Youn Soo Choi

Inside germinal centers (GCs), antigen-specific B cells rely on precise interactions with immune cells and strategic localization between the dark and light zones to clonally expand, undergo affinity maturation, and differentiate into long-lived plasma cells or memory B cells. Follicular helper T (Tfh) cells, the key gatekeepers of GC-dependent humoral immunity, exhibit remarkable dynamic positioning within secondary lymphoid tissues and rely on intercellular interactions with antigen-presenting cells (APCs) during their differentiation and execution of B-cell-facilitating functions within GCs. In this review, we briefly cover the transcriptional regulation of Tfh cell differentiation and function and explore the molecular mechanisms governing Tfh cell motility, their interactions with B cells within GCs, and the impact of their dynamic behavior on humoral responses.

Recently identified human FOXP3 ^low CD45RA ⁻ inflammatory non-suppressive (INS) cells produce proinflammatory cytokines, exhibit reduced suppressiveness, and promote antitumor immunity unlike conventional regulatory T cells (T _regs ). In spite of their implication in tumors, the mechanism for generation of FOXP3 ^low CD45RA ⁻ INS cells in vivo is unclear. We showed that the FOXP3 ^low CD45RA ⁻ cells in human tumors demonstrate attenuated expression of CRIF1, a vital mitochondrial regulator. Mice with CRIF1 deficiency in T _regs bore Foxp3 ^low INS-T _regs with mitochondrial dysfunction and metabolic reprograming. The enhanced glutaminolysis activated α-ketoglutarate–mTORC1 axis, which promoted proinflammatory cytokine expression by inducing EOMES and SATB1 expression. Moreover, chromatin openness of the regulatory regions of the Ifng and Il4 genes was increased, which facilitated EOMES/SATB1 binding. The increased α-ketoglutarate–derived 2-hydroxyglutarate down-regulated Foxp3 expression by methylating the Foxp3 gene regulatory regions. Furthermore, CRIF1 deficiency–induced Foxp3 ^low INS-T _regs suppressed tumor growth in an IFN-γ–dependent manner. Thus, CRIF1 deficiency–mediated mitochondrial dysfunction results in the induction of Foxp3 ^low INS-T _regs including FOXP3 ^low CD45RA ⁻ cells that promote antitumor immunity.

Choi J, et al. Immune Netw. 2024 Feb;24(1):e8. https://doi.org/10.4110/in.2024.24.e8

Introduction: The Middle East Respiratory Syndrome Coronavirus (MERS-CoV) is a zoonotic infectious virus that has caused significant outbreaks in the Middle East and beyond. Due to a highly mortality rate, easy transmission, and rapid spread of the MERS-CoV, it remains as a significant public health treat. There is currently no licensed vaccine available to protect against MERS-CoV.Methods: In this study, we investigated whether the proteolytic cleavage sites and fusion peptide domain of the MERS-CoV spike (S) protein could be a vaccine target to elicit the MERS-CoV S protein-specific antibody responses and confer immune protection against MERS-CoV infection. Our results demonstrate that immunization of the proteolytic cleavage sites and the fusion peptide domain using virus-like particle (VLP) induced the MERS-CoV S protein-specific IgG antibodies with capacity to neutralize pseudotyped MERS-CoV infection in vitro. Moreover, proteolytic cleavage sites and the fusion peptide VLP immunization showed a synergistic effect on the immune protection against MERS-CoV infection elicited by immunization with VLP expressing the receptor binding domain (RBD) of the S protein. Additionally, immune evasion of MERS-CoV RBD variants from anti-RBD sera was significantly controlled by anti-proteolytic cleavage sites and the fusion peptide sera.Conclusion and discussion: Our study demonstrates the potential of VLP immunization targeting the proteolytic cleavage sites and the fusion peptide and RBD domains of the MERS-CoV S protein for the development of effective treatments and vaccines against MERS-CoV and related variants.

