Cell- and nuclear-penetrating anti-dsDNA autoantibodies have multiple arginines in CDR3 of VH and increase cellular level of pERK and Bcl-2 in mesangial cells

Autoantibodies in systemic sclerosis: From disease bystanders to pathogenic players

Autoantibodies (Aab) are recognized as key indicators in the diagnosis, classification, and monitoring of systemic autoimmune diseases (AID). Recent studies have expanded knowledge through the discovery of new antigenic targets, advanced methods for measuring Aab levels, and understanding their possible pathogenic roles in AID. This narrative review uses systemic sclerosis (SSc) as an example to highlight the importance of Aab associated with HEp-2 immunofluorescence assay positivity (traditionally referred as antinuclear antibodies [ANA]), exploring recent developments in the field. Firstly, we outline the various types of ANA found in SSc and their links with specific disease features. Newly discovered antibodies shed light on SSc cases where Aab had previously gone unidentified. Secondly, we emphasize the necessity for novel quantitative techniques to track Aab levels over time by gathering data regarding the timing of Aab occurrence relative to SSc symptoms and the relationships between Aab concentrations and disease severity. Finally, we discuss the experimental findings suggesting a potential direct role of Aab in the development of SSc. The advancements surrounding Aab provide insights into new disease mechanisms and may lead to innovative diagnostic and treatment approaches.

Unravelling the TCRβ repertoire: a key to unlocking the immunopathogenesis and precision medicine in SLE

OBJECTIVES

SLE is a multifaceted autoimmune disorder with a complex pathogenesis involving genetic, environmental and hormonal factors, which converge on immune dysregulation. The T cell receptor (TCR) repertoire's role in SLE has garnered significant interest due to its potential in both diagnostics and therapeutics. Our study aimed to delineate the variances in the TCRβ repertoire between patients with SLE and healthy individuals, correlating these differences with the severity and subtypes of SLE.

METHODS

We conducted an analysis of blood samples from 50 treatment-naive patients with SLE and 50 healthy donors, employing RNA extraction, high-throughput sequencing and subsequent bioinformatics analysis.

RESULTS

Our findings revealed significant alterations in TRBV and TRBJ gene usage frequencies, indicative of a skewed TCR repertoire in patients with SLE. Notably, nine hub TRBV genes were identified as potential biomarkers for SLE with high diagnostic accuracy. Furthermore, we observed a reduction in TCR diversity, characterised by a lower diversity 50 value and increased clonal expansion, which correlated with disease severity.

CONCLUSIONS

The TCRβ repertoire is significantly altered in SLE, with potential implications for diagnostics and therapeutics. The identified hub genes may serve as novel biomarkers for SLE, and the findings contribute to the understanding of the immunopathogenesis of the disease.

An Emerging Role for Anti-DNA Antibodies in Systemic Lupus Erythematosus

Anti-DNA antibodies are hallmark autoantibodies produced in systemic lupus erythematosus (SLE), but their pathogenetic role is not fully understood. Accumulating evidence suggests that some anti-DNA antibodies enter different types of live cells and affect the pathophysiology of SLE by stimulating or impairing these cells. Circulating neutrophils in SLE are activated by a type I interferon or other stimuli and are primed to release neutrophil extracellular traps (NETs) on additional stimulation. Anti-DNA antibodies are also involved in this process and may induce NET release. Thereafter, they bind and protect extracellular DNA in the NETs from digestion by nucleases, resulting in increased NET immunogenicity. This review discusses the pathogenetic role of anti-DNA antibodies in SLE, mainly focusing on recent progress in the two research fields concerning antibody penetration into live cells and NETosis.

