Role of B-1 cells in the immune response against an antigen encapsulated into phosphatidylcholine-containing liposomes

Post-transcriptional (re)programming of B lymphocyte development: From bench to bedside?

Hematopoiesis, a process which generates blood and immune cells, changes significantly during mammalian development. Definitive hematopoiesis is marked by the emergence of long-term hematopoietic stem cells (HSCs). Here, we will focus on the post-transcriptional differences between fetal liver (FL) and adult bone marrow (ABM) HSCs. It remains unclear how or why exactly FL HSCs transition to ABM HSCs, but we aim to leverage their differences to revive an old idea: in utero HSC transplantation. Unexpectedly, the expression of certain RNA-binding proteins (RBPs) play an important role in HSC specification, and can be employed to convert or reprogram adult HSCs back to a fetal-like state. Among other features, FL HSCs have a broad differentiation capacity that includes the ability to regenerate both conventional B and T cells, as well as innate-like or unconventional lymphocytes such as B-1a and marginal zone B (MzB) cells. This chapter will focus on RNA binding proteins, namely LIN28B and IGF2BP3, that are expressed during fetal life and how they promote B-1a cell development. Furthermore, this chapter considers a potential clinical application of synthetic co-expression of LIN28B and IGF2BP3 in HSCs.

B-1 cells in immunotoxicology: Mechanisms underlying their response to chemicals and particles

Since their discovery nearly 40 years ago, B-1 cells have continued to challenge the boundaries between innate and adaptive immunity, as well as myeloid and lymphoid functions. This B-cell subset ensures early immunity in neonates before the development of conventional B (B-2) cells and respond to immune injuries throughout life. B-1 cells are multifaceted and serve as natural- and induced-antibody-producing cells, phagocytic cells, antigen-presenting cells, and anti-/pro-inflammatory cytokine-releasing cells. This review retraces the origin of B-1 cells and their different roles in homeostatic and infectious conditions before focusing on pollutants comprising contact-sensitivity-inducing chemicals, endocrine disruptors, aryl hydrocarbon receptor (AHR) ligands, and reactive particles.

Review: Liposomes in the prophylaxis and treatment of infectious diseases

Infectious diseases remain as one of the major burdens among health communities as well as in the general public despite the advances in prevention and treatment. Although vaccination and vector eliminations have greatly prevented the transmission of these diseases, the effectiveness of these strategies is no longer guaranteed as new challenges such as drug resistance and toxicity as well as the missing effective therapeutics arise. Hence, the development of new tools to manage these challenges is anticipated, in which nano technology using liposomes as effective nanostructure is highly considered. In this review, we concentrate on the advantages of liposomes in the drug delivery system and the development of vaccine in the treatment of three major infectious diseases; tuberculosis (TB), malaria and HIV.

Recent advances in mRNA-LNP therapeutics: immunological and pharmacological aspects

In the last decade, the development of messenger RNA (mRNA) therapeutics by lipid nanoparticles (LNP) leads to facilitate clinical trial recruitment, which improves the efficacy of treatment modality to a large extent. Although mRNA-LNP vaccine platforms for the COVID-19 pandemic demonstrated high efficiency, safety and adverse effects challenges due to the uncontrolled immune responses and inappropriate pharmacological interventions could limit this tremendous efficacy. The current study reveals the interplay of immune responses with LNP compositions and characterization and clarifies the interaction of mRNA-LNP therapeutics with dendritic, macrophages, neutrophile cells, and complement. Then, pharmacological profiles for mRNA-LNP delivery, including pharmacokinetics and cellular trafficking, were discussed in detail in cancer types and infectious diseases. This review study opens a new and vital landscape to improve multidisciplinary therapeutics on mRNA-LNP through modulation of immunopharmacological responses in clinical trials.

