The Potential of Harnessing IL-2-Mediated Immunosuppression to Prevent Pathogenic B Cell Responses

Interleukin-2-secreting T helper cells promote extra-follicular B cell maturation via intrinsic regulation of a B cell mTOR-AKT-Blimp-1 axis

During antigen-driven responses, B cells can differentiate at extra-follicular (EF) sites or initiate germinal centers (GCs) in processes that involve interactions with T cells. Here, we examined the roles of interleukin (IL)-2 secreted by T helper (Th) cells during cognate interactions with activated B cells. IL-2 boosted the expansion of EF plasma cells and the secretion of low-mutated immunoglobulin G (IgG). Conversely, genetically disrupting IL-2 expression by CD4+ T cells, or IL-2 receptor (CD25) expression by B cells, promoted B cell entry into the GC and high-affinity antibody secretion. Mechanistically, IL-2 induced early mTOR activity, expression of the transcriptional regulator IRF4, and metabolic changes in B cells required to form Blimp-1-expressing plasma cells. Thus, T cell help via IL-2 regulates an mTOR-AKT-Blimp-1 axis in activated B cells, providing insight into the mechanisms that determine EF versus GC fates and positioning IL-2 as an early switch controlling plasma cell versus GC B cell commitment.

Productions of Th2 cytokines, IL-4 and IL-10, were enhanced via the function of IL-2 from anti-CD3 antibody-stimulated mouse spleen cells treated with caffeic acid phenethyl ester

OBJECTIVES

Interleukin (IL)-2 production by mouse spleen cells stimulated with an anti-CD3 antibody is significantly enhanced by caffeic acid phenethyl ester (CAPE), a major constituent of Chinese propolis (CP). In this study, we evaluated the functional significance of IL-2 in CAPE-treated activated spleen cells.

METHODS

Mouse spleen cells were stimulated with an anti-CD3 monoclonal antibody in the presence of CAPE. Cytokine production was examined using an enzyme-linked immunosorbent assay (ELISA). Messenger RNA expression was examined via reverse transcription quantitative polymerase chain reaction (RT-PCR). IL-2 function was assessed using IL-2 and a neutralizing antibody. Spleen cell subsets were identified and characterized using flow cytometry.

RESULTS

CAPE treatment of anti-CD3 antibody-stimulated spleen cells reduced IFN-γ production, then enhanced IL-2 production, followed by enhancement of IL-4 and IL-10 production. The Th2 cytokine production enhancing effects of CAPE were completely abolished by addition of an anti-IL-2 neutralizing antibody. In the absence of CAPE, exogenously added IL-2 could enhance IL-4 production to a lesser degree, but did not stimulate IL-10 production, in stimulated spleen cells. Interestingly, CAPE significantly reduced the proportions of CD4+ and CD8+ cells, and increased those of CD4-CD8- cells among anti-CD3 stimulated spleen cells, in the presence or absence of anti-IL-2 neutralizing antibody treatment.

CONCLUSION

CAPE reduced IFN-γ production, then enhanced IL-4 and IL-10 production via the activity of specifically elevated IL-2 in stimulated spleen cells. CAPE exerted these effects in a CD4- CD8- cell specific manner.

Cutting Edge: Low-dose Recombinant IL-2 Treatment Prevents Autoantibody Responses in Systemic Lupus Erythematosus via Regulatory T Cell-independent Depletion of T Follicular Helper Cells

The expansion of T follicular helper (Tfh) cells correlates with disease progression in human and murine systemic lupus erythematosus (SLE). Unfortunately, there are no therapies to deplete Tfh cells. Importantly, low-dose rIL-2-based immunotherapy shows potent immunosuppressive effects in SLE patients and lupus-prone mice, primarily attributed to the expansion of regulatory T cells (Tregs). However, IL-2 can also inhibit Tfh cell differentiation. In this study, we investigate the potential of low-dose rIL-2 to deplete Tfh cells and prevent autoantibody responses in SLE. Our data demonstrate that low-dose rIL-2 efficiently depletes autoreactive Tfh cells and prevents autoantibody responses in lupus-prone mice. Importantly, this immunosuppressive effect was independent of the presence of Tregs. The therapeutic potential of eliminating Tfh cells was confirmed by selectively deleting Tfh cells in lupus-prone mice. Our findings demonstrate the critical role of Tfh cells in promoting autoantibody responses and unveil, (to our knowledge), a novel Treg-independent immunosuppressive function of IL-2 in SLE.

Armed with IL-2 based fusion protein improves CAR-T cell fitness and efficacy against solid tumors

Chimeric antigen receptor T (CAR-T) cell therapy is regarded as a potent immunotherapy and has made significant success in hematologic malignancies by eliciting antigen-specific immune responses. However, response rates of CAR-T cell therapy against solid tumors with immunosuppressive microenvironments remain limited. Co-engineering strategies are advancing methods to overcome immunosuppressive barriers and enhance antitumor responses. Here, we engineered an IL-2 mutein co-engineered CAR-T for the improvement of CAR-T cells against solid tumors and the efficient inhibition of solid tumors. We equipped the CAR-T cells with co-expressing both tumor antigen-targeted CAR and a mutated human interleukin-2 (IL-2m), conferring enhanced CAR-T cells fitness in vitro, reshaped immune-excluded TME, enhanced CAR-T infiltration in solid tumors, and improved tumor control without significant systemic toxicity. Overall, this subject demonstrates the universal CAR-T cells armed strategy for the development and optimization of CAR-T cells against solid tumors.