"Untargeting" autoantibodies using genome editing, a proof-of-concept study

Autoantibodies (AAbs) are useful biomarkers and many have direct pathogenic role. Current standard therapies for elimination of specific B/plasma-cell clones are not fully efficient. We apply CRISPR/Cas9 genome-editing to knockout V(D)J rearrangements that produce pathogenic AAbs in vitro. HEK293T cell-lines were established stably expressing a humanized anti-dsDNA Ab (clone 3H9) and a human-derived anti-nAChR-α1 Ab (clone B12L). For each clone, five CRISPR/Cas9 heavy-chain's CDR2/3-targeting guided-RNAs (T-gRNAs) were designed. Non-Target-gRNA (NT-gRNA) was control. After editing, levels of secreted Abs were evaluated, as well as 3H9 anti-dsDNA and B12L anti-AChR reactivities. T-gRNAs editing decreased expression of heavy-chain genes to ∼50-60%, compared to >90% in NT-gRNA, although secreted Abs levels and reactivity to their respective antigens in T-gRNAs decreased ∼90% and ∼ 95% compared with NT-gRNA for 3H9 and B12L, respectively. Sequencing indicated indels at Cas9 cut-site, which could lead to codon jam, and consequently, knockout. Additionally, remaining secreted 3H9-Abs presented variable dsDNA reactivity among the five T-gRNA, suggesting the exact Cas9 cut-site and indels further interfere with antibody-antigen interaction. CRISPR/Cas9 genome-editing was very effective to knockout the Heavy-Chain-IgG genes, considerably affecting AAbs secretion and binding capacity, fostering application of this concept to in vivo models as a potential novel therapeutic approach for AAb-mediated diseases.

Nanobodies as molecular imaging probes

Camelidae derived single-domain antibodies (sdAbs), commonly known as nanobodies (Nbs), are the smallest antibody fragments with full antigen-binding capacity. Owing to their desirable properties such as small size, high specificity, strong affinity, excellent stability, and modularity, nanobodies are on their way to overtake conventional antibodies in terms of popularity. To date, a broad range of nanobodies have been generated against different molecular targets with applications spanning basic research, diagnostics, and therapeutics. In the field of molecular imaging, nanobody-based probes have emerged as a powerful tool. Radioactive or fluorescently labeled nanobodies are now used to detect and track many targets in different biological systems using imaging techniques. In this review, we provide an overview of the use of nanobodies as molecular probes. Additionally, we discuss current techniques for the generation, conjugation, and intracellular delivery of nanobodies.

Autoantigen spermatid nuclear transition protein 1 enhances pro-inflammatory cytokine production stimulated by anti-DNA autoantibodies in macrophages

Introduction

Lupus nephritis (LN), a severe manifestation of systemic lupus erythematosus (SLE), is associated with high fatality rate in patients. The pathogenesis of lupus nephritis is complex and has not been fully elucidated. Kidney inflammation, renal cell damage, and accumulation of immune complexes in the glomerular basement membrane often occur in patients with lupus nephritis. Spermatid nuclear transition protein 1 (TNP1) might be a potentially interesting autoantigen in exploring the pathogenesis and therapy of lupus nephritis.

Objective

This study aimed to explore the effect of TNP1 and its complexes with anti-double-stranded DNA antibodies on the levels of interleukin-6 (IL-6) and interferon-α (IFN-α) in vitro.

Methods

We studied the effect of the synthetic peptide of the autoantigen on the pathogenic characteristics of the G2-6 and G5-8 antibodies in mouse macrophages, using enzyme-linked immunosorbent assay, quantitative RT-PCR, western blotting, and flow cytometry.

Results

The antibodies exhibited cross-reactivity to spermatid TNP1 in direct-binding and competitive enzyme-linked immunosorbent assay. Results of quantitative RT-PCR and western blotting revealed that the antibodies alone enhanced the levels of IL-6 and IFN-α transcripts and proteins, respectively. Flow cytometry revealed that treatment with the autoantigen enhanced the cell-penetrating activities of G2-6 and G5-8 and remarkably increased the cytokine levels.

Conclusion

TNP1 enhanced the cell-penetrating activities of anti-dsDNA auto-Abs, G2-6 and G5-8, and remarkably increased the levels of IL-6 and IFN-α in macrophages, suggesting that TNP1 and cell-penetrating pathogenic anti-dsDNA auto-Abs is potential targets for future therapeutic approaches to treat LN/SLE.

