OSOBINE ĆELIJA „PRIRODNIH UBICA”

Abstract

NK (natural killer) cells comprise 10%-15% of peripheral blood mononuclear cells and have morphology of large, granular lymphocytes with the central role of killing the virus-infected and malignantly transformed cells, without prior sensitization. NK cells participate in hematopoiesis regulation, reproduction processes, as well as in numerous immune system reactions in vivo. NK cells have immunophenotyping characteristics: CD3⁻, TCR⁻, surface Ig⁻, CD56⁺, CD16⁺, CD94/NKG2D+, CD158a⁺, CD158b⁺, CD161⁺, FasL⁺. NK cells are functionally defined by percentage of lysed tumor cells previously labeled with radioactive ⁵¹Cr or by release of intracellular enzymes (LDH-lactate dehydrogenase) from destroyed target cells. NK cells employ two mechanisms for destruction of malignant cells. The first cytotoxic mechanism is spontaneous and major histocompatibility antigen independent process, while the second mechanism is antibody dependent cellular cytotoxicity (ADCC). After activation, NK cells release the following proteolytic enzymes: perforin, serine esterase (granzymes A and B) chondroitin sulphate, phospholipases and other lytic molecules, and destroy malignantly transformed cells by necrotic process. However, NK cells exhibit their effector mechanisms also through apoptosis by non-secretory mechanism mediated by TNF receptor superfamily members. NK cells have stage-dependent lower activity in different tumor.

Keywords: NK cell; immunophenotype; activation; effector mechanisms; apoptosis; necrosis