Immunological abnormalities in patient with IgA nephropathy

T cell immunity and phagocytic activity were studied in the blood of patients with IgA nephropathy in order to clarify their roles in the pathogenesis of IgA nephropathy. The percentages of total T lymphocytes, helper T cell and suppressor T cells were significantly reduced in patients. A significantly elevated helper T cell/suppressor T cell ratio in patients showed a predominant reduction in suppressor T cells. There was a significant relationship between histologic findings and helper T cell/suppressor T cell ratio in patients. Natural Killer (NK) cell activity was significantly reduced but the lymphocyte response after phytohemagglutinin (PHA) stimulation was not in patients. ConA-induced suppressor cell activity was not depressed despite of a decrease in suppressor T cells in patients. Phagocytic activity of polymorphonuclear leucocytes (PMNs) ingesting yeasts was significantly reduced in patients. Also an inverse correlation was found between serum IgA levels and phagocytic activity of PMN. It is concluded that suppressor T cell defects, depressed phagocytic activity and impaired NK cell activity may play a role in the pathogenesis of IgA nephropathy.     

T-cell dysfunctions in IgA nephropathy: specific abnormalities in the regulation of IgA synthesis

This work was undertaken to determine the cellular abnormalities that could explain the high levels of serum IgA frequently found in patients with IgA nephropathy. Seventeen control subjects and twenty-seven patients who had received no therapy were studied. After in vitro pokeweed mitogen (PWM) stimulation, significantly higher amounts of IgA were produced by peripheral blood mononuclear cells (PBM) of patients when compared with those of the control group (560 +/- 97 vs 231 +/- 57 ng/ml, P less than 0.0025). No differences were observed in the synthesis of IgG and IgM. Twenty out of twenty-seven patients presented an increase in the percentages of OKT4+ cells (mean + 2 SD), in relation to the control group, with normal or elevated percentages of OKT8+ cells. The OKT4+/OKT8+ cell ratio was elevated in 12 out of 27 patients. All patients presented some abnormality in the generation of IgA-specific suppressor cells at variable doses of concanavalin A (Con A) on in vitro PWM-stimulated culture of PBM. In both assays low doses of Con A (2.5 micrograms/ml) induced a certain suppression of IgA synthesis in patients that was not observed in the majority of the control group. At these doses some patients also showed an enhancement in the synthesis of IgG and IgM. On the contrary, higher doses of Con A (50 micrograms/ml) produced significantly less IgA suppression than the controls. Normal IgA-suppression values were found at 10 micrograms/ml of Con A. T cells obtained from patients were significantly more efficient than T cells from controls in providing IgA-helper activity for normal allogeneic enriched B cells (P less than 0.025) in PWM-stimulated cocultures. These results show that patients with IgA nephropathy present, after mitogen stimulation in vitro, a specifically increased production of IgA as well as an augmentation in the activity of IgA-helper T cell and a deregulation on IgA-suppressor T-cell function. According to these data, it is suggested that the alteration observed in helper T cells might precede that of suppressor T cells. These immunoregulatory abnormalities might contribute to the pathogenesis of the disease.     

Increase of IgA specific helper T alpha cells in patients with IgA nephropathy.

Patients with IgA nephropathy show an emergence of IgA dominant circulating immune complexes (CIC) as well as increased levels of serum IgA and/or IgA bearing peripheral blood lymphocytes. In order to elucidate immunological aberrations responsible for the increased IgA synthesis in such patients, quantitative and qualitative analysis was performed on T alpha cells which have been recently identified as possessing IgA specific helper activity on human B cells. Three different methods were employed to quantitate T alpha cells. These methods included a rosette formation of T cells with either bovine red cells coated with the IgA fraction of anti-bovine red cell antiserum or those coated with TNP and anti-TNP IgA antibody, and an analysis of T cells combined with fluorescein conjugated human IgA myeloma protein. T alpha cells were sorted by a fluorescence activated cell sorter and co-cultured with a B cell rich fraction to evaluate whether there is a qualitative difference in IgA specific helper activity between patients and healthy adults. T alpha cells were significantly increased in patients with IgA nephropathy while there were no significant changes in patients with chronic proliferative glomerulonephritis without mesangial deposition of IgA. There was no qualitative difference in IgA specific helper activity of T alpha cells between patients and healthy adults. It is suggested that increased levels of T alpha cells in patients with IgA nephropathy may be responsible for increased synthesis of IgA in such patients.     

