Anti-lipid IgG antibodies are produced in some mycobacterial infections and in certain autoimmune diseases [such as anti-phospholipid syndrome, systemic lupus erythematosus (SLE)]. However, few studies have addressed the B cell responses underlying the production of these immunoglobulins. Anti-lipid IgG antibodies are consistently found in a murine model resembling human lupus induced by chlorpromazine-stabilized non-bilayer phospholipid arrangements (NPA). NPA are transitory lipid associations found in the membranes of most cells; when NPA are stabilized they can become immunogenic and induce specific IgG antibodies, which appear to be involved in the development of the mouse model of lupus. Of note, anti-NPA antibodies are also detected in patients with SLE and leprosy. We used this model of lupus to investigate in vivo the cellular mechanisms that lead to the production of anti-lipid, class-switched IgG antibodies. In this murine lupus model, we found plasma cells (Gr1−, CD19−, CD138+) producing NPA-specific IgGs in the draining lymph nodes, the spleen, and the bone marrow. We also found a significant number of germinal center B cells (IgD−, CD19+, PNA+) specific for NPA in the draining lymph nodes and the spleen, and we identified in situ the presence of NPA in these germinal centers. By contrast, very few NPA-specific, extrafollicular reaction B cells (B220+, Blimp1+) were found. Moreover, when assessing the anti-NPA IgG antibodies produced during the experimental protocol, we found that the affinity of these antibodies progressively increased over time. Altogether, our data indicate that, in this murine model resembling human lupus, B cells produce anti-NPA IgG antibodies mainly via germinal centers.

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Systemic lupus erythematosus (SLE) is a chronic and multisystemic autoimmune disease characterized by deregulated innate and adaptive immune responses, which lead to the polyclonal activation of B cells and to a massive production of auto-antibodies that form immune complexes and cause tissue damage. SLE aetiology is not completely understood,

Systemic lupus erythematosus (SLE) is characterized by deregulated activation of T and B cells, autoantibody production, and consequent formation of immune complexes. Liposomes with nonbilayer phospholipid arrangements (NPA), induced by chlorpromazine, procainamide, or manganese, provoke a disease resembling human lupus when administered to mice. These mice produce anti-NPA IgM and IgG antibodies and exhibit an increased number of TLR-expressing spleen cells and a modified gene expression associated with TICAM1-dependent TLR-4 signaling (including IFNA1 and IFNA2) and complement activation. Additionally, they showed a diminished gene expression related to apoptosis and NK cell activation. We hypothesized that such gene expression may be affected by miRNAs and so miRNA expression was studied. Twelve deregulated miRNAs were found. Six of them were common to the three lupus-like models. Their validation by qRT-PCR and TaqMan probes, including miR-342-3p, revealed that miR-155-5p and miR-200a-3p expression was statistically significant. Currently described functions for these miRNAs in autoimmune diseases such as SLE reveal their participation in inflammation, interferon production, germinal center responses, and antibody maturation. Taking into account these findings, we propose miR-155-5p and miR-200a-3p, together with the anti-NPA antibodies, as key players in the murine lupus-like models and possible biomarkers of the human SLE.

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Liposomes are artificial models of cellular membranes that are used as delivery systems for genes, drugs and protein antigens. We have previously used them to study the antigenic properties of their phospholipids. Here, we used them to induce the production of IgG anti-non-bilayer phospholipid arrangements (NPAs) antibodies in mice; these antibodies cause cell lysis and trigger a lupus-like disease in mice. We studied the mechanisms that lead to the production of these antibodies, and provide evidence that NK1.1+, CD4+ T cells respond to NPA-bearing liposomes and deliver the help required for specific B cell activation and antibody class-switching to IgG. We found increased numbers of IL-4-producing NK1.1+, CD4+ T cells in the secondary lymphoid organs of mice administered with NPAs, and these cells also expressed CD40L, which is required for B cell activation. Additionally, we isolated and purified NK1.1+, CD4+ T cells from spleens and determined that they over-expressed 40 genes, which are key players in inflammatory processes and B cell stimulation and have TRAF6 and UNC39B1 as key nodes in their network. These results show that liposomes are membrane models that can be used to analyze the immunogenicity of lipids.

Chagas disease is a parasitic disease caused by Trypanosoma cruzi it is endemic in Latin America, where is a major health problem since it affects 8–10 million people, causes 50,000 deaths per year and about 25% of the population is at risk of acquiring the disease. It remains practically incurable, mainly because of the limited interest in developing new drugs and because the drugs available for its treatment, Benznidazole (Bz) and Nifurtimox (Nx) are inefficient to cure patients. The acute phase of the disease appears shortly after infection, the chronic phase appears after a silent asymptomatic period that may last several years. During the chronic phase, the heart, esophagus, colon and PNS are irreversibly affected, patients usually die from heart failure. The chronic phase may be established by the evasion of the immune response by the parasite, secondly because Bz and Nx generate free radicals that can affect the cells of the immune system (CIS) which could favour the chronic phase. In our research group, we design and synthesized the benzyl ester of Npropyl oxamic (NPOxB) that is an effective inhibitor of the alpha-hydroxy acid dehydrogenase II enzyme, which is a specific enzyme in the glycolytic pathway of the parasite. In this work we treated with NPOxB or Bz infected mice with NINOA or INC5 strains, we evaluate the parasitaemia, the macrophages, B, T, plasma and dendritic cells. The NPOx-B decreased more the parasitaemia of both T. cruzi strains than the Bz. The mice infected and treated with Bz showed a decrease in B, T and plasma cells compared to the infected mice treated with NPOxB. So NPOxB is more effective in decrease the parasitaemia and lacks the toxicity of Bz, it doesn’t affect in CIS, the cure of the disease can be achieved more efficiently.

Anti-lipid IgG antibodies can participate in the physiopathology of some autoimmune diseases. In our research group, we developed a mouse model of Lupus by the administration of liposomes bearing non-bilayer phospholipid arrangements NPA induced by some drugs like chloropromazine CPZ. The mice of this model produce anti-NPA IgG antibodies; these antibodies are mainly formed via germinal center GC. However, the cells that participate in a GC reaction against lipidic antigens are unknown; therefore, we study these cells in the mouse model of Lupus induced by NPA and compared them with a GC reaction against ovalbumin OVA, because the cells that participate in a GC reaction against protein antigens are well known. We studied germinal center B cells, plasma cells, dendritic cells, follicular dendritic cells FDC, T follicular helper cells TFH, T follicular regulatory cells TFR and macrophages from the groups administered with OVA or NPA and compared them with mice without administration. Then we extracted the spleen and the mesenteric lymph nodes and perform flow cytometry and H&E staining at days 5, 10, 15 and 30 postadministration. Histologically, germinal centers were found in both groups at day 5. The mice administered with NPA, present an increase of germinal center B cells 15 days post-administration and a bigger size of the secondary lymphoid organs, the mice administrated with OVA present an increase of these cells and bigger lymph organs at day 10. The higher percentage of plasma cells was found 30 days after the administration of OVA; while dendritic cells and TFH cells presented similar percentages in both groups at all times. For both antigens, the FDC increase at day 5 and 15, the macrophages from day 10 to 15 and the TFR cells increase at day 15.