The immunogenetic mechanism of renal injury

George P Lai

Basic component of renal immune response

• Humoral response– Anti-GBM disease– Immune complex disease

• The cellular response– T cells and macrophages– Particularly in crescent formation and

tubulointerstitial disease

Adaptive immunity

To Establish Relationship

• A present when B occur (TNF elevated when GN occur)

• B improved when A removed (TNF knock out model)

• A transfer will make B occur (Transfer model, transgenic model)

Animal Models

• NTN model (Nephrotoxic nephritis)-Crescentic GN– Rat: WKY (macrophage dependent)– Mouse: C57BL/6 (T cell/Th1 dependent)– Rabbit

• EAG model (Experimental autoimmune glomerulonephritis)

• Thy 1.1 model (mesangial proliferative GN)• Heymann’s nephritis—MGN• Puromycin induced nephrosis--MCD

Main players in GN

• Macrophage

• T cells

• B cells

• Neutrophil

• Endothelial cells

• Mesangial cells

The results come from

• The initiating events

• The genetic background

• The immune responses (mechanisms)– Humoral immunity– Cellular immunity

• The glomerular responses

Initiating Events

• Infectious antigen: streptococcus, virus (HBV, HCV, HIV)– Circulating immune complex – Autoimmune response

• Non-infectious antigen– Drug, toxin

• Modified by genetic background– Suspectibility (DRB1 in goodpasture’s disease; DR3 in MGN; 1-

antitrypsin deficiency in Wegener’s granulomatosis)– Severity– Response to therapy– Outcome

Humoral mechanisms of renal injury

• Predominantly IgG (Except in IgA nephropathy)– Trapping of circulating immune complex

• Subendothelial, mesangial areas

– In situ formation of immune complex• Fixed glomerular antigen(anti-basement membrane

antibody)

• Planted antigen (PSGN, Lupus, Goodpasture, MGN)

Immunoglobulin

Immunoglobulin classes

Injury induced by antibody alone

• Complement independent• Anti-nephrin antibody

– A slip-pore diaphragm antigen

– Offering insight into glomerular permeability barrier

• Nephrotoxic nephritis– Cathepsins B and Cathepsins L

– Cysteine proteinases inhibitor such as E-64, Ep 475 reduced proteinuria

Goodpasture’s syndrome

Injury mediated by C5b-9

• C5b-9 deposition in – subepithelial area induce proteinuria

• Activate epithelial cell---overproduction of oxidant, proteases, growth factors such as PDGF

– Subendothelial and mesangial area• Adhesion molecule• Proinflammatory cytokines such as IL-1• Growth factors (TGF-1)

• C3 NeF-autoantibody nephritic factor 3– Autoantibody that stabilize the alternative pathway C3

convertases---membranoproliferative GN type II

C5a

• C5a a chemotaxic factor for neutrophil• Adhesion molecule upregulated in endothelial cell

and neutrophil Selectin, ICAM-1, VCAM-1• Evidences of neutrophil in glomerular disease

– PMN can injure glomeruli and degrade GBM in vitro– PMN are present in glomerular disease– PMN depletion reduces glomerular injury in

experimental models such as nephrotoxic nephritis– PMN repletion reconstitutes injury in PMN-depleted

rats with nephritis

Neutrophil

• Evidences of neutrophil in glomerular disease– PMN can injure glomeruli and degrade GBM in vitro

– PMN are present in glomerular disease

– PMN depletion reduces glomerular injury in experimental models such as nephrotoxic nephritis

– PMN repletion reconstitutes injury in PMN-depleted rats with nephritis

Neutrophil induced glomerular injury

• Neutrophil induced disease by– Release Oxidants: OH, O2

-, H2O2

– Proteases: lysozyme, defensins – Lipid mediators: thromboxane A2, Leukotriene

B4, – Cytokines: IL-1 TNF, IL-6– Reactive nitrogen species: NO, peroxynitrite

Platelets

• Evidences of platelet involvement– Platelet activation in MGN, Lupus, MPGN,

FSGN, DM nephropathy– Elevated platelet secretory products: -

thromboglobulin, PF4– Renal localization of platelets:

mesangiocapillary glomerulonephritis, FSGN, Lupus nephritis

Platelets induced renal injury

-granule : PDGF, TGF-, HGF, EGF

• Lysosomal enzymes– Proeinases: cathepsin, collagenase, neutral protease, acid

hydrolases

• Lipid and eicosanoids– Phospholipase A2– Prostaglandin E2– Thromboxane A2– Leukotrienes