Immunoregulation in glomerulonephritis, Henoch--Schonlein purpura and lupus nephritis.

Immunoregulation was examined in normal controls and in patients with immune complex glomerulonephritis and lupus nephritis (SLE) using OKT monoclonal anti-bodies against helper (OKT4) and suppressor (OKT8) T cell subsets. Functional studies assessed T cell control of in vitro immunoglobulin synthesis by cultured peripheral blood mononuclear cells (PBMC). IgG and IgA synthesis was measured in unstimulated, pokeweed mitogen (PWM) stimulated and PWM + concanavalin A (Con A) stimulated cultures. Patients with primary membranous nephropathy (MN) and mesangial IgA nephropathy (IgA GN) were found to have elevated T4/T8 ratios secondary to a deficiency of the T8+ subset. Patients with SLE had low T4/T8 ratios. B cell activation with high spontaneous immunoglobulin synthesis was present in cell cultures from patients with SLE, IgA GN and Henoch-Schonlein purpura (HSP). Defective Con A inducible suppression of in vitro immunoglobulin synthesis was found in SLE, HSP and to a lesser extent, primary MN. Functional Con A inducible suppressor defects correlated with elevated T4/T8 ratios only in patients with MN. All four disorders appear to share disturbances of cellular immune response with various degrees of defective immune suppression; however, it is not clear from these studies whether the defects are primary or secondary phenomena.     

T cell subset alterations in idiopathic glomerulonephritis

Peripheral blood lymphocytes from 15 healthy controls and 59 patients with idiopathic glomerulonephritis were studied to determine whether an imbalance exists among human T cell subsets in these diseases. Twenty of the patients studied had a minimal change nephropathy (10 with nephrotic syndrome and 10 in sustained remission); 27 had a membranous glomerulonephritis (12 with nephrotic syndrome, six with isolated proteinuria and nine in complete remission); 12 patients had an IgA glomerulonephritis with heamaturia and mild proteinuria. Monoclonal antibodies directed at human T lymphocyte subsets termed OKT3, OKT4 and OKT8 were used in an indirect immunofluorescence assay in all cases. Patients with minimal change nephropathy, with or without nephrotic syndrome and patients with IgA glomerulonephritis showed mean values of OKT3⁺ cells (total peripheral T cells), helper OKT4⁺ cells, suppressor OKT8⁺ cells and OKT4⁺/OKT8⁺ cell ratio, in the normal range. Only the group of patients with membranous glomerulonephritis and nephrotic syndrome presented a mean OKT4⁺/OKT8⁺ ratio greater than the normal group (percentages: 2·43±0·3 vs 1·6±0·1 s.e.m.; P<0·02). This increased ratio was due to a reduction in the OKT8⁺ cell subset compared to the healthy subjects (percentages: 27·6±2·9 vs 36·8±1·4 s.e.m.; P<0·01). Our data shows that the functional lymphocyte disorders previously described in minimal change nephropathy and IgA glomerulonephritis are not due to a numerical imbalance of lymphocyte subsets. Such an imbalance of lymphocyte subsets was specifically observed in membranous glomerulonephritis with nephrotic syndrome. The true significance of this finding has to be clarified by longitudinal studies and functional tests.     

Lactate dehydrogenase (LDH) isoenzymes and proliferative activity of lymphoid cells--an immunocytochemical study.

The regulation of cytokine production and T cell proliferation by other cytokines is mandatory in mediating inflammatory responses but the full understanding is far from complete. We have previously reported increased production of IL-2 and IL-2 receptors (IL-2R) in IgA nephropathy. The present study was undertaken to examine other cytokine production during T cell activation in IgA nephropathy. Peripheral blood mononuclear cells (PBMC) from 17 IgA nephritic patients and 14 controls were cultured with phytohaemagglutinin and phorbol myristate acetate for 48 h for maximal cytokine production. IL-2Rs and IL-4 receptors (IL-4Rs) expressed on cultured PBMC were studied by a radioimmunoassay using monoclonal antibodies against these receptors. Although the total cellular IL-2R expression and percentages of T helper and T suppressor cells did not differ between the patients and controls, there was a significant increase in activated T helper cells expressing IL-2R in patients with IgA nephropathy. The total cellular IL-4R expression was elevated in IgA nephritic patients (P less than 0.005). IL-2 production by PBMC was raised in IgA nephritic patients compared with controls (P less than 0.05) but no difference in IL-4 or IL-6 production was observed. The interferon-gamma production by PBMC was significantly increased in patients with IgA nephropathy (P less than 0.025). No correlation was observed between individual cytokine levels. Our data suggest there are selective increases in cytokine production in IgA nephropathy.     