Ancient Evolutionary Origin and Properties of Universally Produced Natural Exosomes Contribute to Their Therapeutic Superiority Compared to Artificial Nanoparticles

Extracellular vesicles (EVs), such as exosomes, are newly recognized fundamental, universally produced natural nanoparticles of life that are seemingly involved in all biologic processes and clinical diseases. Due to their universal involvements, understanding the nature and also the potential therapeutic uses of these nanovesicles requires innovative experimental approaches in virtually every field. Of the EV group, exosome nanovesicles and larger companion micro vesicles can mediate completely new biologic and clinical processes dependent on the intercellular transfer of proteins and most importantly selected RNAs, particularly miRNAs between donor and targeted cells to elicit epigenetic alterations inducing functional cellular changes. These recipient acceptor cells are nearby (paracrine transfers) or far away after distribution via the circulation (endocrine transfers). The major properties of such vesicles seem to have been conserved over eons, suggesting that they may have ancient evolutionary origins arising perhaps even before cells in the primordial soup from which life evolved. Their potential ancient evolutionary attributes may be responsible for the ability of some modern-day exosomes to withstand unusually harsh conditions, perhaps due to unique membrane lipid compositions. This is exemplified by ability of the maternal milk exosomes to survive passing the neonatal acid/enzyme rich stomach. It is postulated that this resistance also applies to their durable presence in phagolysosomes, thus suggesting a unique intracellular release of their contained miRNAs. A major discussed issue is the generally poorly realized superiority of these naturally evolved nanovesicles for therapies when compared to human-engineered artificial nanoparticles, e.g., for the treatment of diseases like cancers.

Interrogation of Folic Acid-Functionalized Nanomedicines: The Regulatory Roles of Plasma Proteins Reexamined

Folic acid (FA) has been extensively exploited to facilitate targeted delivery of nanomedicines by recognizing the folate receptor-α (FR-α) overexpressed in many human cancers. Unfortunately, none have been approved for clinical use yet. Here we reveal that FA functionalization induces heavy natural IgM absorption on the liposomal surface, depriving FA of receptor recognition and accelerating complement activation in vivo. FA functionalization does not enhance distribution of liposomes in FR-α-overexpressed tumors in comparison to plain liposomes (without FA), but leads to aggravated capture of liposomes by macrophages in the tumor, liver, and spleen. In addition, FA-functionalized polymeric nanoparticles are also vulnerable to natural IgM absorption. This work highlights the pivotal roles of natural IgM in regulating in vivo delivery of FA-functionalized nanomedicines. Due to the prevalent association of immune disorders and varying levels of immunoglobulins with cancer patients, extraordinary cautiousness is urged for clinical translation of FA-enabled targeted delivery systems.

ACTH4-10 protects the ADR-injured podocytes by stimulating B lymphocytes to secrete interleukin-10

OBJECTIVES

In the present study, we aimed to assess whether adrenocorticotropic hormone (ACTH) could protect the podocytes from adriamycin (ADR)-induced injury by stimulating B lymphocytes to secrete the associated cytokines.

METHODS

Proliferation assay was used to assess the proliferation and activity of podocytes. Enzyme-linked immunosorbent assay was used to examine the secretion of IL-10 and IL-4. TUNEL apoptosis detection kit was used to detect the apoptosis of podocytes. Real-time PCR and Western blotting analysis were used to examine the expressions of nephrin and podocin at the mRNA and protein levels.

RESULTS

Compared with the normal control group, the podocyte proliferation of ADR group was significantly inhibited. However, compared with the ADR group, the podocyte proliferation of the supernatant (1 µg/L, 10 µg/L or 100 µg/L ACTH_4-10) + ADR groups was generally increased, and the pro-proliferative effect of the supernatant containing 10 µg/L ACTH_4-10 was the highest. Moreover, we found that after B lymphocytes were intervened by 10 µg/L ACTH4-10, the IL-10 level in the cell supernatant was significantly elevated (p < 0.05). When anti-IL-10R was added, the podocyte proliferation of the supernatant (10 µg/L ACTH_4-10) + ADR group was significantly inhibited. Furthermore, the supernatant of B cells stimulated with 10 µg/L ACTH_4-10 could better decrease the apoptosis rate of injured podocytes and increase the expressions of nephrin and podocin at the mRNA and protein levels by elevating the secretion of IL-10.

CONCLUSION

Compared with ACTH_4-10, the supernatant of B cells stimulated with ACTH_4-10 could better protect the podocytes from ADR-induced injury by elevating the secretion of IL-10.

