Comparative analysis of NK cell receptor repertoire in adults and very elderly subjects with cytomegalovirus infection

Adaptive natural killer cell expression in response to cytomegalovirus infection in blood and solid cancer

Natural Killer (NK) cells are conventionally thought to be an indefinite part of innate immunity. However, in a specific subset of NK cells, recent data signify an extension of their "duties" in immune surveillance and response, having characteristics of adaptive immunity, in terms of persistence and cytotoxicity. These cells are known as the adaptive or memory-like NK cells, where human cytomegalovirus (HCMV) infection has been shown to drive the expansion of adaptive NKG2C+ NK cells. HCMV is a ubiquitous pathogen whose prevalence differs worldwide with respect to the socioeconomic status of countries. The adaptive NK cell subpopulation is often characterized by the upregulated expression of NKG2C, CD16, and CD2, and restricted expression of NKG2A, FCεRγ and killer immunoglobulin-like receptors (KIR), although these phenotypes may differ in different disease groups. The reconfiguration of these receptor distributions has been linked to epigenetic factors. Hence, this review attempts to appraise literature reporting markers associated with adaptive or memory-like NK cells post-HCMV infection, in relation to solid cancers and hematological malignancies. Adaptive NK cells, isolated and subjected to ex vivo modifications, have the potential to enhance anti-tumor response which can be a promising strategy for adoptive immunotherapy.

Functionally Relevant Differences in Plasma Fatty Acid Composition and Expression of Cytotoxic and Inhibitory NK Cell Receptors between Healthy Young and Healthy Elder Adults

(1) Background: In the healthy ageing, NK cell number is not modified; however, their spontaneous cytotoxicity decreases. We postulated that the age-dependent decline in metabolic activities might be responsible for this effect. (2) Methods: The fatty acid profile of 30 healthy young males (23 ± 4 years old, BMI 22.1 ± 1.3) and 30 older males (63 ± 5 years old, BMI 22.9 ± 2.5) donors were evaluated along with the expression of killing (KR) and inhibitory NK receptors (KIR) at basal level and after cultivation with fatty acids for 24 h. (3) Results: Significantly higher levels of oleic (p < 0.01), arachidonic (p < 0.001), lignoceric (p < 0.001), and nervonic acids (p < 0.0001) and significantly lower levels of docosapentaenoic and docosahexaenoic acids (p < 0.01) were found in elders as compared to young adults. At basal levels, significant (p < 0.005) differences in KR and KIR expression were encountered; 12/16 antigens. Treatment of cells with saturated fatty acids or arachidonic acid (AA) significantly enhanced KR expressions (p < 0.001). AA treatment decreased inhibitory KIR expression while docosahexaenoic, and eicosapentaenoic acid increased them. (4) Conclusions: Changes in fatty acids blood levels, and KR and KIR expression in NK cell, are age-dependent. Supplementation of NK cells with eicosapentaenoic or docosahexaenoic acid enhanced inhibitory KIR receptors’ expression which may improve their cell function.

Functional and Phenotypic Changes of Natural Killer Cells in Whole Blood during Mycobacterium tuberculosis Infection and Disease

Tuberculosis (TB) is still a global health concern, especially in resource-poor countries such as The Gambia. Defining protective immunity to TB is challenging: its pathogenesis is complex and involves several cellular components of the immune system. Recent works in vaccine development suggest important roles of the innate immunity in natural protection to TB, including natural killer (NK) cells. NK cells mediate cellular cytotoxicity and cytokine signaling in response to Mycobacterium tuberculosis (Mtb). NK cells can display specific memory-type markers to previous antigen exposure; thus, bridging innate and adaptive immunity. However, major knowledge gaps exist on the contribution of NK cells in protection against Mtb infection or TB. We performed a cross-sectional assessment of NK cells phenotype and function in four distinct groups of individuals: TB cases pre-treatment (n = 20) and post-treatment (n = 19), and household contacts with positive (n = 9) or negative (n = 18) tuberculin skin test (TST). While NK cells frequencies were similar between all groups, significant decreases in interferon-γ expression and degranulation were observed in NK cells from TB cases pre-treatment compared to post-treatment. Conversely, CD57 expression, a marker of advanced NK cells differentiation, was significantly lower in cases post-treatment compared to pre-treatment. Finally, NKG2C, an activation and imprinted-NK memory marker, was significantly increased in TST+ (latently infected) compared to TB cases pre-treatment and TST- (uninfected) individuals. The results of this study provide valuable insights into the role of NK cells in Mtb infection and TB disease, demonstrating potential markers for distinguishing between infection states and monitoring of TB treatment response.