Antinuclear Autoantibodies in Health: Autoimmunity Is Not a Synonym of Autoimmune Disease

The incidence of autoimmune diseases is increasing. Antinuclear antibody (ANA) testing is a critical tool for their diagnosis. However, ANA prevalence in healthy persons has increased over the last decades, especially among young people. ANA in health occurs in low concentrations, with a prevalence up to 50% in some populations, which demands a cutoff revision. This review deals with the origin and probable physiological or compensatory function of ANA in health, according to the concept of immunological clearance, theory of autoimmune regulation of cell functions, and the concept of functional autoantibodies. Considering ANA titers ≤1:320 as a serological marker of autoimmune diseases seems inappropriate. The role of anti-DFS70/LEDGFp75 autoantibodies is highlighted as a possible anti-risk biomarker for autoimmune rheumatic disorders. ANA prevalence in health is different in various regions due to several underlying causes discussed in the review, all influencing additive combinations according to the concept of the mosaic of autoimmunity. Not only are titers, but also HEp-2 IFA) staining patterns, such as AC-2, important. Accepting autoantibodies as a kind of bioregulator, not only the upper, but also the lower borders of their normal range should be determined; not only their excess, but also a lack of them or "autoimmunodeficiency" could be the reason for disorders.

Harnessing SLE Autoantibodies for Intracellular Delivery of Biologic Therapeutics

Intracellular delivery of therapeutic antibodies is highly desirable but remains a challenge for biomedical research and the pharmaceutical industry. Approximately two-thirds of disease-associated targets are found inside the cell. Difficulty blocking these targets with available drugs creates a need for technology to deliver highly specific therapeutic antibodies intracellularly. Historically, antibodies have not been believed to traverse the cell membrane and neutralize intracellular targets. Emerging evidence has revealed that anti-DNA autoantibodies found in systemic lupus erythematosus (SLE) patients can penetrate inside the cell. Harnessing this technology has the potential to accelerate the development of drugs against intracellular targets. Here, we dissect the mechanisms of the intracellular localization of SLE antibodies and discuss how to apply these insights to engineer successful cell-penetrating antibody drugs.

Fibroblast growth factor inducible 14 signaling facilitates anti-dsDNA IgG penetration into mesangial cells

Anti-double-stranded DNA (dsDNA) antibodies induce renal damage in patients with systemic lupus erythematosus by triggering fibrotic processes in kidney cells. However, the precise mechanism underlying penetration of anti-dsDNA immunoglubolin G (IgG) into cells remains unclear. This study was designed to investigate the effect of tumor necrosis factor-like weak inducer of apoptosis (TWEAK)/fibroblast growth factor inducible 14 (Fn14) signaling on anti-dsDNA IgG penetration into cells. Mesangial cells were cultured in vitro, and stimulated with TWEAK and anti-dsDNA IgG. The results revealed that TWEAK dose-dependently enhanced cellular internalization of anti-dsDNA IgG and the expression of high-mobility group box 1 (HMGB1). In addition, TWEAK and anti-dsDNA IgG synthetically downregulate suppressor of cytokine signaling 1, and induce the expression of various fibrotic factors. Furthermore, inhibition of HMGB1 attenuates the enhancement effect of TWEAK on anti-dsDNA IgG internalization. The TWEAK upregulation of HMGB1 involves the nuclear factor-κB and phosphatidylinositide 3-kinase/protein kinase B pathways. Therefore, TWEAK/Fn14 signaling contributes to the penetration of anti-dsDNA IgG and relevant fibrotic processes in mesangial cells.

Clinical aspects and risk factors of lupus nephritis: a retrospective study of 156 adult patients

Objective

To analyze the clinical manifestations, laboratory indexes, disease activity, and pathological types of lupus nephritis (LN) in adult patients.

Methods

We retrospectively analyzed the clinical manifestations, laboratory indexes, and pathological classifications of 156 adult patients first diagnosed with LN between July 2013 and November 2017. Patients were categorized according to the following criteria: active or inactive LN, LN with or without renal damage, and mild or severe LN.

Results

Immunoglobulin G and A levels, 24-hour proteinuria, and anti-dsDNA, anti-Sm, and anti-ribosomal P protein antibody positivity rates were all significantly increased in patients with active LN compared with inactive LN. Anti-dsDNA antibody positivity and 24-hour proteinuria were significantly increased, whereas hemoglobin, serum albumin, and C3 and C4 levels were significantly decreased in patients with LN and renal damage compared with those without renal damage. Anti-dsDNA and anti-Sm antibody positivity rates and 24-hour proteinuria were significantly increased, while hemoglobin, serum albumin, C3 and C4 levels, and estimated glomerular filtration rate were significantly decreased in patients with severe LN compared with patients with mild LN.

Conclusions

LN can display various clinical manifestations, laboratory indexes, levels of disease activity, and pathological types in adult patients.

