Natural killer cells are the predominant innate lymphocyte subsets that mediate anti-tumor and anti-viral responses, and therefore possess promising clinical utilization. NK cells do not express polymorphic clonotypic receptors and utilize inhibitory receptors (KIR and Ly49) to develop, mature, and recognize ‘self’ from ‘non-self’. The essential roles of common gamma cytokines such as IL-2, IL-7, and IL-15 in the commitment and development of NK cells are well-established. However, the critical functions of proinflammatory cytokines IL-12, IL-18, IL-27, and IL-35 in the transcriptional-priming of NK cells are only starting to emerge. Recent studies have highlighted multiple shared characteristics between NK cells the adaptive immune lymphocytes. NK cells utilize unique signaling pathways that offer exclusive ways to genetically manipulate to improve their effector functions. Here, we summarize the recent advances made in the understanding of how NK cells develop, mature, and their potential translational use in the clinic.

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Natural Killer Cells: Development, Maturation, and Clinical Utilization

There is currently an unmet need for better biomarkers across the spectrum of renal diseases. In this paper, we revisit the role of Beta 2 microglobulin (β2M) as a biomarker in patients with Chronic Kidney Disease (CKD) and End Stage Renal Disease (ESRD). Prior to reviewing the numerous clinical studies in the area, we describe the basic biology of β2M, focusing in particular on its role in maintaining the serum albumin levels and reclaiming the albumin in tubular fluid through the actions of the neonatal Fc receptor. Disorders of abnormal β2M function arise as a result of altered binding of β2M to its protein cofactors and the clinical manifestations are exemplified by rare human genetic conditions and mice knockouts. We highlight the utility of β2M as a predictor of renal function and clinical outcomes in recent large database studies against predictions made by recently developed whole body population kinetic models. Furthermore, we discuss recent animal data suggesting that contrary to textbook dogma urinary β2M may be marker for glomerular rather than tubular pathology. We review the existing literature about β2M as a biomarker in patients receiving renal replacement therapy, with particular emphasis on large outcomes trials. We note emerging proteomic data suggest that β2M is a promising marker of Chronic Allograft Nephropathy. Finally, we present data about the role of β2M as a biomarker in a number of non-renal diseases. The goal of this comprehensive review is to direct attention to the multi-faceted role of β2M as a biomarker, and its exciting biology in order to propose the next steps thar are required to bring this recently rediscovered biomarkers into the 21st century.

/pdf/rediscovering-beta-2-microglobulin-as-a-biomarker-across-the-2mumxcqavk.pdf

Rediscovering Beta-2 Microglobulin As a Biomarker across the Spectrum of Kidney Diseases.

HLA-E is a nonclassical HLA class I molecule, which differs from classical HLA molecules by its nonpolymorphic, conserved nature. Expression and function of HLA-E in normal tissues and solid tumors is not fully understood. We investigated HLA-E protein expression on tissue sections of 420 ovarian and cervical cancers and found equal or higher levels than normal counterpart epithelia in 80% of the tumors. Expression was strongly associated with components of the antigen presentation pathway, e.g., transporter associated with antigen processing (TAP), endoplasmic reticulum aminopeptide (ERAP), β2 microglobulin (β2m), HLA classes I and II, and for ovarian cancer with tumor infiltrating CD8+ T lymphocytes (CTLs). This association argues against the idea that HLA-E would compensate for the loss of classical HLA in tumors. In situ detection of HLA-E interacting receptors revealed a very low infiltrate of natural killer (NK) cells, but up to 50% of intraepithelial CTLs expressed the inhibiting CD94/NKG2A receptor. In cervical cancer, HLA-E expression did not alter the prognostic effect of CTLs, most likely due to very high infiltrating CTL numbers in this virus-induced tumor. Overall survival of ovarian cancer patients, however, was strongly influenced by HLA-E, because the beneficial effect of high CTL infiltration was completely neutralized in the subpopulation with strong HLA-E expression. Interestingly, these results indicate that CTL infiltration in ovarian cancer is associated with better survival only when HLA-E expression is low and that intratumoral CTLs are inhibited by CD94/NKG2A receptors on CTLs in the tumor microenvironment.

