Defective reticuloendothelial system Fc-receptor function in systemic lupus erythematosus

Immune complex processing in patients with systemic lupus erythematosus. In vivo imaging and clearance studies

Abnormal processing of immune complexes (IC) may be important in the pathogenesis of systemic lupus erythematosus (SLE). The clearance of large soluble IC (comprising hepatitis B surface antigen (HBsAg)/anti-HBsAg) radiolabeled with 123I was examined in 12 normal subjects and 10 patients with SLE. IC localization was analyzed by static and dynamic gamma-scintigraphy. Initial IC clearance from blood was more rapid in patients (median t1/2 = 2.15 min) than normals (median t1/2 = 5.15 min) due to more rapid uptake in the liver. However, in the SLE group, up to 12% of complexes were released from the liver after 30-50 min. Splenic uptake of immune complexes was reduced in the patients and there was reduced ability to retain IC in this organ. Plasma complement levels and erythrocyte complement receptor type 1 numbers were reduced in the patients, resulting in defective opsonization of IC and reduced red cell binding in vivo. These observations support the hypothesis that IC handling is abnormal in SLE.

Treatment of severe thrombocytopenia in systemic lupus erythematosus with intravenous gammaglobulin

Three patients with lupus with severe auto-immune thrombocytopenia were treated with high doses of intravenous gammaglobulin. In the patient with active disease a prolonged but partial response with respect to platelet counts was observed. In the two other patients who had no disease activity other than thrombocytopenia at the time of intravenous gammaglobulin treatment a minor (and only transient) increase in platelet counts was seen after treatment. No change in the state of disease activity nor in the levels of antinuclear antibodies, circulating immune complexes, nor complement C3/4 was observed in these three patients after treatment with intravenous gammaglobulin.

Assessment of disease activity and impending flare in patients with systemic lupus erythematosus. Comparison of the use of complement split products and conventional measurements of complement

OBJECTIVE

To determine whether increased levels of the complement split products generated in the activation of the alternative or classical pathway accompany more severe disease activity in patients with systemic lupus erythematosus (SLE) and whether these measurements are useful in predicting flares of disease.

METHODS

Levels of Ba, Bb, SC5b-9, and C4d were measured in 380 plasma samples obtained from 86 SLE patients who were prospectively followed up for 15 months.

RESULTS

In the 20 patients who had inactive disease at the initiation of the study, the mean values of all of the complement split products at entry were within the normal range. In the 47 patients with stable or moderate disease activity, levels of Ba were significantly increased, while the mean values for Bb, SC5b-9, and C4d did not differ significantly from those in patients with inactive disease. The mean entry value of each analyte was highest in the group of 19 patients who had the most severe disease activity at initial evaluation. Traditional measurements of complement, i.e., C3, C4, and CH50, followed similar trends, but did not discriminate between the 3 groups of patients as well as did measurements of the split products. Analysis of the disease course in the patients with inactive or stable/moderate disease revealed that an elevated level of C4d had the most sensitivity with regard to subsequent flare, while an elevated Bb level had the highest specificity and the greatest predictive value.

CONCLUSION

These data suggest that elevated levels of complement split products, particularly products of alternative and terminal pathway activation, more accurately reflect disease activity than do conventional measurements of complement in SLE and may be useful in the prediction of impending disease flares.

In vivo clearance by the mononuclear phagocyte system in humans: an overview of methods and their interpretation

The mononuclear phagocyte system (MPS) is responsible for the elimination of foreign material, effete autologous material and immune complexes. To study the relationship between MPS function and human disease, several test substances have been developed, and used to determine the clearance capacity of the MPS in human subjects in vivo. These test substances and the multitude of factors that influence the elimination of these substances (and complicate the interpretation of the test results) are discussed. Use of these probes has provided important new insights, that may lead to the development of treatment modalities by which MPS function is modified in order to influence disease processes more effectively.

Phenotypic and functional similarities between 5-azacytidine-treated T cells and a T cell subset in patients with active systemic lupus erythematosus

OBJECTIVE

Antigen-specific CD4+ T cells treated with DNA methylation inhibitors become autoreactive, suggesting a novel mechanism for autoimmunity. To test whether this mechanism might be involved in systemic lupus erythematosus (SLE), phenotypic markers for the autoreactive cells were sought.

