Podocyte-specific knockout of the neonatal Fc receptor (FcRn) results in differential protection depending on the model of glomerulonephritis

Podocytes have been proposed to be antigen presenting cells (APCs). In traditional APCs, the neonatal Fc receptor (FcRn) is required for antigen presentation and global knockout of FcRn protects against glomerulonephritis. Since podocytes express FcRn, we sought to determine whether the absence of podocyte FcRn ameliorates immune-mediated disease. We examined MHCII and costimulatory markers expression in cultured wild type (WT) and FcRn knockout (KO) podocytes. Interferon gamma (IFNγ) induced MHCII expression in both WT and KO podocytes but did not change CD80 expression. Neither WT nor KO expressed CD86 or inducible costimulatory ligand (ICOSL) at baseline or with IFNγ. Using an antigen presentation assay, WT podocytes but not KO treated with immune complexes induced a modest increase in IL-2. Induction of the anti-glomerular basement membrane (anti-GBM) model resulted in a significant decrease in glomerular crescents in podocyte-specific FcRn knockout mouse (podFcRn KO) versus controls but the overall percentage of crescents was low. To examine the effects of the podocyte-specific FcRn knockout in a model with a longer autologous phase, we used the nephrotoxic serum nephritis (NTS) model. We found that the podFcRn KO mice had significantly reduced crescent formation and glomerulosclerosis compared to control mice. This study demonstrates that lack of podocyte FcRn is protective in immune mediated kidney disease that is dependent on an autologous phase. This study also highlights the difference between the anti-GBM model and NTS model of disease.

Download Full-text

Podocyte-specific knockout of the neonatal Fc receptor (FcRn) results in differential protection depending on the model of immune-mediated kidney disease

10.1101/2020.03.02.972851 ◽

2020 ◽

Author(s):

James Dylewski ◽

Pantipa Tonsawan ◽

Gabriela Garcia ◽

Linda Lewis ◽

Judith Blaine

Keyword(s):

Kidney Disease ◽

Antigen Presentation ◽

Fc Receptor ◽

Differential Protection ◽

Neonatal Fc Receptor ◽

Crescent Formation ◽

Immune Mediated ◽

The Difference ◽

Antigen Presenting ◽

Mhcii Expression

AbstractPodocytes have been proposed to be antigen presenting cells (APCs). In traditional APCs, the neonatal Fc receptor (FcRn) is required for antigen presentation and global knockout of FcRn protects against immune-mediated kidney disease. Since podocytes express FcRn, we sought to determine whether the absence of podocyte FcRn ameliorates immune-mediated disease. We examined MHCII and costimulatory markers expression in cultured wild type (WT) and FcRn knockout (KO) podocytes. Interferon gamma (IFNγ) induced MHCII expression in both WT and KO podocytes but did not change CD80 expression. Neither WT nor KO expressed CD86 or inducible costimulatory ligand (ICOSL) at baseline or with IFNγ. Using an antigen presentation assay, WT podocytes but not KO treated with immune complexes induced a modest increase in IL-2. Induction of the anti-glomerular basement membrane (anti-GBM) model resulted in a significant decrease in glomerular crescents in podocyte-specific FcRn knockout mouse (podFcRn KO) versus controls but the overall percentage of crescents was low. To examine the effects of the podocyte-specific FcRn knockout in a model with a longer autologous phase, we used the nephrotoxic serum nephritis (NTS) model. We found that the podFcRn KO mice had significantly reduced crescent formation and glomerulosclerosis compared to control mice. This study demonstrates that lack of podocyte FcRn is protective in immune mediated kidney disease that is dependent on an autologous phase. This study also highlights the difference between the anti-GBM model and NTS model of disease.