Increase of IgA-bearing lymphocytes in peripheral blood from patients with IgA nephropathy.

Aberration of IgA-bearing B lymphocytes in patients with IgA nephropathy has been investigated. Twelve patients with IgA nephropathy demonstrated a marked increase of IgA-bearing lymphocytes in peripheral blood, while ten patients with chronic proliferative glomerulonephritis without mesangial deposition of IgA showed normal amounts of IgA-bearing lymphocytes. The increase of IgA-bearing lymphocytes reflected that of IgA-producing lymphocytes, since lymphocytes obtained from patients with IgA nephropathy restored a high percentage of IgA-bearing cells in vitro after treatment with trypsin. Quantitation of IgA-bearing lymphocytes in peripheral blood is a useful method for screening of patients with IgA nephropathy.     

T-lymphocyte activation in IgA nephropathy: Serum-soluble interleukin 2 receptor level,interleukin 2 production,and interleukin 2 receptor expression by cultured lymphocytes

The present study was undertaken to examine the T-lymphocyte activation in IgA nephropathy. Serum-soluble interleukin 2 receptor (sIL2R) levels were studied in 29 IgA nephritic patients, 17 patients with chronic glomerulonephritis (non-IgA nephropathy), and 30 healthy controls during an infection-free period. No difference in serum sIL2R level was demonstrated among these three groups of subjects. However, the serum sIL2R levels of IgA nephritic patient rose significantly during clinical exacerbation with synpharyngitic macroscopic hematuria and the serum sIL2R levels fell when hematuria subsided. Mitogen-stimulated cellular interleukin 2 receptor (IL2R) expression, sIL2R release, and interleukin 2 (IL2) production were also examined in peripheral blood mononuclear cells (PBMC) cultured for 24–48 hr in 21 patients with IgA nephropathy, 17 patients with chronic glomerulonephritides, and 17 healthy controls. The total cellular IL2R expression and sIL2R release did not differ among these three groups of subjects. However, the individual T-cell subsets bearing IL2R were distinctly different between IgA nephritic patients and the other two groups of controls. IgA nephritic patients had increased activated CD4+ lymphocytes and reduced activated CD8+ lymphocytes. Furthermore, IL2 production in response to phytohemagglutinin and pokeweed mitogen stimulation was increased in lymphocytes from patients with IgA nephropathy. The IL2 production did not correlate with the quantities of cellular and sIL2R yet the cellular IL2R expression paralleled the sIL2R released by cultured lymphocytes. Our present study suggests that the T lymphocytes from patients with IgA nephropathy have a defect in overproduction of IL2 and increased activated T helper-cell subset upon mitogenic stimulation. Serum measurement of sIL2R could potentially be useful in monitoring the disease activity.     

Familial IgA nephropathy. Evidence of an inherited mechanism of disease

The evaluation of familial glomerulonephritis in patients with IgA nephropathy who were from central and eastern Kentucky resulted in the discovery of potentially related pedigrees containing 14 patients. An additional 17 members of the pedigrees had clinical glomerulonephritis, and 6 had "chronic nephritis" noted on their death certificates. Six patients with IgA nephropathy had a common ancestor. In addition, both parents of six patients with the disease came from families with other cases of IgA nephropathy. No single HLA haplotype or antigen was found in all the patients with IgA nephropathy. Our data on these pedigrees strongly support an inherited mechanism in the pathogenesis of IgA nephropathy in some patients.     