Cellular immunity

• T cell and macrophages• T cell activation and antigen presentation

– Antigen presenting cells: dendritic cells, B cells and macrophage

– MHC class I—CD8; MHC class II—CD 4– Costimulatory signals (Signal II)

• B7.1, B7.2—CD28; LFA-1---ICAM family; CD40—CD40L

– Immunological synapse

Macrophage and T cell

T cell Macrophage

T cell receptors

Immunologic synapse

Affinity constants and Roles of Co-receptors in TCR binding.

T helper and cytotoxic cells

Cellular immunity

• T cells are important in transplantation biology and crescentic glomerulonephritis

• T cell effector functions– Cytotoxic T cell: perforin, FasL– Naïve T cell---Activated Th0 cell

• (IL12) Activated Th1 cells: IL-2, IFN- TNF-• (IL-4) Activated Th2 cells: IL-4 IL-5, IL-10, IL-11,

humoral immunity

Macrophage

Cellular immunity

• Macrophages– Multiple roles in glomerulonephritis

• Antigen presenting cells

• Effector cells (activation and proliferation in glomeruli)

• Profibrotic activity: Tissue factor, procoagulant factors(fibrin)

• Tissue repairing:phagocytosis, removing apoptotic cells, secreting HGF, VEGF

Mediators macrophages secrete

• Reactive oxygen species• Nitric oxide• Metaloproteinases• Complements• Procoagulant activity• Thromboxane/eicosanoids• IL-1, IL-4, IL-10, IL-12• TNF-• MIF• PDGF, TGF-, Fibronectin, FGF-2• PAF

Glomerular response to immune injury

• Four factors are important– Site of immune event happen

• Subendothelium—attract severe inflammation and decrease GFR such as PSGN and Type IV lupus nephritis

• Mesangium– mesangial proliferation and matrix deposition such as IgA nephropathy

• Subepithelium—few systemic reactions; injury occurred through C5-9 deposition and local release of mediators

Glomerular response to immune injury

• The mechanism of deposition– In situ immune complex formation is more damaging

than pass trapping circulating immune complex

• The property of deposited antibody– IgG>IgA>IgM

• The quantity of IgG deposition beyond mesangium> within mesangium

Glomerular intrinsic cells

• Mesangial cells, Endothelial cells, epithelial cells• Mesangial cells:

– Best studied among the three

– Proliferate in response to injury such as IgA nephropathy, Lupus nephritis

– Release proinflammatory mediator• Oxidants and proteases

• Cytokines: MCP-1, growth factor(PDGF), prostaglandins, leukotrienes, endothelin, nitric oxide

Glomerular intrinsic cells

• Glomerular epithelial cells– Important in pathogenesis of minimal change

disease, focal sclerosing GN, MGN, HIV related GN

– Release mediators such as hydrogen peroxide and matrix components

– Don’t proliferate in response to mitogen

Glomerular intrinsic cells

• Endothelial cells– Lease studied– Important in Hemolytic uremic syndrome,

Thrombotic thrombocytopenic purpura, HCV related renal disease, cryoglobulinemia, lupus nephritis

– Adhesion molecule, angiogenesis, production of pro & anti-coagulant molecules

Cellular mediator of interstitial disease

• Tubularinterstitial injury is the common pathway to end stage renal disease

• Involved T cell, dendritic cell and macrophage, fibroblast• Tubular interstitial nephritis without glomerulonephritis

may due to – expression of latent protein from virus-herpex or lentivirus– Lose immune tolerance– Tubular reclamation– Secretion of chemokine and cytokine

• Tubulointerstitial nephritis after glomerulonephritis– Heavy proteinuria, activate complement, chemokine, cytokine

during tubular reclamation

Humoral mediator of interstitial nephritis

• Source: adjacent somatic cell(epithelial cell, dendritic cell)

• Mediators: prostaglandin, leukotriene nitric oxide endothelin, complement, protease, oxidants

• Persistence is important (1-2 weeks)• Fibrogenesis—TGF-, angiotensinII, PDGF,

plasminogen activator inhibitor 1, fibroblast specific protein 1.