Download Full-text

Knockout of the neonatal Fc receptor in cultured podocytes alters IL-6 signaling and the actin cytoskeleton

AJP Cell Physiology ◽

10.1152/ajpcell.00235.2019 ◽

2019 ◽

Vol 317 (5) ◽

pp. C1048-C1060 ◽

Cited By ~ 2

Author(s):

Pantipa Tonsawan ◽

James Dylewski ◽

Linda Lewis ◽

Judith Blaine

Keyword(s):

Immune Complexes ◽

Fc Receptor ◽

Actin Dynamics ◽

Minimal Amount ◽

Neonatal Fc Receptor ◽

Scratch Assay ◽

Immune Mediated ◽

Actin Structure ◽

Robust Response

The neonatal Fc receptor (FcRn) has been shown to be required for antigen presentation in dendritic cells, and global knockout of FcRn attenuates immune-mediated kidney disease. Podocytes express interleukin-6 (IL-6) receptor and produce IL-6 under proinflammatory conditions. Here we examined the role of FcRn in the IL-6-mediated inflammatory response in podocytes. We examined IL-6 production by ELISA and expression by qPCR in wild type (WT) and FcRn knockout (KO) podocytes after treatment with proinflammatory stimuli as well as IL-6-mediated signaling via the JAK/STAT pathway. We also examined podocyte motility in cultured WT and KO podocytes after a proinflammatory challenge. We found that FcRn KO podocytes produced minimal amount of IL-6 after treatment with albumin, IgG, or immune complexes whereas WT podocytes had a robust response. FcRn KO podocytes also had minimal expression of IL-6 compared with WT. By Western blotting, there was significantly less phosphorylated STAT3 in KO podocytes after treatment with IFNγ or immune complexes. In a scratch assay, FcRn KO podocytes showed increased motility comparted KO, suggesting a defect in actin dynamics. Cultured FcRn KO podocytes also demonstrated abnormal stress fibers compared with WT and the defect could be rescued by IL-6 treatment. This study shows that in podocytes, FcRn modulates the IL-6 mediated response to proinflammatory stimuli and regulates podocytes actin structure, motility and synaptopodin expression.

Download Full-text

Oral Fc-Coupled Preproinsulin Achieves Systemic and Thymic Delivery Through the Neonatal Fc Receptor and Partially Delays Autoimmune Diabetes

Frontiers in Immunology ◽

10.3389/fimmu.2021.616215 ◽

2021 ◽

Vol 12 ◽

Author(s):

Noémie Corcos ◽

Slobodan Culina ◽

Claire Deligne ◽

Cassandra Lavaud ◽

Sylvaine You ◽

...

Keyword(s):

Diabetes Prevention ◽

Autoimmune Diabetes ◽

Nod Mice ◽

Cell Receptor ◽

Fc Receptor ◽

Antigen Delivery ◽

Dependent Manner ◽

Neonatal Fc Receptor ◽

Central Tolerance ◽

Antigen Presenting

Tolerogenic vaccinations using beta-cell antigens are attractive for type 1 diabetes prevention, but clinical trials have been disappointing. This is probably due to the late timing of intervention, when multiple auto-antibodies are already present. We therefore devised a strategy to introduce the initiating antigen preproinsulin (PPI) during neonatal life, when autoimmunity is still silent and central tolerance mechanisms, which remain therapeutically unexploited, are more active. This strategy employs an oral administration of PPI-Fc, i.e. PPI fused with an IgG Fc to bind the intestinal neonatal Fc receptor (FcRn) that physiologically delivers maternal antibodies to the offspring during breastfeeding. Neonatal oral PPI-Fc vaccination did not prevent diabetes development in PPI T-cell receptor-transgenic G9C8.NOD mice. However, PPI-Fc was efficiently transferred through the intestinal epithelium in an Fc- and FcRn-dependent manner, was taken up by antigen presenting cells, and reached the spleen and thymus. Although not statistically significant, neonatal oral PPI-Fc vaccination delayed diabetes onset in polyclonal Ins2-/-.NOD mice that spontaneously develop accelerated diabetes. Thus, this strategy shows promise in terms of systemic and thymic antigen delivery via the intestinal FcRn pathway, but the current PPI-Fc formulation/regimen requires further improvements to achieve diabetes prevention.