Increase of Peripheral Blood B Cells with Fc Receptor for IgA in Patients with IgA Nephropathy

A B-cell subset with Fc receptors for IgA (B alpha cells) has been observed in human peripheral blood. To investigate aberrations of B cells in a diseased state, the percentages of B alpha cells were enumerated in peripheral blood from patients with IgA nephropathy, which is characterized by preponderant deposition of IgA-dominant immune complexes in the glomerular mesangial area. The present study showed a significant increase in B alpha cells in peripheral blood from patients with IgA nephropathy but not in those with chronic proliferative glomerulonephritis without mesangial IgA deposition. Most Fc alpha R-bearing cells were observed in surface IgA bearing lymphocytes. No linear correlation was observed between the levels of serum IgA and the percentages of B alpha cells. The addition of aggregated IgA to cultures did not induce Fc alpha R-bearing B cells in vitro. It is postulated that B alpha cells might have some pathogenetic role in the development of IgA nephropathy and that some antigenic stimuli might play a role in the increase of peripheral blood B alpha cells in patients with IgA nephropathy.     

Increase of IgA-specific switch T cells in patients with IgA nephropathy.

Enumeration and functional analysis of CD4+ T cells with receptors for the Fc portion of IgA (i.e. T alpha 4 cells) in the peripheral blood of patients with IgA nephropathy, their relatives and age-matched controls were performed to elucidate polyclonal activation of IgA production in this disease. Enumeration of T alpha 4 cells was performed by a fluorescence activated cell sorter, and functional analysis was carried out by separation of T alpha 4 cells, and IgM-, IgA- and IgG-bearing lymphocytes using panning methods followed by cultures of these cells for 7 days with pokeweed mitogen. There was a significant increase in the amount of peripheral blood T alpha 4 cells in patients with IgA nephropathy and their relatives. T alpha 4 cells specifically enhanced the switch of IgM-bearing cells to IgA-bearing cells, and this switch activity was inhibited by addition of human myeloma IgA. It is suggested that T alpha 4 cells may be responsible for polyclonal activation of IgA production in IgA nephropathy.     

Subpopulations of T alpha cells in patients with IgA nephropathy: correlation between T alpha 4 cells and in vitro IgA production

T cells play important roles in the regulation of the immune system and are divided into subpopulations by various kinds of markers on the membrane surface. T cells with Fc-receptors for IgA are termed T alpha cells, and the properties of this cell population have been revealed in recent years. T alpha cells are increased in patients with IgA nephropathy and possess IgA specific helper activity. T alpha cells consist of two subpopulations, T alpha cells with OKT4 antigen (T alpha 4 cells) and with OKT8 antigen (T alpha 8 cells). To investigate the immunological aberrations in patients with IgA nephropathy, we detected immunoglobulin produced by peripheral blood lymphocytes and enumerated the numbers of T alpha cells (including both T alpha 4 and T alpha 8 cells). The numbers of T alpha 4 cells (but not T alpha 8 cells) and in vitro IgA production were increased in patients with IgA nephropathy (IgA nephropathy, mean 1.9%. Control, mean 0.8%. P = 0.0075). In addition, the numbers of T alpha 4 cells and the amount of IgA in the supernatant of lymphocyte cultures were positively correlated in these patients (P = 0.025. r = 0.3836). From the results in the present study, it was suggested that T alpha 4 cells might be related to immunological aberrations, such as an increase in IgA seen in patients with IgA nephropathy.     

Immunological studies in a familial IgA nephropathy.

The hypothesis that abnormalities of immune function might occur in healthy first degree relatives of two patients with a familial IgA nephropathy was tested. After 7 days of culture, pokeweed mitogen stimulated peripheral blood mononuclear cells from the two affected members with IgA nephropathy (father and older son), as well as two other healthy sons, produced significantly more polymeric IgA than the controls. The fact that only the two patients with IgA nephropathy presented high serum levels of polymeric IgA favours the idea that a defect in the clearance of this immunoglobulin might be an important step in the appearance of this nephropathy. All the healthy members of the family had a normal OKT4+/OKT8+ cell ratio and a normal concanavalin A generated IgA suppressor cell function in contrast with the abnormalities observed in the two affected members and the previous results in a large number of patients with IgA nephropathy. These data suggest that the primary cellular abnormality might reside in B cells, being the T cell alterations observed in patients a secondary or subsequent phenomenon. These results further support the existence of genetic bases for the susceptibility to this disease.     

