Lupus Nephritis Flashcards
Lupus Nephritis
Epidemiology
Epidemiology
It is estimated that 60% of patients with SLE will develop clinically significant LN in the course of the disease.
Lupus Nephritis
Epidemiology
Age:
The majority of patients who develop LN are younger than 55 years old.
Severe nephritis is more common in children than elderly patients.
Lupus Nephritis
Epidemiology
Gender difference (female-to-male ratio) is noted for female predominance and varies with age:
2: 1 in prepubertal children
4: 1 in adolescents
8 to 12:1 in adults
2:1 in adults age greater than 60
Lupus Nephritis
Epidemiology
Renal outcome portends worse prognosis in males than females.
Lupus Nephritis
Epidemiology
Race-related demographics:
SLE is more common in African Americans and Hispanics than whites.
Severe LN is more common in African Americans and Asians than in other ethnic groups.
Lupus Nephritis
Pathogenesis
Production of autoantibodies by mature B cells (plasma cells) against nuclear antigens (e.g., double stranded DNA (dsDNA), ribonucleoproteins, complement factors (e.g., C1q). This process may be driven by:
Antigenic mimicry: antibodies against bacterial or viral peptides cross-react to self-antigens.
Impaired clearance of apoptotic bodies
Lupus Nephritis
Pathogenesis
Production of autoantibodies by mature B cells (plasma cells) against nuclear antigens (e.g., double stranded DNA (dsDNA), ribonucleoproteins, complement factors (e.g., C1q). This process may be driven by:
Polyclonal hyperactivity of the B-cell system or defects of T-cell autoregulation leading to high antibody production
Anti-double stranded DNA (anti-dsDNA) antibody response driven by histone-specific T-helper cells
Lupus Nephritis
Pathogenesis:
IC deposition: deposition of circulating IC in GBM or direct binding of nucleosomal antigens to GBM followed by in situ autoantibody-binding activates both complement-dependent and independent inflammatory cascades.
Lupus Nephritis
IC clearance:
ICs are normally cleared by the C1 complement complex. Binding of C1 complex to IC leads to downstream complement activation and opsonization of the IC for phagocytosis.
Lupus Nephritis
IC clearance:
C1q is a component of the C1 complex. Upon binding of C1 complex to IC, C1 complex undergoes conformational change, exposing antigenic sites of C1q, which then leads to autoantibody formation against C1q. High autoantibody titers against C1q have been suggested to correlate with active lupus.
Lupus Nephritis
Inflammatory effects following impaired apoptotic bodies clearance and/or IC formations and roles of other inflammatory cells:
Neutrophils:
Neutrophils:
NETosis: a process whereby upon exposure to microorganisms, neutrophils release nuclear components, granule proteins, and chromatin to form an extracellular matrix (ECM), referred to as “neutrophil extracellular traps” (NETs) to “trap,” destroy, and clear the invading microorganisms.
Lupus Nephritis
Inflammatory effects following impaired apoptotic bodies clearance and/or IC formations and roles of other inflammatory cells:
Neutrophils:
Neutrophils:
NETs comprise of DNA and histones along with various peptides and proteinases such as high-mobility group protein box-1, cathelicidin, myeloperoxidase, neutrophil elastase, matrix metalloproteinase 9, and proteoglycan recognition protein short.
Lupus Nephritis
Inflammatory effects following impaired apoptotic bodies clearance and/or IC formations and roles of other inflammatory cells:
Neutrophils:
Neutrophils:
NETs may serve as a source of autoantigens in SLE. There are data to suggest that NETs are complement activators and can play a role in increasing C1q deposition.
Lupus Nephritis
Inflammatory effects following impaired apoptotic bodies clearance and/or IC formations and roles of other inflammatory cells:
Basophils:
Basophils:
Cross-linking of IgE to its receptors (FcκRI) on basophil surface leads to the secretion of histamine and proinflammatory cytokines by basophils.