The Predictive Value of Autoantibody Spectrum on Organ Damage in Patients With Systemic Lupus Erythematosus

OBJECTIVES

This study aims to investigate the positive detection rate and predictive value of autoantibodies, including anti-double stranded deoxyribonucleic acid (anti-dsDNA) antibodies, anti-histone antibodies (AHAs), anti-ribosomal (anti-Rib) P antibodies, anti-Smith (anti-Sm) antibodies, anti-U1 ribonucleoprotein (anti-U1RNP) antibodies, anti-Sjögren's syndrome type A antibodies and anti-Sjögren's syndrome type B antibodies, on organ damage in patients with systemic lupus erythematous (SLE).

PATIENTS AND METHODS

A total of 225 patients with SLE (37 males, 188 females; mean age 37.4±15.9 years; range, 7 to 80 years) were evaluated retrospectively. Statistical analysis was performed to obtain the positive detection rate of autoantibodies and to investigate the predictive value.

RESULTS

There were statistically significant differences of positive anti-dsDNA antibodies in renal damage, photosensitization, hematological abnormalities and serositis (p<0.05) and a statistically significant difference of positive AHAs in photosensitization (p<0.05). There was statistically significant difference of positive anti-U1RNP antibodies in renal damage (p<0.05). There were also statistically significant differences of positive anti-Smith antibodies in renal damage, arthritis, photosensitization, oral ulcers, hematological abnormalities and serositis (p<0.05) and of positive anti-Rib antibodies in renal damage, arthritis, photosensitization, malar rash, hematological abnormalities and serositis (p<0.05). However, there were no statistically significant differences of positive anti-Sjögren's syndrome type B antibodies and anti-Sjögren's syndrome type A antibodies in renal damage, arthritis, malar rash, neuropsychiatric disorders, hematological abnormalities and serositis (p>0.05).

CONCLUSION

Autoantibody spectrum is an important serological basis for SLE diagnosis. There are differences in the autoantibodies distribution of SLE patients with different organ damage, suggesting a certain clinical value for prediction of organ damage in SLE.

Anti-double Stranded DNA Antibodies: Origin, Pathogenicity, and Targeted Therapies

Systemic lupus erythematosus (SLE) is characterized by high-titer serological autoantibodies, including antibodies that bind to double-stranded DNA (dsDNA). The origin, specificity, and pathogenicity of anti-dsDNA antibodies have been studied from a wider perspective. These autoantibodies have been suggested to contribute to multiple end-organ injuries, especially to lupus nephritis, in patients with SLE. Moreover, serum levels of anti-DNA antibodies fluctuate with disease activity in patients with SLE. By directly binding to self-antigens or indirectly forming immune complexes, anti-dsDNA antibodies can accumulate in the glomerular and tubular basement membrane. These autoantibodies can also trigger the complement cascade, penetrate into living cells, modulate gene expression, and even induce profibrotic phenotypes of renal cells. In addition, the expression of suppressor of cytokine signaling 1 is reduced by anti-DNA antibodies simultaneously with upregulation of profibrotic genes. Anti-dsDNA antibodies may even participate in the pathogenesis of SLE by catalyzing hydrolysis of certain DNA molecules or peptides in cells. Recently, anti-dsDNA antibodies have been explored in greater depth as a therapeutic target in the management of SLE. A substantial amount of data indicates that blockade of pathogenic anti-dsDNA antibodies can prevent or even reverse organ damage in murine models of SLE. This review focuses on the recent research advances regarding the origin, specificity, classification, and pathogenicity of anti-dsDNA antibodies and highlights the emerging therapies associated with them.

Immunoglobulin gene analysis as a tool for investigating human immune responses

The human immunoglobulin repertoire is a hugely diverse set of sequences that are formed by processes of gene rearrangement, heavy and light chain gene assortment, class switching and somatic hypermutation. Early B cell development produces diverse IgM and IgD B cell receptors on the B cell surface, resulting in a repertoire that can bind many foreign antigens but which has had self-reactive B cells removed. Later antigen-dependent development processes adjust the antigen affinity of the receptor by somatic hypermutation. The effector mechanism of the antibody is also adjusted, by switching the class of the antibody from IgM to one of seven other classes depending on the required function. There are many instances in human biology where positive and negative selection forces can act to shape the immunoglobulin repertoire and therefore repertoire analysis can provide useful information on infection control, vaccination efficacy, autoimmune diseases, and cancer. It can also be used to identify antigen-specific sequences that may be of use in therapeutics. The juxtaposition of lymphocyte development and numerical evaluation of immune repertoires has resulted in the growth of a new sub-speciality in immunology where immunologists and computer scientists/physicists collaborate to assess immune repertoires and develop models of immune action.