Development of IgA nephropathy-like glomerulonephritis associated with Wiskott-Aldrich syndrome protein deficiency

Wiskott-Aldrich syndrome (WAS) is a rare X-linked disorder caused by mutations in the WAS gene. Glomerulonephritis is a frequent complication, however, histopathological data from affected patients is scarce because the thrombocytopenia that affects most patients is a contraindication to renal biopsies. We found that WASp-deficient mice develop proliferative glomerulonephritis reminiscent of human IgA nephropathy (IgAN). We examined whether increased aberrant IgA production is associated with the development of glomerulonephritis in WASp-deficient mice. Serum IgA and IgA production by splenic B cells was increased in WASp-deficient mice compared to wild-type (WT) mice. A lectin-binding study revealed a reduced ratio of sialylated and galactosylated IgA in the sera from old WASp-deficient mice. Circulating IgA-containing immune complexes showed significantly higher titers in WASp-deficient mice compared to WT mice. These results indicate that the increased IgA production and aberrant glycosylation of IgA may be critically involved in the pathogenesis of glomerulonephritis in WAS.     

IgA-dominant acute poststaphylococcal glomerulonephritis complicating diabetic nephropathy

Two pathological patterns of acute poststaphylococcal glomerulonephritis are well defined and include (1) an acute proliferative and exudative glomerulonephritis closely resembling classical acute poststreptococcal glomerulonephritis in patients with Staphylococcus aureus infection and (2) a membranoproliferative glomerulonephritis in patients with Staphylococcus epidermidis infection secondary to ventriculovascular shunts. In this study, we report a novel immunopathologic phenotype of immunoglobulin (Ig) A-dominant acute poststaphylococcal glomerulonephritis occurring in patients with underlying diabetic nephropathy. Five patients with type 2 diabetes presented with acute renal failure occurring after culture-positive staphylococcal infection. Renal biopsy disclosed an atypical pattern of acute endocapillary proliferative and exudative glomerulonephritis with intense deposits of IgA as the sole or dominant immunoglobulin, mimicking IgA nephropathy. The deposits were predominantly mesangial in distribution with few subepithelial humps. All five cases occurred superimposed on well-established diabetic nephropathy. Outcome was poor with irreversible renal failure in four of five (80%) cases. The possible pathophysiological basis of this atypical form of acute poststaphylococcal glomerulonephritis in diabetic patients is explored. Proper recognition of this entity is needed to avoid an erroneous diagnosis of IgA nephropathy, with corresponding therapeutic and prognostic implications.     

Familial selective IgA deficiency with circulating anti-IgA antibodies: a distinct group of patients?

Two families were investigated in which the mothers had selective IgA deficiency and circulating class-specific anti-IgA antibodies. Both gave birth to two children who were found to be IgA deficient. Three of these children developed anti-IgA antibodies before puberty. In vitro immunoglobulin production studies performed in the children of both families revealed an IgA B cell defect combined with IgA-specific excessive T suppressor function in all four. The mechanisms by which transplacental passage of maternal anti-IgA antibodies could have interfered with the developing IgA system in the offspring are discussed.     

Investigation on antibodies to human T cell leukemia virus type I in patients with primary glomerulonephritis

We investigated on antibodies to human T cell leukemia virus type I (anti HTLV-I) in 101 patients with primary glomerulonephritis in Kagoshima prefecture, an endemic area of HTLV-I in Japan. The positive rate in patients with primary glomerulonephritis was 17.8%, which was not significantly higher than in healthy residents 4741 persons of 11.9% in the same area. Classified by renal biopsy findings, the positive rate in patients with membranous nephropathy was 21.4% (9/42), minimal change nephrotic syndrome 14.3% (2/14), IgA nephropathy 15.4% (2/26), and others 15.8% (3/19) respectively, which were not significantly differed from that in healthy residents. Positivity of aged patients (60 years or over) in membranous nephropathy on the contrary was significantly higher than that in healthy residents (p less than 0.01). Further study is required to clarify the relationship between HTLV-I infection and glomerulonephritis.     