Communication between CD4 T cells and cognate B cells is key for the former to fully mature into germinal center–T follicular helper (GC-T _FH ) cells and for the latter to mount a CD4 T cell–dependent humoral immune response. Although this interaction occurs in a B:T synapse–dependent manner, how CD4 T cells transcriptionally regulate B:T synapse formation remains largely unknown. Here, we report that Mef2d, an isoform of the myocyte enhancer factor 2 (Mef2) transcription factor family, is a critical regulator of this process. In CD4 T cells, Mef2d negatively regulates expression of Sh2d1a , which encodes SLAM-associated protein (SAP), a critical regulator of B:T synapses. We found that Mef2d regulates Sh2d1a expression via DNA binding–dependent transcriptional repression, inhibiting SAP-dependent B:T synapse formation and preventing antigen-specific CD4 T cells from differentiating into GC-T _FH cells. Mef2d also impeded IL-21 production by CD4 T cells, an important B cell help signaling molecule, via direct repression of the Il21 gene. In contrast, CD4 T cell–specific disruption of Mef2d led to a substantial increase in GC-T _FH differentiation in response to protein immunization, concurrent with enhanced SAP expression. MEF2D mRNA expression inversely correlates with human systemic lupus erythematosus (SLE) patient autoimmune parameters, including circulating T _FH –like cell frequencies, autoantibodies, and SLEDAI scores. These findings highlight Mef2d as a pivotal rheostat in CD4 T cells for controlling GC formation and antibody production by B cells.

6,8‐Diprenylorobol is a natural compound mainly found in Glycyrrhiza uralensis fisch and Maclura tricuspidata, which has been used traditionally as food and medicine in Asia. So far, the antiproliferative effect of 6,8‐diprenylorobol has not been studied yet in colon cancer. In this study, we aimed to evaluate the antiproliferative effects of 6,8‐diprenylorobol in LoVo and HCT15, two kinds of human colon cancer cells. 6,8‐Diprenylorobol inhibited the proliferation of LoVo and HCT15 cells in a dose‐ and time‐dependent manner. A 40 μM of 6,8‐diprenylorobol for 72 h reduced both of cell viability under 50%. After treatment of 6,8‐diprenylorobol (40 and 60 μM) for 72 h, late apoptotic cell portion in LoVo and HCT15 cells were 24, 70% and 13, 90%, respectively, which was confirmed by checking DNA fragmentation in both cells. Mechanistically, 6,8‐diprenylorobol activated p53 and its phosphorylated form (Ser15, Ser20, and Ser46) expression but suppressed Akt and mitogen‐activated protein kinases (MAPKs) phosphorylation in LoVo and HCT15 cells. Interestingly, 6,8‐diprenylorobol induced the generation of intracellular reactive oxygen species (ROS), which was attenuated with N‐acetyl cysteine (NAC) treatment. Compared to the control, 60 μM of 6,8‐diprenylorobol caused to increase ROS level to 210% in LoVo and HCT15, which was reduced into 161% and 124%, respectively with NAC. Furthermore, cell viability and apoptotic cell portion by 6,8‐diprenylorobol was recovered by incubation with NAC. Taken together, these results indicate that 6,8‐diprenylorobol has the potential antiproliferative effect against LoVo and HCT15 colon cancer cells through activation of p53 and generation of ROS.

Kim J, et al. Immune Netw. 2020 Jul;20(4):e35. https://doi.org/10.4110/in.2020.20.e35

Tomentosin is a natural sesquiterpene lactone extracted from various plants and is widely used as a medicine because it exhibits essential therapeutic properties. In this study, we investigated the anti-carcinogenic effects of tomentosin in human osteosarcoma MG-63 cells by performing cell migration/viability/proliferation, apoptosis, and reactive oxygen species (ROS) analysis assays. MG-63 cells were treated with various doses of tomentosin. After treatment with tomentosin, MG-63 cells were analyzed using the MTT assay, colony formation assay, cell counting assay, wound healing assay, Boyden chamber assay, zymography assay, cell cycle analysis, FITC Annexin V apoptosis assay, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, western blot analysis, and ROS detection analysis. Our results indicated that tomentosin decreased cell viability and migration ability in MG-63 cells. Moreover, tomentosin induced apoptosis, cell cycle arrest, DNA damage, and ROS production in MG-63 cells. Furthermore, tomentosin-induced intracellular ROS decreased cell viability and induced apoptosis, cell cycle arrest, and DNA damage in MG-63 cells. Taken together, our results suggested that tomentosin exerted anti-carcinogenic effects in MG-63 cells by induction of intracellular ROS.