Peptide Sharing Between Viruses and DLX Proteins: A Potential Cross-Reactivity Pathway to Neuropsychiatric Disorders

The present study seeks to determine potential associations between viral infections and neuropsychiatric diseases. To address this issue, we investigated the peptide commonalities between viruses that have been related to psychiatric and neurological disorders—such as rubella, human immunodeficiency virus, and herpesviruses—and human distal-less homeobox (DLX) proteins expressed in developing brain—namely, DLX1, DLX2, DLX5, and DLX6. Peptide matching analyses revealed a high degree of pentapeptide sharing. From an immunological perspective, this overlap is relevant because pentapeptides are endowed with immunogenicity and antigenicity—that is, they are immune determinants. Moreover, infection-induced immune cross-reactions might have functional, spatial, and temporal implications related to the functions and expression patterns of DLX1 and DLX5 in the fetal and adult human brain. In sum, our data support the hypothesis that viral infections may be linked to neuropsychiatric diseases through autoimmune cross-reactions caused by molecular mimicry between viral proteins and brain-specific DLX self-antigens.

Affinity maturation shapes the function of agonistic antibodies to peptidylarginine deiminase type 4 in rheumatoid arthritis

OBJECTIVES

The citrullinating enzyme peptidylarginine deiminase type 4 (PAD4) is the target of a polyclonal group of autoantibodies in patients with rheumatoid arthritis (RA). A subgroup of such antibodies, initially identified by cross-reactivity with peptidylarginine deiminase type 3 (PAD3), is strongly associated with progression of radiographic joint damage and interstitial lung disease and has the unique ability to activate PAD4. The features of these antibodies in terms of their T cell-dependent origin, genetic characteristics and effect of individual antibody specificities on PAD4 function remain to be defined.

METHODS

We used PAD4 tagged with the monomeric fluorescent protein mWasabi to isolate PAD4-specific memory B cells from anti-PAD4 positive patients with RA and applied single cell cloning technologies to obtain monoclonal antibodies.

RESULTS

Among 44 single B cells, we cloned five antibodies with PAD4-activating properties. Sequence analysis, germline reversion experiments and antigen specificity assays suggested that autoantibodies to PAD4 are not polyreactive and arise from PAD4-reactive precursors. Somatic mutations increase the agonistic activity of these antibodies at low calcium concentrations by facilitating their interaction with structural epitopes that modulate calcium-binding site 5 in PAD4.

CONCLUSIONS

PAD4-activating antibodies directly amplify a key process in disease pathogenesis, making them unique among other autoantibodies in RA. Understanding the molecular basis for their functionality may inform the design of future PAD4 inhibitors.

The deposition of anti-DNA IgG contributes to the development of cutaneous lupus erythematosus

Anti-DNA IgG is a hallmark of systemic lupus erythematosus and induces internal injuries in patients. It is known that cutaneous lupus erythematosus (CLE) involves the deposition of autoantibodies in the dermoepidermal junction of the skin and that anti-DNA IgG binds specifically to keratinocytes. However, the definite role of anti-DNA IgG in CLE remains unclear. The purpose of this study was to elucidate the effect of anti-DNA IgG on keratinocytes in CLE. Skin tissues were collected from patients with CLE and healthy controls. Also, murine anti-DNA IgG was incubated with frozen sections of murine skin or PAM212 keratinocytes. The chemotaxis of J774.2 macrophages was evaluated in special chambers with keratinocytes under anti-DNA IgG stimulation. Enzyme-linked immunosorbent assay, flow cytometry, Western blot, and surface plasmon resonance were used to quantitate the interaction between anti-DNA IgG and keratinocyte-related self-antigens. The results showed that anti-DNA IgG could be eluted from the lesional tissues of CLE patients, depending on the serum positivity. Murine anti-DNA IgG bound preferably to the dermoepidermal zones of normal skin and specifically to collagen III and the suppressor of cytokine signalling 1 (SOCS1) but not to Ro52. Moreover, the chemotaxis of macrophages was promoted by the incubation of anti-DNA IgG with keratinocytes. Interestingly, anti-DNA IgG exaggerated both the expression and the activation of fibroblast growth factor inducible 14 (Fn14) in keratinocytes and regulated SOCS1 signals in a time-dependent manner. In conclusion, anti-DNA IgG may contribute to the development of CLE through binding to keratinocyte-related antigens, exacerbating inflammatory infiltration, and modulating Fn14 and SOCS1 pathways.