Homeostasis and regulation of autoreactive B cells

In contrast to the previous belief that autoreactive B cells are eliminated from the normal repertoire of B cells, many autoreactive B cells actually escape clonal deletion and develop into mature B cells. These autoreactive B cells in healthy individuals perform some beneficial functions in the host and are homeostatically regulated by regulatory T and B cells or other mechanisms to prevent autoimmune diseases. Autoreactive B-1 cells constitutively produce polyreactive natural antibodies for tissue homeostasis. Recently, autoreactive follicular B cells were reported to participate actively in the germinal center reaction. Furthermore, the selection and usefulness of autoreactive marginal zone (MZ) B cells found in autoimmune diseases are not well understood, although the repertoire of MZ B-cell receptors (BCRs) is presumed to be biased to detect bacterial antigens. In this review, we discuss the autoreactive B-cell populations among all three major B-cell subsets and their regulation in immune responses and diseases.

B-CD8+ T Cell Interactions in the Anti-Idiotypic Response against a Self-Antibody

P3 is a murine, germline, IgM mAb that recognizes N-glycolylated gangliosides and other self-antigens. This antibody is able to induce an anti-idiotypic IgG response and B-T idiotypic cascade, even in the absence of any adjuvant or carrier protein. P3 mAb immunization induces the expression of activation markers in a significant percentage of B-1a cells in vivo. Interestingly, transfer of both B-1a and B-2 to BALB/Xid mice was required to recover anti-P3 IgG response in this model. In fact, P3 mAb activated B-2 cells, in vitro, inducing secretion of IFN-γ and IL-4, although this activation was not detected ex vivo. Interestingly, naïve CD8+ T cells increased the expression of activation markers and IFN-γ secretion in the presence of B-1a cells isolated from P3 mAb-immunized mice, even without in vitro restimulation. In contrast, B-2 cells were able to stimulate CD8+ T cells only if P3 was added in vitro. Using bioinformatics, a MHC class I-binding peptide from P3 VH region was identified. P3 mAb was able to induce a specific CTL response in vivo against cells presenting this peptide. Both humoral and CTL anti-idiotypic responses could be mechanisms to protect against the self-reactive antibody, contributing to keeping the tolerance to self-antigens.

Novel Adjuvant Based on the Pore-Forming Protein Sticholysin II Encapsulated into Liposomes Effectively Enhances the Antigen-Specific CTL-Mediated Immune Response

Vaccine strategies to enhance CD8⁺ CTL responses remain a current challenge because they should overcome the plasmatic and endosomal membranes for favoring exogenous Ag access to the cytosol of APCs. As a way to avoid this hurdle, sticholysin (St) II, a pore-forming protein from the Caribbean Sea anemone Stichodactyla helianthus, was encapsulated with OVA into liposomes (Lp/OVA/StII) to assess their efficacy to induce a CTL response. OVA-specific CD8⁺ T cells transferred to mice immunized with Lp/OVA/StII experienced a greater expansion than when the recipients were injected with the vesicles without St, mostly exhibiting a memory phenotype. Consequently, Lp/OVA/StII induced a more potent effector function, as shown by CTLs, in vivo assays. Furthermore, treatment of E.G7-OVA tumor-bearing mice with Lp/OVA/StII significantly reduced tumor growth being more noticeable in the preventive assay. The contribution of CD4⁺ and CD8⁺ T cells to CTL and antitumor activity, respectively, was elucidated. Interestingly, the irreversibly inactive variant of the StI mutant StI W111C, encapsulated with OVA into Lp, elicited a similar OVA-specific CTL response to that observed with Lp/OVA/StII or vesicles encapsulating recombinant StI or the reversibly inactive StI W111C dimer. These findings suggest the relative independence between StII pore-forming activity and its immunomodulatory properties. In addition, StII-induced in vitro maturation of dendritic cells might be supporting these properties. These results are the first evidence, to our knowledge, that StII, a pore-forming protein from a marine eukaryotic organism, encapsulated into Lp functions as an adjuvant to induce a robust specific CTL response.