METHODS

Cloned normal T cells were treated with the DNA methylation inhibitor 5-azacytidine (5-azaC) and studied for altered gene expression. T cells from patients with active SLE were then studied for a similar change in gene expression, and cells expressing the marker were tested for autoreactivity.

RESULTS

5-azaC-treated normal T cells had increased CD11a (leukocyte function-associated antigen 1 alpha) expression relative to other membrane molecules. A T cell subset with similar CD11a expression was found in patients with active SLE. This subset contained cells that spontaneously lysed autologous macrophages, with a specificity similar to that of 5-azaC-treated cells.

A controlled trial of plasmapheresis therapy in severe lupus nephritis. The Lupus Nephritis Collaborative Study Group

BACKGROUND

The prognosis of patients with systemic lupus erythematosus who have glomerulonephritis is poor, despite treatment with immunosuppressive therapy. Plasmapheresis therapy has been used, but there have been few controlled clinical observations of its efficacy.

METHODS

We carried out a randomized, controlled trial comparing a standard-therapy regimen of prednisone and cyclophosphamide (standard therapy) with a regimen of standard therapy plus plasmapheresis in 86 patients with severe lupus nephritis in 14 medical centers. The patients underwent plasmapheresis three times weekly for four weeks. Drug therapy was standardized, with strict adherence to nine detailed medical-management protocols.

RESULTS

Forty-six patients received standard therapy, and 40 patients received standard therapy plus plasmapheresis. The mean follow-up was 136 weeks. Six patients (13 percent) in the standard-therapy group and eight patients (20 percent) in the plasmapheresis group died. Renal failure developed in 8 patients (17 percent) in the standard-therapy group, as compared with 10 (25 percent) in the plasmapheresis group. Thirty patients (35 percent) reached stopping points--14 (30 percent) in the standard-therapy group and 16 (40 percent) in the plasmapheresis group. A similar number of patients in each group had a decrease in both the serum creatinine concentration and urinary protein excretion to approximately normal values. Patients treated with plasmapheresis had a significantly more rapid reduction of serum concentrations of antibodies against double-stranded DNA and cryoglobulins.

CONCLUSIONS

Treatment with plasmapheresis plus a standard regimen of prednisone and cyclophosphamide therapy does not improve the clinical outcome in patients with systemic lupus erythematosus and severe nephritis, as compared with the standard regimen alone.

Universal occurrence of glomerular abnormalities in patients receiving liver transplants

We conducted a prospective study of renal histology and function in 18 consecutive nonalcoholic patients who underwent orthotopic liver transplantation (OLT). Despite well-preserved renal function, all patients had abnormal renal biopsies. Four patterns of glomerular injury were identified: minor glomerular abnormalities (eight patients), hepatic glomerulosclerosis (seven), membranoproliferative glomerulonephritis (one), and IgA nephropathy (one). In one patient there was insufficient tissue to allow classification. There was a trend toward lower plasma bilirubin and higher plasma albumin in patients with minor glomerular abnormalities than in the group of patients with more severe forms of glomerular injury (29 v 82 mumol/L, 35.5 v 30 g/L; P = 0.1, 0.1 greater than P greater than 0.05, respectively). Glomerular changes persisted in the three patients who died within 7 weeks post-OLT. IgM immunofluorescence was present in all biopsies and IgA in 11. IgM-containing circulating immune complexes occurred in five patients, suggesting a pathogenic role for IgM immune complex deposition. The significance of cirrhosis-associated glomerular abnormalities is not yet known. They may contribute to the hepatorenal syndrome and the renal dysfunction that occurs in up to 94% of patients post-OLT.

Autoimmunity, polyclonal B-cell activation and infection

It is widely believed that autoimmunity is an integral part of the immune system, and that genetic, immunologic, hormonal, environmental and other factors contribute to the pathogenesis of autoimmune disease. Thus, autoimmune disease may represent an abnormal expression of immune functions instead of loss of tolerance to self, and it can be organ specific or systemic in its manifestations. We review the various factors that contribute to the development of autoimmune disease; we also review the mechanisms of polyclonal B-cell activation, with emphasis on the role of infectious agents. We consider systemic lupus erythematosus in humans and in experimental animals as prototypic autoimmune disease, and we summarize data to indicate that polyclonal B-cell activation is central to the pathogenesis of systemic autoimmune disease. The effect of polyclonal B-cell activation, brought about by injections of a B-cell activator-lipopolysaccharide from Gram-negative bacteria-is sufficient to cause autoimmune disease in an immunologically normal host. In fact, autoimmune disease can be arrested if excessive polyclonal B-cell activation is suppressed; alternatively, autoimmune disease can be exacerbated if polyclonal B-cell activation is enhanced. We explore the mechanism of tissue injury when autoimmune disease is induced or exacerbated, and we consider the pathogenic roles of autoantibodies, immune complexes, complement, the blood cell carrier system, and the mononuclear phagocyte system. Although polyclonal B-cell activation may be the mechanism whereby various factors can cause or exacerbate systemic autoimmune disease, polyclonal B-cell activation may cause autoimmune disease on its own.

