Summary Both conventional T (Tconv) cells and regulatory T (Treg) cells are activated through ligation of the T cell receptor (TCR) complex, leading to the induction of the transcription factor NF-κB. In Tconv cells, NF-κB regulates expression of genes essential for T cell activation, proliferation and function. However the role of NF-κB in Treg function remains unclear. We conditionally deleted canonical NF-κB members p65 and c-Rel in developing and mature Treg cells and found they have unique but partially redundant roles. c-Rel was critical for thymic Treg development while p65 was essential for mature Treg identity and maintenance of immune tolerance. Transcriptome and NF-κB p65 binding analyses demonstrated a lineage specific, NF-κB-dependent transcriptional program, enabled by enhanced chromatin accessibility. These dual roles of canonical NF-κB in Tconv and Treg cells highlight the functional plasticity of the NF-κB signaling pathway and underscores the need for more selective strategies to therapeutically target NF-κB.

We revealed that a novel adipokine, FAM19A5, was capable of inhibiting postinjury neointima formation via sphingosine-1-phosphate receptor 2-G12/13-RhoA signaling. Downregulation of FAM19A5 during obesity may trigger cardiometabolic diseases.

Cytokines are soluble proteins that exert their functions by binding specific receptors. Many cytokines play essential roles in carcinogenesis and have been developed for the treatment of cancer. In this study, we identified a novel potential cytokine using immunogenomics designated colon-derived SUSD2 binding factor (CSBF), also known as chromosome 10 open reading frame 99 (C10orf99). CSBF/C10orf99 is a classical secreted protein with predicted molecular mass of 6.5 kDa, and a functional ligand of Sushi Domain Containing 2 (SUSD2). CSBF/C10orf99 has the highest expression level in colon tissue. Both CSBF/C10orf99 and SUSD2 are down-regulated in colon cancer tissues and cell lines with different regulation mechanisms. CSBF/C10orf99 interacts with SUSD2 to inhibit colon cancer cell growth and induce G1 cell cycle arrest by down-regulating cyclin D and cyclin-dependent kinase 6 (CDK6). CSBF/C10orf99 displays a bell-shaped activity curve with the optimal effect at ~10 ng/ml. Its growth inhibitory effects can be blocked by sSUSD2-Fc soluble protein. Our results suggest that CSBF/C10orf99 is a novel potential cytokine with tumor suppressor functions.

To date, IgG in the tumor microenvironment (TME) has been considered a product of B cells and serves as an antitumor antibody. However, in this study, using a monoclonal antibody against cancer-derived IgG (Cancer-IgG), we found that cancer cells could secrete IgG into the TME. Furthermore, Cancer-IgG, which carries an abnormal sialic acid modification in the CH1 domain, directly inhibited effector T-cell proliferation and significantly promoted tumor growth by reducing CD4 + and CD8 + T-cell infiltration into tumor tissues. Mechanistic studies showed that the immunosuppressive effect of sialylated Cancer-IgG is dependent on its sialylation and binding to sialic acid-binding immunoglobulin-type lectins (Siglecs) on effector CD4 + and CD8 + T cells. Importantly, we show that several Siglecs are overexpressed on effector T cells from cancer patients, but not those from healthy donors. These findings suggest that sialylated Cancer-IgG may be a ligand for Siglecs, which may serve as potential checkpoint proteins and mediate tumor immune evasion.

Gene expression is highly dynamic and plastic. We present a new immunological database, ImmuSort. Unlike other gene expression databases, ImmuSort provides a convenient way to view global differential gene expression data across thousands of experimental conditions in immune cells. It enables electronic sorting, which is a bioinformatics process to retrieve cell states associated with specific experimental conditions that are mainly based on gene expression intensity. A comparison of gene expression profiles reveals other applications, such as the evaluation of immune cell biomarkers and cell subsets, identification of cell specific and/or disease-associated genes or transcripts, comparison of gene expression in different transcript variants and probe set quality evaluation. A plasticity score is introduced to measure gene plasticity. Average rank and marker evaluation scores are used to evaluate biomarkers. The current version includes 31 human and 17 mouse immune cell groups, comprising 10,422 and 3,929 microarrays derived from public databases, respectively. A total of 20,283 human and 20,963 mouse genes are available to query in the database. Examples show the distinct advantages of the database. The database URL is http://202.85.212.211/Account/ImmuSort.html.

PC3-secreted microprotein (PSMP) or microseminoprotein is a newly discovered secreted protein whose function is currently unknown. In this study, PSMP was found to possess chemotactic ability toward monocytes and lymphocytes, and its functional receptor was identified as CCR2B. PSMP was identified as a chemoattractant protein from a PBMC chemoattractant platform screen that we established. The mature secreted PSMP was able to chemoattract human peripheral blood monocytes, PBLs, and CCR2B-expressing THP-1 cells, but not peripheral blood neutrophils, even though it does not contain the classical structure of chemokines. CCR2B was identified as one receptor for PSMP-mediated chemotaxis by screening HEK293 cells that transiently expressed classical chemokine receptors; results obtained from the chemotaxis, calcium flux, receptor internalization, and radioligand-binding assays all confirmed this finding. To further identify the major function of PSMP, we analyzed its expression profile in tissues. PSMP is highly expressed in benign prostatic hyperplasia and in some prostate cancers, and can also be detected in breast tumor tissue. In response to PSMP stimulation, phosphorylated ERK levels downstream of CCR2B signaling were upregulated in the PC3 cell line. Taken together, our data collectively suggest that PSMP is a chemoattractant protein acting as a novel CCR2 ligand that may influence inflammation and cancer development.

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Antibodies have a common structure consisting of two identical heavy (H) and two identical light (L) chains. It is widely accepted that a single mature B cell produces a single antibody through restricted synthesis of only one VHDJH (encoding the H-chain variable region) and one VLJL (encoding the L-chain variable region) via recombination. Naive B cells undergo class-switch recombination (CSR) from initially producing membrane-bound IgM and IgD to expressing more effective membrane-bound IgG, IgA, or IgE when encountering antigens. To ensure the “one cell — one antibody” paradigm, only the constant region of the H chain is replaced during CSR, while the rearranged VHDJH pattern and the L chain are kept unchanged. To define those long-standing classical concepts at the single-cell transcriptome level, we applied the Chromium Single-Cell Immune Profiling Solution and Sanger sequencing to evaluate the Ig transcriptome repertoires of single B cells. Consistent with the “one cell — one antibody” rule, most of the B cells showed one V(D)J recombination pattern. Intriguingly, however, two or more VHDJH or VLJL recombination patterns of IgH chain or IgL chain were also observed in hundreds to thousands of single B cells. Moreover, each Ig class showed unique VHDJH recombination pattern in a single B-cell expressing multiple Ig classes. Together, our findings reveal an unprecedented presence of multi-Ig specificity in some single B cells, implying regulation of Ig gene rearrangement and class switching that differs from the classical mechanisms of both the “one cell — one antibody” rule and CSR.