Phosphocholine-Specific Antibodies Improve T-Dependent Antibody Responses against OVA Encapsulated into Phosphatidylcholine-Containing Liposomes

Liposomes containing phosphatidylcholine have been widely used as adjuvants. Recently, we demonstrated that B-1 cells produce dipalmitoyl-phosphatidylcholine (DPPC)-specific IgM upon immunization of BALB/c mice with DPPC-liposomes encapsulating ovalbumin (OVA). Although this preparation enhanced the OVA-specific humoral response, the contribution of anti-DPPC antibodies to this effect was unclear. Here, we demonstrate that these antibodies are secreted by B-1 cells independently of the presence of OVA in the formulation. We also confirm that these antibodies are specific for phosphocholine. The anti-OVA humoral response was partially restored in B-1 cells-deficient BALB/xid mice by immunization with the liposomes opsonized with the serum total immunoglobulin (Ig) fraction containing anti-phosphocholine antibodies, generated in wild-type animals. This result could be related to the increased phagocytosis by peritoneal macrophages of the particles opsonized with the serum total Ig or IgM fractions, both containing anti-phosphocholine antibodies. In conclusion, in the present work, it has been demonstrated that phosphocholine-specific antibodies improve T-dependent antibody responses against OVA carried by DPPC-liposomes.

Integration of Quercetin-Iron Complexes into Phosphatidylcholine or Phosphatidylethanolamine Liposomes

It is well known that flavonoids can chelate transition metals. Flavonoid-metal complexes exhibit a high antioxidative and therapeutic potential. However, the complexes are frequently hydrophobic ones and low soluble in water, which restricts their medical applications. Integration of these complexes into liposomes may increase their bioavailability and therapeutic effect. Here, we studied the interaction of quercetin-iron complexes with dimyristoylphosphatidylcholine (DMPC) or palmitoyl-oleoyl phosphatidylethanolamine (POPE) multilamellar liposomes. Differential scanning calorimetry (DSC) and freeze-fracture electron microscopy revealed that quercetin-iron complexes did not interact with liposomes. Quercetin however could penetrate lipid bilayers, when added to liposomes at a temperature above lipid melting. Iron cations added later penetrated into the lipid bilayers and produced complexes with quercetin in the liposomes. The quercetin-iron entry in POPE liposomes was improved when the suspension was heated above the temperature of the bilayer-hexagonal HII phase transition of the lipid. The approach proposed facilitates the integration of quercetin-iron complexes into liposomes and may promote their use in medicine.

The PGE2/IL-10 Axis Determines Susceptibility of B-1 Cell-Derived Phagocytes (B-1CDP) to Leishmania major Infection

B-1 cells can be differentiated from B-2 cells because they are predominantly located in the peritoneal and pleural cavities and have distinct phenotypic patterns and activation properties. A mononuclear phagocyte derived from B-1 cells (B-1CDP) has been described. As the B-1CDP cells migrate to inflammatory/infectious sites and exhibit phagocytic capacity, the microbicidal ability of these cells was investigated using the Leishmania major infection model in vitro. The data obtained in this study demonstrate that B-1CDP cells are more susceptible to infection than peritoneal macrophages, since B-1CDP cells have a higher number of intracellular amastigotes forms and consequently release a larger number of promastigotes. Exacerbated infection by L. major required lipid bodies/PGE₂ and IL-10 by B-1CDP cells. Both infection and the production of IL-10 were decreased when PGE₂ production was blocked by NSAIDs. The involvement of IL-10 in this mechanism was confirmed, since B-1CDP cells from IL-10 KO mice are more competent to control L. major infection than cells from wild type mice. These findings further characterize the B-1CDP cells as an important mononuclear phagocyte that plays a previously unrecognized role in host responses to L. major infection, most likely via PGE₂-driven production of IL-10.

High fat diet deviates PtC-specific B1 B cell phagocytosis in obese mice

Phagocytosis had been attributed predominantly to "professional" phagocytes such as macrophages, which play critical roles in adipose tissue inflammation. However, recently, macrophage-like phagocytic activity has been reported in B1 B lymphocytes. Intrigued by the long-established correlation between high fat diet (HFD)-induced obesity and immune dysfunction, we investigated how HFD affects B1 B cell phagocytosis. A significant number of B1 B cells recognize phosphatidylcholine (PtC), a common phospholipid component of cell membrane. We report here that unlike macrophages, B1 B cells have a unique PtC-specific phagocytic function. In the presence of both PtC-coated and non-PtC control fluorescent nano-particles, B1 B cells from healthy lean mice selectively engulfed PtC-coated beads, whereas B1 B cells from HFD-fed obese mice non-discriminately phagocytosed both PtC-coated and control beads. Morphologically, B1 B cells from obese mice resembled macrophages, displaying enlarged cytosol and engulfed more beads. Our study suggests for the first time that HFD can affect B1 B cell phagocytosis, substantiating the link of HFD-induced obesity and immune deviation.