Download Full-text

Expression of the Neonatal Fc Receptor FcRn Is Not Required for the Amelioration of Murine ITP by IVIg or a Monoclonal Antibody

Blood ◽

10.1182/blood.v116.21.2529.2529 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2529-2529

Author(s):

Andrew R. Crow ◽

Sara J Suppa ◽

Alan H Lazarus

Keyword(s):

Body Weight ◽

Immune Thrombocytopenia ◽

Conflicts Of Interest ◽

Fc Receptor ◽

High Dose ◽

Wild Type ◽

Neonatal Fc Receptor ◽

Antibody Treatment ◽

Deficient Mice ◽

Cd44 Antibody

Abstract Abstract 2529 There are several theories as to the mechanism of intravenous immunoglobulin (IVIg) in the treatment of autoimmune diseases such as immune thrombocytopenia (ITP). One prominent theory involves accelerated pathogenic autoantibody clearance by saturation of the neonatal Fc Receptor (FcRn). FcRn is an IgG receptor, and FcRn within endosomes binds endocytosed IgG and diverts IgG from degradation. In the treatment of ITP, it has been theorized that high concentrations of IVIg saturate FcRn, reducing the ability of the pathogenic anti-platelet antibodies to bind FcRn, increasing their catabolism, and thus rapidly decreasing their serum concentration which results in a decrease in their ability to induce platelet clearance. Mice lacking FcRn have only 20–30% of the level of endogenous IgG as compared with wild-type mice and have an accelerated clearance rate of both endogenous and injected IgG. We have utilized these mice in a murine model of ITP to help understand the role, if any, that FcRn plays in IVIg's therapeutic activity. Both IVIg (2 g/kg body weight) and monoclonal antibodies to CD44 (2 mg/kg body weight; please see submitted abstract ID# 29504, “Amelioration of murine immune thrombocytopenia by CD44 antibodies: a potential therapy for ITP?”) successfully ameliorate murine ITP. To definitively determine if FcRn is required for the acute amelioration of ITP by these two therapeutics, we employed FcRn deficient mice in the murine ITP model. Here, we demonstrate that FcRn deficient mice (B6.129X1-Fcgrttm1Dcr/DcrJ) injected with an anti-platelet antibody exhibit a slightly more profound degree of thrombocytopenia than wild-type mice. FcRn deficient mice treated with IVIg or the anti-CD44 antibody KM114 (at a 3 log fold lower dosage than IVIg) were protected from ITP to the same extent as wild-type mice. FcRn has an absolute requirement for the protein β2 microglobulin (β2M) to be functionally expressed. Specifically, β2M deficient mice do not possess functional FcRn and also show low endogenous IgG levels and increased clearance of IgG. To verify and substantiate the results found with FcRn deficient mice, we next employed β2M deficient mice in the murine ITP model and found that β2M deficient mice (B6.129P2-B2mtm1Unc/J) treated with IVIg or KM114 were also protected from ITP to the same extent as wild-type mice. These data suggest that for both high dose IVIg as well as low dose monoclonal CD44 antibody treatment in an acute ITP model, FcRn expression is dispensable. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

Presentation of ovalbumin internalized via the immunoglobulin-A Fc receptor is enhanced through Fc receptor γ-chain signaling

Blood ◽

10.1182/blood.v97.1.205 ◽

2001 ◽

Vol 97 (1) ◽

pp. 205-213 ◽

Cited By ~ 40

Author(s):

Li Shen ◽

Marjolein van Egmond ◽

Karyn Siemasko ◽

Hong Gao ◽

Terri Wade ◽

...

Keyword(s):

