WHY NATURAL KILLER (NK) CELLS?
Natural killer (NK) cells are lymphocytes of the innate immune system which are able to kill different targets such as cancer cells and virally infected cells without prior activation making then attractive candidates for cancer immunotherapy. Furthermore, its defence system has been extended into antimicrobial response, elimination of senescent cells, resolution of inflammation and induction of adaptive immune response. NK cells are defined as CD56+ and CD3-, which is naturally located in most of our organs and tissues, especially peripheral blood, skin, lymph nodes, bone marrow, thymus, liver, intestines, lungs, uterus etc. NK cells are classified into two distinct populations as based on surface density of CD56 expression, which are CD56bright and CD56dim NK cells and both of them have a unique functional characteristics. In brief, CD56bright NK cell represent a minimal (10%) population in the circulatory system and has low or no cytotoxic response; however this NK cell subset produces an array of cytokines and chemokines which influence the immune modulation and thus this cells are commonly referred as “cytokine producers”. On other side, CD56dim NK cell is predominant (90%) in circulatory system and is a potent mediator of natural and antibody dependent cytotoxicity.
Mechanism of Action
1. Paracrine Action
2. Recognition of the target cells
Natural killer (NK) cells can discriminate between infected and uninfected target cells and between some tumour and normal cells through sensing the appearance of MHC class I (major histocompatibility class I) molecules. Most of the nucleated normal cells express MHC class I molecules on their surface but the infected and most of the tumour cells do not express MHC class I molecules and thus the NK cell can distinguish the target cells from healthy & normal cells.
3. Killing the target cell
NK cell Killing is mediated by cytotoxic molecules which are stored within secretory lysosomes, a specialized exocytic organelle found in NK cells. Target cell recognition induces the formation of a lytic immunological synapse between the NK cell and its target. The polarized exocytosis of secretory lysosomes is then activated and these organelles release their cytotoxic contents at the lytic synapse, specifically killing the target cell.
The schematic representation shows how NK cells kill tumour cells. Normal cells are not killed because inhibitory signals from MHC class 1 molecules override the activating signals. In tumour cells or virus-infected cells, reduced expression or alteration of MHC molecules interrupts the inhibitory signals, allowing activation of NK cells and lysis of target cells. Cytokines are small cell-signalling protein molecules secreted by the immune cells to kill the cancer cells. These cytokines enter the cancer cells, disrupt their functions and eventually lysing them. Later, these dead cells are flushed out of our body through the detoxification system.
4. Migration towards target
Chemokines are chemotactic cytokines that control the migratory patterns and positioning of NK cells. NK cells can respond to a large array of chemokines and can be recruited to different points of the body and to sites of inflammation. Cytolytic CD56dim CD16bright NK cell subset expresses CXCR1, CX3CR1 and ChemR23 chemokine receptors; therefore, it is mainly recruited to inflamed peripheral tissues. Whereas, CD56bright CD16neg/dim NK cells preferentially express CCR7 and are primarily attracted by secondary lymphoid organs (lymph nodes, tonsils and spleen). These cells are highly express CD62L (L-selectin) which provides important adhesion to endothelial surfaces required for extravasation of CD56bright NK cells.
WHY MESENCHYMAL STEM CELLS (MSCS)?
NiSCELL – Immunotherapy for cancer
NiSCELL immunotherapy technology originated from Japan. However, we are continuously improving the manufacturing process to support ongoing development and clinical trials. Manufacturing human NK cell and CTL are derived from the donors of thoroughly screened qualified donors. All manufacturing activities are performed in compliance with the Good Manufacturing Practices (cGMP) standards. Our Immune cells go through a variety of tests for the period of processing and after the process to ensure the quality, sterility and potency prior to release for further use.
Mesenchymal stem cells (MSCs), are multipotent stromal cells that can differentiate into a variety of cell types and have gained a significant importance due to their potential use in tissue repair and immunosuppression. Mesenchymal stem cells are found in various adult sources initially bone marrow and later successfully isolated from various tissues such as skeletal muscle, umbilical cord, umbilical cord blood, dental pulp, adipose tissue, placenta and amniotic fluid. Despite the different origin of sources their biological characterization is almost identical.
According to the International Society of Cellular Therapy, MSCs are defined by the following three criteria (i) their adhesion to plastic; (ii) their expression of a specific set of membrane molecules (CD73, CD90, CD105), together with lack of expression of the hematopoietic markers CD14, CD34 and CD45 and human leucocyte antigen-DR (HLA-DR); and (iii) their ability to differentiate within three main pathways – osteo, adipo and chondrocytes under in-vitro (lab) conditions.
Mechanism of Action
1. Paracrine Action of MSCs
2. Immunomodulatory properties
Several pre-clinical and clinical trials reported that umbilical cord-derived MSCs are potent modulators of the immune system by suppressing primary and secondary immune cells and triggering anti-inflammatory subsets and therefore MSCs are promoted to use for therapy-resistant severe graft-versus-host disease.
3. Homing properties
MSCs have an intrinsic capacity to home to sites of injury and inflammation through chemotaxis. Chemokines released by wounds are immobilized on glycosaminoglycans on the endothelium. MSCs migrate toward this gradient, adhere and then transmigrate through the vessel wall into the wound. Systemically administrated MSCs have been detected in injured skin, eye, vasculature, heart, brain, lung, kidney, spleen, pancreas and liver. This homing is a multi-step process involving directed migration to the site of injury where MSCs adhere to the vasculature and then transmigrate from the vasculature into the injured tissue.
4. Differentiation ability
MSCs have the ability to differentiate into mesodermal lineage of adipocytes, chondrocytes and osteocytes. Despite the classical trilineage differentiation that functionally identifies MSCs, these cells have also been shown to differentiate into non-mesodermal lineages to produce cardiomyocytes, endothelial cells, hepatocytes and neural cells.
NiSCELL – Stem cell banking and process flow