Tfh Cell Differentiation and Their Function in Promoting B-Cell Responses

Id1 expression in CD4 T cells promotes differentiation and function of follicular helper T cells and upregulation of related functional molecules

Although the roles of E proteins and inhibitors of DNA-binding (Id) in T follicular helper (TFH) and T follicular regulatory (TFR) cells have been previously reported, direct models demonstrating the impact of multiple E protein members have been lacking. To suppress all E proteins including E2A, HEB and E2-2, we overexpressed Id1 in CD4 cells using a CD4-Id1 mouse model, to observe any changes in TFH and TFR cell differentiation. Our objective was to gain better understanding of the roles that E proteins and Id molecules play in the differentiation of TFH and TFR cells. The CD4-Id1 transgenic (TG) mice that we constructed overexpressed Id1 in CD4 cells, inhibiting E protein function. Our results showed an increase in the proportion and absolute numbers of Treg, TFH and TFR cells in the spleen of TG mice. Additionally, the expression of surface characterisation molecules PD-1 and ICOS was significantly upregulated in TFH and TFR cells. The study also revealed a downregulation of the marginal zone B cell precursor and an increase in the activation and secretion of IgG1 in spleen B cells. Furthermore, the peripheral TFH cells of TG mice enhanced the function of assisting B cells. RNA sequencing results indicated that a variety of TFH-related functional molecules were upregulated in TFH cells of Id1 TG mice. In conclusion, E proteins play a crucial role in regulating TFH/TFR cell differentiation and function and suppressing E protein activity promotes germinal centre humoral immunity, which has important implications for immune regulation and treating related diseases.

Multidimensional Analysis of Lung Lymph Nodes in a Mouse Model of Allergic Lung Inflammation following PM2.5 and Indeno[1,2,3-cd]pyrene Exposure

BACKGROUND

Ambient particulate matter with an aerodynamic diameter of ≤2.5 μm (PM2.5) is suggested to act as an adjuvant for allergen-mediated sensitization and recent evidence suggests the importance of T follicular helper (Tfh) cells in allergic diseases. However, the impact of PM2.5 exposure and its absorbed polycyclic aromatic hydrocarbon (PAHs) on Tfh cells and humoral immunity remains unknown.

OBJECTIVES

We aimed to explore the impact of environmental PM2.5 and indeno[1,2,3-cd]pyrene (IP), a prominent PAH, as a model, on Tfh cells and the subsequent pulmonary allergic responses.

METHODS

PM2.5- or IP-mediated remodeling of cellular composition in lung lymph nodes (LNs) was determined by mass cytometry in a house dust mite (HDM)-induced mouse allergic lung inflammation model. The differentiation and function of Tfh cells in vitro were analyzed by flow cytometry, quantitative reverse transcription polymerase chain reaction, enzyme-linked immunosorbent assay, chromatin immunoprecipitation, immunoprecipitation, and western blot analyses.

RESULTS

Mice exposed to PM2.5 during the HDM sensitization period demonstrated immune cell population shifts in lung LNs as compared with those sensitized with HDM alone, with a greater number of differentiated Tfh2 cells, enhanced allergen-induced immunoglobulin E (IgE) response and pulmonary inflammation. Similarly enhanced phenotypes were also found in mice exposed to IP and sensitized with HDM. Further, IP administration was found to induce interleukin-21 (Il21) and Il4 expression and enhance Tfh2 cell differentiation in vitro, a finding which was abrogated in aryl hydrocarbon receptor (AhR)-deficient CD4+ T cells. Moreover, we showed that IP exposure increased the interaction of AhR and cellular musculoaponeurotic fibrosarcoma (c-Maf) and its occupancy on the Il21 and Il4 promoters in differentiated Tfh2 cells.

DISCUSSION

These findings suggest that the PM2.5 (IP)-AhR-c-Maf axis in Tfh2 cells was important in allergen sensitization and lung inflammation, thus adding a new dimension in the understanding of Tfh2 cell differentiation and function and providing a basis for establishing the environment-disease causal relationship. https://doi.org/10.1289/EHP11580.