HLA-E expression by gynecological cancers restrains tumor-infiltrating CD8+ T lymphocytes

Tumors avoid destruction by cytotoxic T cells (CTL) and natural killer (NK) cells by downregulation of classical human leukocyte antigens (HLA) and overexpression of non-classical HLA. This is the first study to investigate HLA expression in relation to histology (squamous cell carcinoma (SCC) vs. adenocarcinoma (AC)), clinicopathological parameters and survival in a large cervical cancer patient cohort. Classical (HLA-A and HLA-B/C)- and non-classical HLA molecules (HLA-E and HLA-G) were studied on primary tumors and paired lymph node (LN) metastases from cervical cancer patients (n = 136) by immunohistochemistry. The Chi2 test was used for the comparison of clinicopathological characteristics between SCC and AC patients. The Related-Samples Wilcoxon Signed Rank test was used to compare HLA expression between the primary tumor and metastasis in LN. Patient survival rates were analyzed by Kaplan-Meier curves and Log Rank test. The Mann-Whitney U Test was used to compare the distribution of HLA class I expression between SCC and AC. Decreased expression of HLA-A (SCC P < 0.001), HLA-B/C (SCC P < 0.01; AC P < 0.01) and total classical HLA (SCC P < 0.001; AC P = 0.02) was apparent in metastatic tumor cells compared to the primary tumor. In primary SCC, there was a clear trend towards complete loss of HLA-A (P = 0.05). SCC metastases showed more complete loss of HLA-A, while AC metastases showed more complete loss of HLA-B/C (P = 0.04). In addition, tumor size and parametrium involvement were also related to aberrant HLA class I expression. No significant associations between HLA expression and disease-specific (DSS) or disease-free survival (DFS) were found in this advanced disease cohort. However, in the SCC group, samples showing loss of HLA-A or loss of total classical HLA but positive for HLA-G were linked to poor patient survival (DSS P = 0.001 and P = 0.01; DFS P = 0.003 and P = 0.01, for HLA-A and total classical HLA, respectively). These results strengthen the idea of tumor immune escape variants leading to metastasis. Moreover, SCC tumors showing downregulation of HLA-A or total classical HLA in combination with HLA-G expression had poor prognosis. Our findings warrant further analysis of HLA expression as a biomarker for patient selection for CTL- and NK- cell based immunotherapeutic intervention.

https://jitc.bmj.com/content/jitc/4/1/78.full.pdf

Classical and non-classical HLA class I aberrations in primary cervical squamous- and adenocarcinomas and paired lymph node metastases

MHC class I molecules, in addition to their role in specific activation of the CTL of adaptive immune system, function also as the main ligands for NK cell inhibitory receptors, which prevent NK cells from killing normal, healthy cells. MHC class I proteins are divided into classical and nonclassical proteins. The former group consists of hundreds of HLA-A, B, and C alleles, which are universally expressed, whereas several alleles of the latter group, such as HLA-G, manifest a restricted expression pattern. Despite the important role played by these molecules in innate and adaptive immune responses, their complex expression regulation is not fully known. In our study, we investigated the regulation processes controlling the expression of MHC class I molecules, with a particular focus on their 3' untranslated regions. We identified heterogeneous nuclear ribonucleoprotein R (HNRNPR) as an important positive regulator of classical and nonclassical MHC class I molecules. HNRNPR is a RNA-binding protein belonging to the heterogeneous nuclear ribonucleoprotein family, which has a known role in processing of precursor mRNA. We demonstrated that HNRNPR binds MHC class I mRNAs in their 3' untranslated regions and enhances their stability and consequently their expression. Furthermore, regulation by HNRNPR modulates the cytotoxic activity of NK cells. In conclusion, we show that HNRNPR acts as a general positive regulator of MHC class I expression.

HNRNPR Regulates the Expression of Classical and Nonclassical MHC Class I Proteins.

The evolutionary conserved, less-polymorphic, nonclassical major histocompatibility complex (MHC) class I molecules: Qa-1 and its human homologue human leukocyte antigen-E (HLA-E) along with HLA-F, G and H cross-talk with the T-cell receptors and also interact with natural killer T-cells and other lymphocytes. Moreover, these nonclassical MHC molecules are known to interact with CD94/NKG2 heterodimeric receptors to induce immune responses and immune regulations. This dual role of Qa-1/HLA-E in terms of innate and adaptive immunity makes them more interesting. This review highlights the new updates of the mammalian nonclassical MHC-I molecules in terms of their gene organization, evolutionary perspective and their role in immunity.

Ntiya G Chakraborty

Papers

Mammalian non-classical major histocompatibility complex I and its receptors: Important contexts of gene, evolution, and immunity