TRIM21 and the Function of Antibodies inside Cells

Therapeutic antibodies targeting disease-associated antigens are key tools in the treatment of cancer and autoimmunity. So far, therapeutic antibodies have targeted antigens that are, or are presumed to be, extracellular. A largely overlooked property of antibodies is their functional activity inside cells. The diverse literature dealing with intracellular antibodies emerged historically from studies of the properties of some autoantibodies. The identification of tripartite motif (TRIM) 21 as an intracellular Fc receptor linking cytosolic antibody recognition to the ubiquitin proteasome system brings this research into sharper focus. We review critically the research related to intracellular antibodies, link this to the TRIM21 effector mechanism, and highlight how this work is exposing the previously restricted intracellular space to the potential of therapeutic antibodies.

Recent advances in the understanding of renal inflammation and fibrosis in lupus nephritis

Lupus nephritis is a potentially reversible cause of severe acute kidney injury and is an important cause of end-stage renal failure in Asians and patients of African or Hispanic descent. It is characterized by aberrant exaggerated innate and adaptive immune responses, autoantibody production and their deposition in the kidney parenchyma, triggering complement activation, activation and proliferation of resident renal cells, and expression of pro-inflammatory and chemotactic molecules leading to the influx of inflammatory cells, all of which culminate in destruction of normal nephrons and their replacement by fibrous tissue. Anti-double-stranded DNA (anti-dsDNA) antibody level correlates with disease activity in most patients. There is evidence that apart from mediating pathogenic processes through the formation of immune complexes, pathogenic anti-dsDNA antibodies can bind to resident renal cells and induce downstream pro-apoptotic, pro-inflammatory, or pro-fibrotic processes or a combination of these. Recent data also highlight the critical role of macrophages in acute and chronic kidney injury. Though clinically effective, current treatments for lupus nephritis encompass non-specific immunosuppression and the anti-inflammatory action of high-dose corticosteroids. The clinical and histological impact of novel biologics targeting pro-inflammatory molecules remains to be investigated. Insight into the underlying mechanisms that induce inflammatory and fibrotic processes in the kidney of lupus nephritis could present opportunities for more specific novel treatment options to improve clinical outcomes while minimizing off-target untoward effects. This review discusses recent advances in the understanding of pathogenic mechanisms leading to inflammation and fibrosis of the kidney in lupus nephritis in the context of established standard-of-care and emerging therapies.

Anti-dsDNA antibodies and resident renal cells - Their putative roles in pathogenesis of renal lesions in lupus nephritis

Lupus nephritis affects up to 70% of patients with systemic lupus erythematosus and is an important treatable cause of kidney failure. Cardinal features of lupus nephritis include loss of self-tolerance, production of autoantibodies, immune complex deposition and immune-mediated injury to the kidney, resulting in increased cell proliferation, apoptosis, and induction of inflammatory and fibrotic processes that destroy normal nephrons. The production anti-dsDNA antibodies is a cardinal feature in lupus and their level correlates with disease activity. In addition to the formation of immune complexes thereby triggering complement activation, how anti-dsDNA antibodies home to the kidney and induce pathological processes in the renal parenchyma remain to be fully elucidated. Data from our laboratory and other investigators show that the properties of anti-dsDNA antibodies vary between patients and change over time, and that anti-dsDNA antibodies could bind directly to integral cell surface molecules such as annexin II or α-actinin, or indirectly through chromatin material deposited on the cell surface. The binding of anti-dsDNA antibodies to mesangial cells and proximal renal tubular epithelial cells triggers downstream inflammatory and fibrotic pathways, which include the activation of the PKC and MAPK signaling pathways, increased secretion of pro-inflammatory cytokines and matrix protein deposition that contribute to pathological processes in the renal parenchyma.