential widespread clinical relevance of the modulation of NK activity. Emphasis is placed on the role of NK cells as anti-tumor effector cells in resistance against malignant disease. Natural killer cells, a specific lymphoid subpopulation comprised of large granular lymphocytes, appear to play an important role as a natural effector cell against primary and metastatic tumor cells. Rapid advances and widespread interest in this area of cell-mediated immunity promises to fully define the role of NK cells in anti-tumor immune reactivity in the near future. Recent studies exploring the role of NK cells in a number of disease state, such as X-linked lymphoproliferative syndrome, multiple sclerosis, atopic dermatitis, as well as studies examining the in vivo reactivity of NK cells against a number of microbial agents including herpes viruses, cytomegalovirus, hepatitis virus, Babesia microti , malaria, cryptococcus, and various bacterial infections, suggests that the NK cells and natural immunity are likely to continue to receive substantial experimental and clinical attention during the next few years. Studies dealing with the role of NK cells in bone marrow transplantation reinforce this view.