Heterologous immunization with adenovirus vectored and inactivated vaccines effectively protects against SARS-CoV-2 variants in mice and macaques

To cope with the decline in COVID-19 vaccine-induced immunity caused by emerging SARS-CoV-2 variants, a heterologous immunization regimen using chimpanzee adenovirus vectored vaccine expressing SARS-CoV-2 spike (ChAd-S) and an inactivated vaccine (IV) was tested in mice and non-human primates (NHPs). Heterologous regimen successfully enhanced or at least maintained antibody and T cell responses and effectively protected against SARS-CoV-2 variants in mice and NHPs. An additional heterologous booster in mice further improved and prolonged the spike-specific antibody response and conferred effective neutralizing activity against the Omicron variant. Interestingly, priming with ChAd-S and boosting with IV reduced the lung injury risk caused by T cell over activation in NHPs compared to homologous ChAd-S regimen, meanwhile maintained the flexibility of antibody regulation system to react to virus invasion by upregulating or preserving antibody levels. This study demonstrated the satisfactory compatibility of ChAd-S and IV in prime-boost vaccination in animal models.

Heterologous prime-boost: breaking the protective immune response bottleneck of COVID-19 vaccine candidates

COVID-19 vaccines emerging from different platforms differ in efficacy, duration of protection, and side effects. To maximize the benefits of vaccination, we explored the utility of employing a heterologous prime-boost strategy in which different combinations of the four types of leading COVID-19 vaccine candidates that are undergoing clinical trials in China were tested in a mouse model. Our results showed that sequential immunization with adenovirus vectored vaccine followed by inactivated/recombinant subunit/mRNA vaccine administration specifically increased levels of neutralizing antibodies and promoted the modulation of antibody responses to predominantly neutralizing antibodies. Moreover, a heterologous prime-boost regimen with an adenovirus vector vaccine also improved Th1-biased T cell responses. Our results provide new ideas for the development and application of COVID-19 vaccines to control the SARS-CoV-2 pandemic.

Platycodin D attenuates airway inflammation via suppression Th2 transcription factor in a murine model of acute asthma

Introduction: Bronchial asthma is a common chronic inflammatory condition of the airway tissue. Platycodin D (PLD) has antiinflammatory effects in a mouse model of allergic asthma. In this work, the anti-asthma potential of PLD was studied by investigation of its effect to suppress airway inflammation and mucin production, a murine model of asthma and the possible mechanisms.Methods: Mice were randomly assigned to five experimental groups: control, ovalbumin (OVA), OVA+ICS (intranasal fluticasone), OVA+PLD and OVA+PLD/ICS. Airway histological studies were evaluated by the H&E staining; IL-4, IL-5, and IL-13 in bronchoalveolar lavage fluid were evaluated by ELISA; GATA3 and IRF4 mRNA of airway were measured by RT-PCR and their protein level were measured by Western blotting.Results: Our study showed that PLD suppressed eosinophilic inflammation and mucin production in bronchial mucosa. Moreover, PLD inhibited production of Th2 cytokines such as IL-4, IL-5, and IL-13. Protein production of GATA3 and IRF4, were also decreased in PLD treated OVA asthma model. Taken together, our results provided evidence that PLD inhibits the airway inflammation via suppression of Th2 transcription factor production.Conclusion: These findings suggest that PLD may effectively ameliorate the progression of asthma. These results suggest that PLD could be used as a therapy for allergic asthma.

Mechanisms of organ transplant injury mediated by B cells and antibodies: Implications for antibody-mediated rejection

Recent adjustments to the histological diagnosis and the introduction of molecular classification are providing renewed support for the paradigm that antibody-mediated rejection (ABMR) is an important clinical problem for which there is an urgent need for better therapies. Acute ABMR is observed when the graft is exposed to rapid increases in high-titer donor-specific antibodies (DSA) that are most often generated as anamnestic responses in sensitized recipients or de novo responses in nonsensitized patients who are nonadherent. Chronic ABMR is associated with slower increases in DSA, which may be high or low titer and transient or persistent. These DSA elicit cycles of injury and repair that manifest as multilamination of the peritubular capillary basement membrane or arteriopathy manifesting as intimal fibrosis. Mitigating the problem of AMBR requires the anamnestic and de novo DSA responses to be prevented and established DSA responses to be reversed. To this end, a better understanding of the immunobiology of DSA production is necessary and also the development of assays capable of detecting early humoral immune responses.Recent advances in understanding the immunobiology of B cells and areas requiring further investigation that might lead to new therapies or better diagnosis are discussed in this review.