Disorders of regulatory T cells in patients with selective IgA deficiency and its relationship to associated autoimmune phenomena

In vitro lymphocyte function of 13 patients with selective IgA deficiency was studied. IgG, IgA and IgM secretion by pokeweed mitogen-stimulated peripheral blood lymphocytes from normal donors and IgA deficient patients was measured by an enzyme-linked immunosorbent assay. Addition of concanavalin A or hydrocortisone and co-cultures of B and T cell enriched populations from patients and normal donors, allowed us to investigate B cell Ig production and T cell regulatory abnormalities. IgA production by these patients' B cells was either absent or very low, as compared to their total Ig production, even in the presence of optimal T cell help. Several T cell immunoregulatory abnormalities were seen in different patients. A moderate increase in suppressor activity selective for IgA production was observed in some, but does not appear to play a major role in the pathogenesis of the IgA deficiency. In others, with associated autoimmune phenomena, a decrease in suppressor T cell function was found.     

Decreased suppressor T cell activity in patients with hepatic cirrhosis (HC).

Hypergammaglobulinaemia (HGG) is frequently found in patients with hepatic cirrhosis (HC). Using an assay system of in vitro PWM-stimulated immunoglobulin (Ig) production, the amounts of IgG, IgA, and IgM produced by peripheral blood lymphocytes (PBL) from 15 HBs Ag-negative patients with HC and from 16 age-matched healthy subjects were quantitated by radioimmunoassay. We found that PBL from patients with HC produced significantly greater amounts of IgG (P less than 0.05) but not IgA or IgM than did those from control subjects. This increased IgG production by PBL from patients with HC was attributed to enhanced T helper activity and not to enhanced B cell function. We also searched for defects in naturally occurring suppressor T cell activity which is sensitive to irradiation. Irradiation-induced enhancement for IgG production was significantly lower in patients with HC compared with age-matched control subjects (P less than 0.01). Similarly, we examined the effect of Con A-induced suppressor T cells on the in vitro PWM-stimulated IgG production by allogeneic PBL and observed the decrease of Con A-induced suppressor T cell activity in patients with HC (P = 0.01). We conclude, therefore, that the increased serum levels of Ig, particularly IgG in patients with HC may result from in part on the basis of depressed ability of naturally occurring suppressor T cells or Con A-induced suppressor T cells to suppress Ig production.     

Therapy of IgA Nephropathy

IgA nephropathy is the commonest form of glomerulonephritis worldwide, and is one of the major causes of terminal renal failure in most industrialised countries. It is defined by the dominance of IgA mesangial deposits in immunofluorescence studies. Corticosteroid-sensitive nephrosis lipoides (minimal change disease) with IgA deposits and superimposed crescentic glomerulonephritis are to be differentiated from primary IgA nephropathy (Berger's disease). In the latter, clinical manifestations are dominated by synpharyngitic macroscopic haematuria and permanent proteinuria. Terminal renal failure occurs in about 25% of patients after 10 years or more. Heavy proteinuria, hypertension, altered renal function and severe histological lesions at diagnosis are markers of poor prognosis. Primary IgA nephropathy is thought to be related to mesangial deposition of polymeric IgA1-containing immune complexes, owing to altered B cell responses to exogenous and endogenous antigens, together with hyperactivity of T helper type 1 and type 2 cells, both favoured by a genetic background. The 2 compartments of the IgA system (medullary and mucosal) may participate in the pathogenesis of the disease. Modulation of gut-associated lymphoid tissue and immune tonsillectomy are current lines of research. Although impressive results were obtained with an oligoantigenic diet, it is somewhat impractical. Pharmacological modulation of the mucosal immune response seems more promising. There is no proof that phenytoin, a drug which reduces bone marrow IgA synthesis, is beneficial. Emerging data suggest the potential of immune intervention in severely proteinuric patients before sclerotic lesions have occurred, using azathioprine and intravenous immunoglobulins. The benefit of early corticosteroid therapy is still unknown in both adults and children, and the efficiency of alkylating agents is unproven. The search for bacterial foci in primary IgA nephropathy is mandatory, as appropriate treatment may have a protective effect on renal function and help to improve or stabilise some patients. Slowing the progression of renal failure by a combination of ACE inhibitors, fish oil and, possibly, antiplatelet drugs is a promising therapeutic approach.