Programmed cell death and natural killer cells in multiple sclerosis: new potential therapeutic targets?

The role of KIR positive NK cells in diseases and its importance in clinical intervention

Natural killer (NK) cells are essential for the elimination of the transformed and cancerous cells. Killer cell immunoglobulin-like receptors (KIRs) which expressed by T and NK cells, are key regulator of NK cell function. The KIR and their ligands, MHC class I (HLA-A, B and C) molecules, are highly polymorphic and their related genes are located on 19 q13.4 and 6 q21.3 chromosomes, respectively. It is clear that particular interaction between the KIRs and their related ligands can influence on the prevalence, progression and outcome of several diseases, like complications of pregnancy, viral infection, autoimmune diseases, and hematological malignancies. The mechanisms of immune signaling in particular NK cells involvement in causing pathological conditions are not completely understood yet. Therefore, better understanding of the molecular mechanism of KIR-MHC class I interaction could facilitate the treatment strategy of diseases. The present review focused on the main characteristics and functional details of various KIR and their combination with related ligands in diseases and also highlights ongoing efforts to manipulate the key checkpoints in NK cell-based immunotherapy.

KIR2DL4-HLAG interaction at human NK cell-oligodendrocyte interfaces regulates IFN-γ-mediated effects

Interactions between germline-encoded natural killer (NK) cell receptors and their respective ligands on tumorigenic or virus-infected cells determine NK cell cytotoxic activity and/or cytokine secretion. NK cell cytokine responses can be augmented in and can potentially contribute to multiple sclerosis (MS), an inflammatory disease of the central nervous system focused upon the oligodendrocytes (OLs). To investigate mechanisms by which NK cells may contribute to MS pathogenesis, we developed an in vitro human model of OL-NK cell interaction. We found that activated, but not resting human NK cells form conjugates with, and mediate cytotoxicity against, human oligodendrocytes. NK cells, when in conjugate with OLs, rapidly synthesize and polarize IFN-γ toward the OLs. IFN-γ  is capable of reducing myelin oligodendrocyte and myelin associated glycoproteins (MOG and MAG) content. This activity is independent of MHC class-I mediated inhibition via KIR2DL1, but dependent upon the interaction between NK cell-expressed KIR2DL4 and its oligodendrocyte-expressed ligand, HLA-G. NK cells from patients with MS express higher levels of IFN-γ following conjugation to OLs, more actively promote in vitro reduction of MOG and MAG and have higher frequencies of the KIR2DL4 positive population. These data collectively suggest a mechanism by which NK cells can promote pathogenic effects upon OLs.

Multiple sclerosis is accompanied by lack of KIR2DS1 gene: A meta-analysis

Multiple sclerosis (MS) is a disease in which we can recognize destruction of the myelin that is around nerve cells of brain and spinal cord called as oligodendrocytes. Both genetic and environmental factors play roles in MS. One of these genes is the killer-cell immunoglobulin-like receptor (KIR) which expressed on surface of natural killer cells (NKs). These genes have loci (not locus) in human genome, so they inherit as haplotypes. The results of previous studies show that different genes of KIR may affect both susceptibility and resistance to such autoimmune disorders that their pathogenesis in MS is still unclear. Since NKs play key roles in immune tolerance, we intend to perform a meta-analysis for the correlation of KIR genes and MS. We used the software comprehensive meta-analysis for data of totally 568 MS patients and 280 controls. Among the 14 genes of KIR in the human genome, lack of KIR2DS1 is accompanied by MS. No KIR gene found to be a risk factor for MS. Further studies on other molecules of NKs like CD94 and NKG2a is suggested.