Defective Fc receptor-mediated clearance in patients with primary biliary cirrhosis

Fc receptor-mediated clearance of immunoglobulin G-coated autologous erythrocytes was studied in patients with primary biliary cirrhosis (n = 14), alcoholic liver cirrhosis (n = 5) and healthy reference individuals (n = 14). The mean half-life of the sensitized erythrocytes was significantly prolonged in patients with primary biliary cirrhosis (85 +/- 25 minutes; P less than 0.001) compared with the corresponding value in patients with alcoholic cirrhosis (16 +/- 2 minutes) and healthy reference individuals (20 +/- 5 minutes), respectively. No correlation between clearance rate and age, liver histopathology, or serum levels of bilirubin, aminotransferases, immunoglobulin G, immunoglobulin A, and Clq binding or C3-containing immune complexes was found. The results presented here indicate a profound disturbance of Fc receptor-mediated immune clearance function in patients with primary biliary cirrhosis.

An improved method to study complement receptor-mediated function of the fixed macrophage system in vivo

A method to coat unsensitized erythrocytes with fragments of C3 and C4 using autologous serum, in order to study complement receptor-dependent function of the fixed macrophage system, is presented. After incubation with serum under optimal conditions, at least 90% of the cells had C3b/iC3b deposited on the surface, with an average of 20 x 10(3) molecules per cell. Elimination of the coated cells by the fixed macrophage system was studied in 12 normal subjects. With a dose of 4.5 x 10(8) red cells injected, 75% of the cells were eliminated with a half-life of approximately 2.4 +/- 0.3 min (n = 7). In subjects receiving ten times more cells, there was a rapid decrease in the amount of C3-coated cells, reaching a nadir with 85% remaining for 4-6 min, after which there was a gradual release of cells for another 20 min (n = 5). In absolute numbers, 3 x 10(8) of labeled cells were eliminated regardless of the dose injected. The coating procedure presented here is simple, does not introduce heterologous blood components and makes it possible to control the amount and the degree of fragmentation of the C3 and C4 deposited on the erythrocyte surface.

The fate of aggregated immunoglobulin A injected in IgA nephropathy patients and healthy controls

Organ uptake of IgA-containing immunologically active material was studied in humans by intravenous (IV) injection of 131I-labeled heat-aggregated human secretory IgA (HAS-IgA) in nine patients affected by primary IgA nephropathy and 10 normal volunteers. Aggregated secretory IgA was found to be removed almost exclusively by the liver. The peak activity in liver was reached at 21.1 minutes (range, 18 to 26 minutes) in patients and 19 minutes (range, 14 to 22 minutes) in controls. The rate of increase of liver radioactivity was found to be significantly slower in patients (with a mean slope of 5.0; range, 3.4 to 7.1 v 7.6, 5.6 to 11.4; P less than 0.02). The mean liver to precordium ratio at the peak time was significantly lower in patients (mean value, 2.3; range, 1.9 to 3.1) compared with controls (mean value, 3.3; range, 2.4 to 4.0) (P less than 0.02). These data confirm the pivotal role of the liver in the removal of aggregated IgA in humans and the defective clearance capacity of this test probe in IgA nephropathy patients.