Lupus Nephritis
Inflammatory effects following impaired apoptotic bodies clearance and/or IC formations and roles of other inflammatory cells:
Basophils:
There are data to suggest that increased titers of both dsDNA-IgE and dsDNA-IgG predict SLE disease activity better than dsDNA-IgG titers alone.
Lupus Nephritis
Inflammatory effects following impaired apoptotic bodies clearance and/or IC formations and roles of other inflammatory cells:
Basophils:
Activated basophils secrete cytokines (IL-4 and IL-6) and express the MHC-II and B cell-activating factor BAFF (also known as B-Lys), which can enhance plasma cell survival and autoantibody production amplification loop.
Lupus Nephritis
Inflammatory effects following impaired apoptotic bodies clearance and/or IC formations and roles of other inflammatory cells:
Basophils:
Other functions of activated basophils: promotion and regulation of TH2 adaptive immune responses, antigen presentation to T cells, plasma cell differentiation and support, monocyte polarization and recruitment, and inflammatory site organization.
Lupus Nephritis
Inflammatory effects following impaired apoptotic bodies clearance and/or IC formations and roles of other inflammatory cells:
Macrophages/monocytes:
Macrophages/monocytes:
NETs containing LL37 stimulate NLRP3 inflammasome in monocytes and result in IL-1β and IL-18 release, NETosis, and amplification of the proinflammatory state.
Lupus Nephritis
Inflammatory effects following impaired apoptotic bodies clearance and/or IC formations and roles of other inflammatory cells:
Macrophages/monocytes:
Macrophages/monocytes:
Polymorphism in the IL-18 gene promoter with associated increased IL-18 production may promote SLE susceptibility.
Lupus Nephritis
Inflammatory effects following impaired apoptotic bodies clearance and/or IC formations and roles of other inflammatory cells:
Autoreactive B-cells and T-cells due to defective regulatory mechanisms.
Lupus Nephritis:
Advances in SLE targeted therapy:
Advances in SLE targeted therapy:
Belimumab: human monoclonal antibody that selectively neutralizes B-cell activating factor (BAFF)
Lupus Nephritis:
Advances in SLE targeted therapy:
FDA approved for treatment of ANA/anti-dsDNA positive adults with high disease activity despite standard therapy
Lupus Nephritis:
Advances in SLE targeted therapy:
Short-term clinical trials suggest reduced SLE activity, flare rates, and corticosteroid need
Lupus Nephritis:
Advances in SLE targeted therapy:
Sifalimumab: human monoclonal antibody that inhibits several IFN-α subtypes1
Lupus Nephritis:
Advances in SLE targeted therapy:
Rontalizumab: humanized mouse monoclonal anti-IFN-α-antibody.
Lupus Nephritis:
Advances in SLE targeted therapy:
Omalizumab: recombinant humanized monoclonal antibody that blocks the binding of IgE to the FcεRI receptor.
Lupus Nephritis:
Diagnosis:
Routine laboratory findings:
Microscopic hematuria ± red blood cell casts, proteinuria ± nephrotic syndrome
Lupus Nephritis:
Diagnosis:
Routine laboratory findings cont’d:
Serologies: positive antinuclear antibody (sensitive, not specific), anti-Smith (specific), anti-dsDNA, hypocomplementemia (particularly low C3). Anti-Smith is specific for the diagnosis of SLE. Anti-dsDNA and hypocomplementemia correlate with kidney disease activity.
Lupus Nephritis:
Histopathology: International Society of Nephrology/Renal Pathology Society classification of LN:
Class I:
Minimal mesangial LN: normal glomeruli by LM; mesangial immune deposits by IF alone or by both IF and EM.
Lupus Nephritis:
Histopathology: International Society of Nephrology/Renal Pathology Society classification of LN:
Class II:
Mesangial proliferative LN: mesangial hypercellularity and matrix expansion on LM; mesangial immune deposits by both IF and EM.