The curious origins of angioimmunoblastic T-cell lymphoma

PURPOSE OF REVIEW

Once an obscure disease, recent studies have transformed our understanding of angioimmunoblastic T-cell lymphoma (AITL). In this review, we summarize new major advances in the genetics and biology of AITL.

RECENT FINDINGS

Genome wide sequencing studies have dissected the repertoire of the genetic alterations driving AITL uncovering a highly recurrent Gly17Val somatic mutation in the small GTPase RHOA and major role for mutations in epigenetic regulators, such as TET2, DNMT3A and IDH2, and signaling factors (e.g., FYN and CD28). These findings support a multistep model of follicular T helper cell transformation in AITL and pinpoint novel candidates for the development of targeted therapies in this disease.

SUMMARY

AITL originates from follicular T helper cells and is characterized by the presence of RHOA G17V mutation together with genetic alterations in TET2, DNMT3A, and IDH2. Research efforts now focus on the elucidation of the specific roles and interplay of these genetic alterations in the pathogenesis of AITL.

Pregnancy favors the expansion of circulating functional follicular helper T Cells

Pregnancy favors antibody production, and some evidence has suggested a direct effect of estrogen on B cells. The impact of pregnancy on circulating follicular helper T (T_FH) cells, typically identified by the expression of CD45RO and CXCR5, has not been previously investigated. Here, the percentage of T_FH cells, co-expressing or not PD-1, ICOS, or CXCR3 markers was significantly higher in pregnant women (PW) as compared with non-pregnant ones (nPW). Furthermore, the percentage of CXCR3⁺ T_FH cells able to produce IL-6, IL-21, and IL-10 was significantly higher in PW than nPW. Interestingly, anti-CMV and anti-HBs antibody titers were significantly higher in the plasma of PW and were directly correlated with IL-21-producing CXCR3⁺ T_FH cells. Finally, peripheral estrogen levels, but not progesterone, were positively related to either PD-1⁺ CXCR3⁺ T_FH cells or plasma anti-CMV and anti-HBs IgG antibodies. In summary, our data suggests a positive effect of pregnancy on the proportion of CD4⁺ T cell subset specialized in helping B cells. This phenomenon, which could be related to the high estrogen levels produced during pregnancy, may help to explain why pregnancy favor humoral immunity.

Altered circulating T follicular helper cell subsets in patients with psoriasis vulgaris

Circulating T follicular helper (Tfh) cells in the blood are counterparts to conventional Tfh cells in germinal centres. Similarly to conventional Tfh cells, circulating Tfh cells provide helpful signals for B cells. Circulating Tfh cells can be divided into three subpopulations, including Tfh17 (CXCR3-CCR6+), Tfh1 (CXCR3+CCR6-), and Tfh2 (CXCR3-CCR6-) cells, based on differences in CXCR3 and CCR6 expression. Recent studies have demonstrated that alterations in circulating Tfh cell subsets have significant effects on the progression of numerous autoimmune diseases. To address the role of circulating Tfh cells in psoriasis, we used flow cytometry to analyse frequencies of circulating Tfh cell subsets and levels of IL-21 receptor (IL-21R) expression on B cells in 32 patients with psoriasis vulgaris and 13 sex- and age-matched healthy controls. We observed dynamic changes in Tfh17 cell frequency and disease severity in 10 psoriasis patients during a 6-month treatment. Our results demonstrate that the frequency of Tfh17 cells was significantly increased in psoriasis patients and was positively correlated with psoriasis area and severity index (PASI) score, a marker of disease severity (P<0.05). During the follow-up period, the frequencies of Tfh17 cells decreased, and reductions in PASI scores were observed. Moreover, IL-21R expression on B cells was significantly increased in patients with psoriasis vulgaris (P<0.05). Interestingly, IL-21R levels on B cells were correlated with both PASI score and the frequency of Tfh17 cells (P<0.05). In conclusion, this study is the first investigation of the distribution of circulating Tfh subsets in psoriasis. These results deepen our understanding of the immune state of psoriasis patients. Our data also indicate that Tfh17 cells may not be good biomarkers for diagnosing psoriasis but may be potential biomarkers of disease severity in psoriasis.