Free immunoglobulin light chains: A role in minimal change disease

The glomerular permeability factors in idiopathic nephrotic syndrome

It is currently postulated that steroid-sensitive idiopathic nephrotic syndrome (SSNS) and steroid-resistant idiopathic nephrotic syndrome (SRNS), which are not related to the mutation of a gene coding for podocyte structures or for glomerular basement membrane proteins, result from a circulating factor affecting podocyte shape and function. T lymphocytes have for a long time been suspected to be involved in the pathophysiology of these diseases. The successful treatment of steroid-dependant nephrotic syndrome with rituximab suggests a potential role for B lymphocytes. Clinical and experimental data indicate roles for cytokines IL-13, TNFα, circulating cardiotrophin-like cytokine factor 1 (member of the IL-6 family), circulating hemopexin, radical oxygen species, and the soluble urokinase-type plasminogen activator receptor (suPAR) in the development of nephrotic syndrome. Podocyte metabolism modifications-leading to the overexpression of the podocyte B7-1antigen (CD 80), hypoactivity of the podocyte enzyme sphingomyelin phosphodiesterase acid-like 3 b (SMPDL3b), and to the podocyte production of a hyposialylated form of the angiopoietin-like 4 (Angptl4)-are mechanisms possibly involved in the changes in the podocyte cytoskeleton leading to SSNS and or SRNS. Different multifactorial pathophysiological mechanisms can be advocated for SSNS and SRNS. The present paper reviews the experimental and clinical data upon which the different hypotheses are based and reports their possible clinical applications.

Toll-like receptor 3 expression and function in childhood idiopathic nephrotic syndrome

The efficacy of steroids and immunosuppressive treatments in idiopathic nephrotic syndrome (INS) hints at the implication of immune cells in the pathophysiology of the disease. Toll-like receptor (TLR) dysfunctions are involved in many kidney diseases of immune origin, but remain little described in INS. We investigated the expression and function of TLRs in peripheral blood mononuclear cells (PBMC) of INS children, including 28 in relapse, 23 in remission and 40 controls. No child had any sign of infection, but a higher Epstein-Barr virus viral load was measured in the PBMC of relapsing patients. TLR-3 expression was increased in B cells only during INS remission. There was a negative correlation between proteinuria and TLR-3 expression in total and the main subsets of PBMC from INS patients. The expression of TLR-8 was also increased in both CD4(+) T cells and B cells in INS remission. There was a negative correlation between proteinuria and TLR-8 expression in total PBMC, CD4(+) T cells and B cells of INS patients. Nevertheless, TLR-3 and TLR-8 expression was normalized in all PBMC subsets in an additional group of 15 INS patients in remission with B cell repletion after rituximab therapy. Paradoxically, interferon (IFN) regulatory factor 3 transactivation was increased in PBMC of all INS patients. In-vitro secretion of IFN-α and interleukin 6 were increased spontaneously in PBMC of INS remission patients, whereas PBMC from all INS patients displayed an impaired IFN-α secretion after TLR-3 stimulation. Thus, TLR-3 pathway dysfunctions may be closely involved in INS pathogenesis.

Physiopathology of idiopathic nephrotic syndrome: lessons from glucocorticoids and epigenetic perspectives

Idiopathic nephrotic syndrome (INS) has been studied for decades in attempt to understand the physiopathological mechanisms explaining the disease. It is recognized as a multifactorial disease, with immunological components targeting kidney functions. Many hypotheses have been discussed or tested, including the role of a circulating factor, polymorphisms of genes implicated in lymphocyte maturation and differentiation, and DNA epigenetic modifications. In the present review, the data supporting these different (and probably combinatorial) hypotheses have been reviewed in order to identify and discuss the possible pathways implicated in the physiopathology of INS.

Minimal change disease associated with MALT lymphoma

Low-grade Extranodal Marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue, a subtype of non-Hodgkin's Lymphoma, involving the kidney is a rare clinical entity. Association of Minimal change disease nephrotic range proteinuria with Hodgkin's lymphoma is well described, however is extremely uncommon with non-Hodgkin's lymphoma. We describe a patient who presented with nephrotic syndrome and a kidney biopsy revealed marginal zone lymphoma and diffuse epithelial foot process effacement. He showed dramatic response to a combination therapy with cyclophosphamide, corticosteroids, and Rituximab.

Rituximab efficiency in children with steroid-dependent nephrotic syndrome

Although most patients with idiopathic nephrotic syndrome (NS) respond to steroid treatment, development of steroid dependency may require a long-term multidrug therapy including steroid and calcineurin inhibitor. Rituximab was shown to allow a reduction of the doses of steroid and immunosuppressive drugs in those patients. In the present series, 22 patients with steroid-sensitive, but steroid-dependent nephrotic syndrome were treated with rituximab. Rituximab reduced B cell count down to an undetectable level in all patients. A second treatment was necessary in 18 patients in order to maintain B cell depletion for up to 18 months. B cell depletion lasted 4.9 to 26 months (mean 17.2 months). At last follow-up, 9 patients were in remission without oral steroid or calcineurin inhibitor, although B cell count had recovered for 2.9 to 17 months (mean 9.5 months). A remission under ongoing B cell depletion was observed in 10 other patients in the absence of oral steroid or calcineurin inhibitor. Rituximab failed in 2 patients and 1 refused any additional treatment, despite B cell recovery and relapse. Toxicity of rituximab was limited to reversible cytokine shock in 2 patients and reversible neutropenia in 1 patient. No severe infection was observed.