The CD56-CD16+ NK cell subset in chronic infections

Expression of the TIGIT axis and the CD39/CD73 purinergic pathway in bone metastasis-derived immune cells

BACKGROUND

Bone metastases (BM) represent one of the most common sites of metastasis. The study aimed to compare the composition of immune cell infiltration from aspirates of different BM prior to systemic therapy.

METHOD

Phenotypic and functional analyses were conducted via multiparametric flow cytometry (MFC) on BM-derived aspirates obtained from patients with breast cancer (BC, n = 6), patients with prostate cancer (PC, n = 5), patients with non-small-cell lung cancer (NSCLC) (n = 7), patients with myeloma (MM, n = 10) and bone aspirates from age-matched non-malignant controls (NMC, n = 10).

RESULTS

Across all tumors aspirates the fraction of CD8+ T cells was reduced. In contrast, infiltration by immunosuppressive CD56+CD16-NK and CD163+CD86+ M2-like macrophages was increased in BM compared to NMC aspirates. BM-derived CD8+ T cells aberrantly co-expressed TIGIT with PVRIG or CD39. Similarly, BM-derived cytotoxic NK cells co-expressed TIGIT and PVRIG. In addition, BM-derived M2-like macrophages exhibited an increased subset of cells co-expressing either TIGIT and PVRL4 or CD112 and CD155. Using a myeloma model, functional in vitro studies showed that blockade of TIGIT and CD39 leads to increased PBMC-mediated lysis of myeloma cells.

CONCLUSION

The study shows that an altered immune cell composition is present in BM across the different tumor entities. Additionally, molecules of the TIGIT checkpoint as well as of the purinergic pathway are aberrantly expressed by BM-infiltrating CD8+ T cells, NK cells and macrophages and also functionally relevant for tumor cell lysis.

Analysis of the presence of natural killer cell subpopulations in preterm human milk: A first approach

Several immune cell populations are transferred to the newborn through breast milk, including natural killer (NK) cells, which are critical for innate defense and regulation of the immune response, especially in preterm infants. The aim of this study was to analyze the presence of NK cell subpopulations in different types of preterm breast milk. The study quantified the presence of NK cell subpopulations by flow cytometry using the relative expression of CD56 and CD16 markers in colostrum, transitional and mature milk samples from preterm mothers. Flow cytometry analysis revealed the presence of five NK cell subpopulations, but unlike those reported in peripheral blood, CD56dimCD16+ and CD56-CD16+ populations are predominantly present in preterm milk, only the CD56brightCD16dim population is increased in mature milk. Analysis of NK cell subpopulations in preterm milk revealed a pattern of NK cell presence in preterm breast milk with predominantly cytotoxic phenotypes in relation to CD16 marker expression.

Natural killer cell antibody-dependent cellular cytotoxicity to Plasmodium falciparum is impacted by cellular phenotypes, erythrocyte polymorphisms, parasite diversity and intensity of transmission

Objectives

Natural killer (NK) cells make important contributions to anti-malarial immunity through antibody-dependent cellular cytotoxicity (ADCC), but the role of different components of this pathway in promoting NK cell activation remains unclear.

Methods

We compared the functions and phenotypes of NK cells from malaria-exposed and malaria-naive donors, and then varied the erythrocyte genetic background, Plasmodium falciparum strain and opsonising plasma used in ADCC to observe their impacts on NK cell degranulation as measured by CD107a mobilisation.

Results

Natural killer cells from malaria-exposed adult Ugandan donors had enhanced ADCC, but an impaired pro-inflammatory response to cytokine stimulation, compared to NK cells obtained from malaria-naive adult North American donors. Cellular phenotypes from malaria-exposed donors reflected this specialisation for ADCC, with a compartment-wide downregulation of the Fc receptor γ-chain and enrichment of highly differentiated CD56dim and CD56neg populations. NK cell degranulation was enhanced in response to opsonised P. falciparum schizonts cultured in sickle cell heterozygous erythrocytes relative to wild-type erythrocytes, and when using opsonising plasma collected from donors living in a high transmission area compared to a lower transmission area despite similar levels of 3D7 schizont-specific IgG levels. However, degranulation was lowered in response to opsonised field isolate P. falciparum schizonts isolated from clinical malaria infections, compared to the 3D7 laboratory strain typically used in these assays.

Conclusion

This work highlights important host and parasite factors that contribute to ADCC efficacy that should be considered in the design of ADCC assays.

Association of Blood NK Cell Phenotype with the Severity of Liver Fibrosis in Patients with Chronic Viral Hepatitis C with Genotype 1 or 3

BACKGROUND

NK cells phenotype and functional state in different genotypes of chronic viral hepatitis C (CVHC), depending on liver fibrosis severity, have not been sufficiently studied, which limits the possibilities for the development of pathology therapy.

METHODS

The CVHC diagnosis was based on the EASL recommendations (2018). Clinical examination with liver elastometry was performed in 297 patients with genotype 1 and in 231 patients with genotype 3 CVHC. The blood NK cells phenotype was determined by flow cytometry in 74 individuals with genotype 1 and in 69 individuals with genotype 3 CVHC.

RESULTS

The frequency of METAVIR liver fibrosis stages F3-F4 was 32.5% in individuals with genotype 3, and 20.5% in individuals with genotype 1 CVHC (p = 0.003). In patients with both genotype 1 and genotype 3 CVHC, a decrease in the total number of blood NK cells, CD56brightCD16+ NK cells and an increase in the proportion of CD56dimCD16+ NK cells, CD94+ and CD38 + CD73+ NK cells were registered in patients with fibrosis stage F3-F4 by METAVIR in comparison with persons with METAVIR fibrosis stage F0-F1.

CONCLUSIONS

In patients with both genotype 1 and genotype 3 CVHC, an imbalance in the ratio between cytokine-producing and cytotoxic NK cells and an increase in the content of NK cells that express inhibitory molecules were determined in patients with severe liver fibrosis.

NK cell subsets and dysfunction during viral infection: a new avenue for therapeutics?

In the setting of viral challenge, natural killer (NK) cells play an important role as an early immune responder against infection. During this response, significant changes in the NK cell population occur, particularly in terms of their frequency, location, and subtype prevalence. In this review, changes in the NK cell repertoire associated with several pathogenic viral infections are summarized, with a particular focus placed on changes that contribute to NK cell dysregulation in these settings. This dysregulation, in turn, can contribute to host pathology either by causing NK cells to be hyperresponsive or hyporesponsive. Hyperresponsive NK cells mediate significant host cell death and contribute to generating a hyperinflammatory environment. Hyporesponsive NK cell populations shift toward exhaustion and often fail to limit viral pathogenesis, possibly enabling viral persistence. Several emerging therapeutic approaches aimed at addressing NK cell dysregulation have arisen in the last three decades in the setting of cancer and may prove to hold promise in treating viral diseases. However, the application of such therapeutics to treat viral infections remains critically underexplored. This review briefly explores several therapeutic approaches, including the administration of TGF-β inhibitors, immune checkpoint inhibitors, adoptive NK cell therapies, CAR NK cells, and NK cell engagers among other therapeutics.