An Updated Review of Interleukin-2 Therapy in Cancer and Autoimmune Diseases

Interleukin-2 (IL-2) is a cytokine that acts in dual and paradoxical ways in the immunotherapy of cancers and autoimmune diseases. Numerous clinical trial studies have shown that the use of different doses of this cytokine in various autoimmune diseases, transplantations, and cancers has resulted in therapeutic success. However, side effects of varying severity have been observed in patients. In recent years, to prevent these side effects, IL-2 has been engineered to bind more specifically to its receptors on the cell surface, decreasing IL-2 toxicities in patients. In this review article, we focus on some recent clinical trial studies and analyze them to determine the appropriate dose of IL-2 drug with the least toxicities. In addition, we discuss the engineering performed on IL-2, which shows that engineered IL-2 increases the specificity function of IL-2 and decreases its adverse effects.

Pathogenesis and novel therapeutics of regulatory T cell subsets and interleukin-2 therapy in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a heterogeneous multisystem inflammatory disease with wide variability in clinical manifestations. Natural arising CD4+ regulatory T cells (Tregs) play a critical role in maintaining peripheral tolerance by suppressing inflammation and preventing autoimmune responses in SLE. Additionally, CD8+ regulatory T cells, type 1 regulatory T cells (Tr1), and B regulatory cells also have a less well-defined role in the pathogenesis of SLE. Elucidation of the roles of various Treg subsets dedicated to immune homeostasis will provide a novel therapeutic approach that governs immune tolerance for the remission of active lupus. Diminished interleukin (IL)-2 production is associated with a depleted Treg cell population, and its reversibility by IL-2 therapy provides important reasons for the treatment of lupus. This review focuses on the pathogenesis and new therapeutics of human Treg subsets and low-dose IL-2 therapy in clinical benefits with SLE.

Tumour-infiltrating B cells: immunological mechanisms, clinical impact and therapeutic opportunities

Although immunotherapy research to date has focused largely on T cells, there is mounting evidence that tumour-infiltrating B cells and plasma cells (collectively referred to as tumour-infiltrating B lymphocytes (TIL-Bs)) have a crucial, synergistic role in tumour control. In many cancers, TIL-Bs have demonstrated strong predictive and prognostic significance in the context of both standard treatments and immune checkpoint blockade, offering the prospect of new therapeutic opportunities that leverage their unique immunological properties. Drawing insights from autoimmunity, we review the molecular phenotypes, architectural contexts, antigen specificities, effector mechanisms and regulatory pathways relevant to TIL-Bs in human cancer. Although the field is young, the emerging picture is that TIL-Bs promote antitumour immunity through their unique mode of antigen presentation to T cells; their role in assembling and perpetuating immunologically 'hot' tumour microenvironments involving T cells, myeloid cells and natural killer cells; and their potential to combat immune editing and tumour heterogeneity through the easing of self-tolerance mechanisms. We end by discussing the most promising approaches to enhance TIL-B responses in concert with other immune cell subsets to extend the reach, potency and durability of cancer immunotherapy.

Enhanced production of IL-2 from anti-CD3 antibody-stimulated mouse spleen cells by artepillin C, a major component of Brazilian green propolis

OBJECTIVES

In this report, we attempt to clarify the immune modulatory effects of Brazilian green propolis (BGP) and its major component, artepillin C, on the cytokine production of anti-CD3 antibody-stimulated mouse spleen cells. We also estimate the physiological mechanism affecting artepillin C's upon the cells.

METHODS

Male C3H/HeN mouse spleen cells stimulated by antiCD3 monoclonal antibody were co-cultured with BGP, artepillin C, and HC030031, a transient receptor potential ankyrin 1 (TRPA1) Ca²⁺ channel antagonist. The synthesis of interferon (IFN)-γ, interleukin (IL)-6, IL-17, IL-4, IL-10, and IL-2 was assayed by enzyme-linked immunoassay. The expression of IL-2 mRNA and the protein product were examined by reverse transcription-quantitative polymerase chain reaction and Western blot analyses, respectively.

RESULTS

The production of IL-2 was markedly enhanced, while that of IL-4 and IL-10 was not significantly affected; by contrast, the production of IFN-γ, IL-6, and IL-17 was significantly reduced in the antibody-stimulated spleen cells treated with BGP at a non-cytostatic concentration. These effects were reproduced in the cells treated with artepillin C. The expression of IL-2 mRNA was unaffected; however, that of the protein was significantly enhanced in the artepillin C-treated cells compared to untreated control cells. The enhancement of protein expression and the production of IL-2 by artepillin C was significantly alleviated by adding HC030031.

CONCLUSIONS

Artepillin C is an important regulator of cytokine synthesis from activated spleen cells. The agent specifically augmented the expression of IL-2 via the Ca²⁺-permeable cation channel, TRPA1, at least in part, at the translational or secretion levels.