Interferon- (IFN-) γ is an essential cytokine for immunity against intracellular pathogens and cancer. IFN-γ expression by CD4 T lymphocytes is observed only after T helper (Th) 1 differentiation and there are several studies about the molecular mechanisms that control Ifng expression in these cells. However, naïve CD8 T lymphocytes do not produce large amounts of IFN-γ, but after TCR stimulation there is a progressive acquisition of IFN-γ expression during differentiation into cytotoxic T lymphocytes (CTL) and memory cells, which are capable of producing high levels of this cytokine. Differential gene expression can be regulated from the selective action of transcriptional factors and also from epigenetic mechanisms, such as DNA CpG methylation or posttranslational histone modifications. Recently it has been recognized that epigenetic modification is an integral part of CD8 lymphocyte differentiation. This review will focus on the chromatin status of Ifng promoter in CD8 T cells and possible influences of epigenetic modifications in Ifng gene and conserved noncoding sequences (CNSs) in regulation of IFN-γ production by CD8 T lymphocytes.

COVID‐19, caused by the SARS‐CoV‐2 virus, has become a significant global public health problem, with a wide variety of clinical manifestations and disease progression outcomes. LncRNAs are key regulators of the immune response and have been associated with COVID‐19 risk infection. Previous studies focused mainly on in‐silico analysis of lncRNA expression in the lungs or peripheral blood cells. We evaluated the expression of lncRNAs NEAT1, MALAT1, and MIR3142 in saliva and nasopharyngeal swab from SARS‐CoV‐2 positive (n = 34) and negative patients (n = 46). A higher expression of the lncRNAs NEAT1 and MALAT1 (p < 0.05) were found in positive samples. NEAT1 had a higher expression mainly in saliva samples (p < 0.001), and MALAT1 was upregulated in nasopharyngeal samples (p < 0.05). Area under the ROC curve for NEAT1 in saliva was 0.8067. This study was the first to investigate the expression of lncRNAs in saliva and nasopharyngeal samples of COVID‐19 patients, which gives new insights into the initial response to infection and infectivity and may provide new biomarkers for severity and targets for therapy.

CD8 T cells play a crucial role in immune responses to virus infections and tumors. Naïve CD8 T lymphocytes after TCR stimulation undergo differentiation into CTLs and memory cells, which are essential sources of IFN-. We investigated IFN-production by CD8 T cell subsets found in nonimmune mice. A minor fraction of in vitro TCR-stimulated CD8 T cells produce IFN-, and it is regulated at the transcriptional level. Antigen inexperienced C57BL/6 mice present the coexistence of 2 populations. The main population exhibits a CD44 low CD122 low profile, which is compatible with naïve lymphocytes. The minor expresses a phenotype of immunologic memory, CD44 hi CD122 hi. Both subsets are able to produce IL-2 in response to TCR activation, but only the memory-like population is responsible for IFN-production. Similar to memory CD8 T cells, CD44 hi CD8 + T cells also present a higher level of the transcriptional factor Eomes and a lower level of T-bet (Tbx21) mRNA than CD44 low CD8 + T cells. The presence of the CD44 hi CD8 + T cell population in nonimmune OT-I transgenic mice reveals that the population is generated independently of antigenic stimulation. CpG methylation is an efficient epigenetic mechanism for gene silencing. DNA methylation at posttranscriptional CpG sites in the Ifng promoter is higher in CD44 low CD8 + T cells than in CD44 hi CD8 + T cells. Thus, memory-like CD8 T cells have a distinct epigenetic pattern in the Ifng promoter and can rapidly produce IFN-in response to TCR stimulation.