B Cell ◽

Antigen Presentation ◽

Antigen Processing ◽

Immunoglobulin A ◽

Fc Receptor ◽

Wild Type ◽

Endocytic Compartment ◽

Efficient Processing ◽

Activation Motif

Abstract The mechanism of enhanced presentation of ovalbumin (OVA) internalized as immunoglobulin A (IgA)–OVA via the IgA Fc receptor (FcαR) was analyzed by focusing on the role of the FcαR-associated γ chain. Comparison of B-cell transfectants expressing FcαR plus wild-type (WT) γ chain or γ chain in which the immunoreceptor tyrosine-based activation motif (ITAM) was altered by tyrosine mutation or substitution with the ITAM of FcγRIIA showed that signaling-competent ITAM was not required for endocytosis of IgA-OVA. However, antigen presentation was impaired by ITAM changes. Signaling-competent γ-chain ITAM appeared necessary for transport of ligated FcαR to a lamp-1+ late endocytic compartment for remodeling and/or activation of that compartment and also for efficient degradation of IgA complexes. Moreover, FcαR ligation also activated efficient processing of nonreceptor-targeted antigen. The results suggest that γ-chain signaling activates the antigen processing compartment.

Download Full-text

Effect of cold nerve allograft preservation on antigen presentation and rejection

Journal of Neurosurgery ◽

10.3171/2010.5.jns10111 ◽

2011 ◽

Vol 114 (1) ◽

pp. 256-262 ◽

Cited By ~ 10

Author(s):

Wilson Z. Ray ◽

Santosh S. Kale ◽

Rahul Kasukurthi ◽

Esther M. Papp ◽

Philip J. Johnson ◽

...

Keyword(s):

Antigen Presentation ◽

Nerve Regeneration ◽

Antigen Presenting Cells ◽

Significant Degree ◽

Relative Role ◽

Wild Type ◽

Indirect Pathway ◽

Cold Preservation ◽

Direct Pathway ◽

Antigen Presenting

Object Nerve allotransplantation provides a temporary scaffold for host nerve regeneration and allows for the reconstruction of significant segmental nerve injuries. The need for systemic immunosuppression, however, limits the current clinical utilization of nerve allografts, although this need is reduced by the practice of cold nerve allograft preservation. Activation of T cells in response to alloantigen presentation occurs in the context of donor antigen presenting cells (direct pathway) or host antigen-presenting cells (indirect pathway). The relative role of each pathway in eliciting an alloimmune response and its potential for rejection of the nerve allograft model has not previously been investigated. The objective of this investigation was to study the effect of progressive periods of cold nerve allograft preservation on antigen presentation and the alloimmune response. Methods The authors used wild type C57Bl/6 (B6), BALB/c, and major histocompatibility Class II–deficient (MHC−/−) C57Bl/6 mice as both nerve allograft recipients and donors. A nonvascularized nerve allograft was used to reconstruct a 1-cm sciatic nerve gap. Progressive cold preservation of donor nerve allografts was used. Quantitative assessment was made after 3 weeks using nerve histomorphometry. Results The donor-recipient combination lacking a functional direct pathway (BALB/c host with MHC−/− graft) rejected nerve allografts as vigorously as wild-type animals. Without an intact indirect pathway (MHC−/− host with BALB/c graft), axonal regeneration was improved (p < 0.052). One week of cold allograft preservation did not improve regeneration to any significant degree in any of the donor-recipient combinations. Four weeks of cold preservation did improve regeneration significantly (p < 0.05) for all combinations compared with wild-type animals without pretreatment. However, only in the presence of an intact indirect pathway (no direct pathway) did 4 weeks of cold preservation improve regeneration significantly compared with 1 week and no preservation in the same donorrecipient combination. Conclusions The indirect pathway may be the predominant route of antigen presentation in the unmodified host response to the nerve allograft. Prolonged duration of cold nerve allograft preservation is required to significantly attenuate the rejection response. Cold preservation for 4 weeks improves nerve regeneration with a significant effect on indirect allorecognition.

Download Full-text

Hormonally controlled ILC antigen presentation potential is reduced during pregnancy

Reproduction ◽

10.1530/rep-19-0554 ◽

2020 ◽

Vol 160 (1) ◽

pp. 155-169

Author(s):

Rebekka Einenkel ◽

Jens Ehrhardt ◽

Kristin Hartmann ◽

Diana Krüger ◽

Damián Oscar Muzzio ◽

...

Keyword(s):

Antigen Presentation ◽

Normal Pregnancy ◽

Lymphoid Cells ◽

Related Factors ◽

Pregnant Mice ◽

Uterine Environment ◽

Antigen Presenting ◽

Murine Pregnancy ◽

Mhcii Expression

Strategically located in mucosal barriers, innate lymphoid cells (ILCs) are relevant in local containment and tolerance of commensal microflora. ILCs have been recently described at the fetomaternal interface, where the development of a semi-allogeneic fetus can only succeed in a well-controlled immune environment. We postulate that ILCs adapt their antigen presentation capacity to protect pregnancy from excessive immune responses. Human ILCs were studied in deciduae of term pregnancies, peripheral blood and in in vitro generated ILCs. Fresh isolated lymphocytes or cells treated with pregnancy-related factors were investigated. The fetal antigen rejection-based CBA/J × DBA/2J mouse model (poor outcome pregnant mice; POPM) was used to characterize ILC antigen presentation potential in normal and immunologically disturbed pregnancies. ILC antigen presentation potential was characterized by flow cytometry and qPCR. We discovered that the distribution of ILC subsets changed during both human and murine pregnancy. Moreover, the pregnancy was accompanied by reduced MHCII expression in splenic ILCs during normal pregnancy (CBA/J × BALB/c; good outcome pregnant mice; GOPM) but increased in splenic and intestinal ILCs of CBA/J × DBA/2J mice. In vitro, splenic ILCs from pregnant mice increased MHCII expression after stimulation with IL-1β and IL-23. In contrast, uterine ILCs displayed lower MHCII expression, which remained unchanged after stimulation. Finally, pregnancy-related factors and hormones present in the uterine environment reduced antigen presentation potential of human ILCs in vitro. Together, these data indicate that, during pregnancy, peripheral and especially uterine ILCs adapt their antigen presenting potential to maintain a level of tolerance and support pregnancy.

Download Full-text

Cranial crassicaudiasis in two coastal dolphin species from South Africa is predominantly a disease of immature individuals

Diseases of Aquatic Organisms ◽

10.3354/dao03468 ◽

2020 ◽

Vol 139 ◽

pp. 93-102 ◽

Cited By ~ 3

Author(s):

MF Van Bressem ◽

P Duignan ◽

JA Raga ◽

K Van Waerebeek ◽

N Fraijia-Fernández ◽

...

Keyword(s):

South Africa ◽

Bone Development ◽

Bottlenose Dolphins ◽

Fatal Outcome ◽

Population Level ◽

Cape Coast ◽

Osteolytic Lesions ◽

Immune Mediated ◽

Significant Difference ◽

The Difference

Crassicauda spp. (Nematoda) infest the cranial sinuses of several odontocetes, causing diagnostic trabecular osteolytic lesions. We examined skulls of 77 Indian Ocean humpback dolphins Sousa plumbea and 69 Indo-Pacific bottlenose dolphins Tursiops aduncus, caught in bather-protecting nets off KwaZulu-Natal (KZN) from 1970-2017, and skulls of 6 S. plumbea stranded along the southern Cape coast in South Africa from 1963-2002. Prevalence of cranial crassicaudiasis was evaluated according to sex and cranial maturity. Overall, prevalence in S. plumbea and T. aduncus taken off KZN was 13 and 31.9%, respectively. Parasitosis variably affected 1 or more cranial bones (frontal, pterygoid, maxillary and sphenoid). No significant difference was found by gender for either species, allowing sexes to be pooled. However, there was a significant difference in lesion prevalence by age, with immature T. aduncus 4.6 times more likely affected than adults, while for S. plumbea, the difference was 6.5-fold. As severe osteolytic lesions are unlikely to heal without trace, we propose that infection is more likely to have a fatal outcome for immature dolphins, possibly because of incomplete bone development, lower immune competence in clearing parasites or an over-exuberant inflammatory response in concert with parasitic enzymatic erosion. Cranial osteolysis was not observed in mature males (18 S. plumbea, 21 T. aduncus), suggesting potential cohort-linked immune-mediated resistance to infestation. Crassicauda spp. may play a role in the natural mortality of S. plumbea and T. aduncus, but the pathogenesis and population level impact remain unknown.

Download Full-text