Uptake and degradation of soluble aggregates of IgG by monocytes of patients with rheumatoid arthritis: relation to disease activity

Monocytes from patients with rheumatoid arthritis (RA) and rheumatoid vasculitis have a diminished ability to degrade soluble complexes of aggregated IgG in the absence (mediated by Fc receptors) as well as in the presence of complement (C) (mediated by (Fc + C) receptors). To investigate whether a relation exists between the receptor mediated degradation of aggregated IgG by adherent monocytes and disease activity a longitudinal study was performed in 79 patients with RA and rheumatoid vasculitis over a period of 16 months. Adherent monocytes were incubated in vitro with 125I labelled IgG aggregates of restricted size in the absence or presence of fresh serum and the percentage of catabolised IgG aggregates was measured. Cross sectionally the degradation of aggregated IgG by monocytes, mediated by Fc and (Fc + C) receptors, correlated significantly with disease activity as scored by the Ritchie articular index, the presence of extra-articular features, and circulating immune complexes. A high number of Fc receptors on monocytes correlated with diminished degradation, whereas high numbers of complement receptors 1 and 3 correlated with enhanced degradation of aggregated IgG mediated by both Fc and (Fc + C) receptors. The degradation of aggregated IgG by monocytes did not correlate with disease activity in individual patients followed up longitudinally. When patient groups were formed according to the results of longitudinal studies, however, degradation of aggregated IgG mediated by Fc and (Fc + C) receptors was significantly decreased in patients with rheumatoid vasculitis and in patients with active RA in comparison with patients with inactive RA and healthy controls. Patients with active RA and rheumatoid vasculitis also expressed significantly more Fc receptors and less complement receptors on the monocytes than patients with inactive RA. Drug treatment did not correlate with receptor expression or the degradation of aggregated IgG by monocytes either in cross sectional or longitudinal studies. It is concluded that in RA disease activity is related to receptor expression and the degradation of soluble immune aggregates by monocytes.

Association of circulating receptor Fc gamma RIII-positive monocytes in AIDS patients with elevated levels of transforming growth factor-beta

Monocytes in the circulation of normal individuals express two receptors for the constant region of immunoglobulin, Fc gamma RI and Fc gamma RII. In contrast, we have observed that AIDS monocytes express significant levels of a third Fc gamma R, Fc gamma RIII (CD16), which is normally associated with activation or maturation of the monocyte population. By dual-fluorescence analysis using a monoclonal antibody specific for Fc gamma RIII (MAb 3G8), 38.5 +/- 3.2% of the LeuM3 (CD14)-positive monocytes in AIDS patients were CD16 positive as compared to 10.4 +/- 1.0% for healthy individuals (n = 29; P less than 0.005). Furthermore, AIDS monocytes expressed Fc gamma RIII-specific mRNA which is expressed minimally or not at all in control monocytes. As a recently identified inducer of Fc gamma RIII expression on blood monocytes, transforming growth factor-beta (TGF-beta) was found to be elevated in the serum and/or plasma of AIDS patients. Moreover, incubation of normal monocytes with AIDS serum or plasma induced CD16 expression which correlated with serum TGF-beta levels (r = 0.74, P less than 0.001) and was inhibited with a neutralizing antibody to TGF-beta. Thus, the increased CD16 expression on peripheral blood monocytes in AIDS patients may be the consequence of elevated circulating levels of the polypeptide hormone TGF-beta.

Elimination of soluble 123I-labeled aggregates of IgG in patients with systemic lupus erythematosus. Effect of serum IgG and numbers of erythrocyte complement receptor type 1

Using soluble 123I-labeled aggregates of human IgG (123I-AHIgG) as a probe, we examined the function of the mononuclear phagocyte system in 22 patients with systemic lupus erythematosus (SLE) and 12 healthy controls. In SLE patients, a decreased number of erythrocyte complement receptor type 1 was associated with less binding of 123I-AHIgG to erythrocytes and a faster initial rate of elimination of 123I-AHIgG (mean +/- SEM half-maximal clearance time 5.23 +/- 0.2 minutes, versus 6.58 +/- 0.2 minutes in the controls), with possible spillover of the material outside the mononuclear phagocyte system of the liver and spleen. However, multiple regression analysis showed that serum concentrations of IgG were the most important factor predicting the rate of 123I-AHIgG elimination. IgG concentration may thus reflect immune complex clearance, which in turn, would influence the inflammatory reaction, in SLE.

Molecular basis of IgG Fc receptor III defect in a patient with systemic lupus erythematosus

By flow cytometry analysis we could show a decreased expression of Fc gamma receptor type III (Fc gamma RIII) on granulocytes of a patient with systemic lupus erythematosus (SLE). Therefore, we constructed a leukocyte cDNA library from this patient with the aim of investigating this defect on the molecular level. Using an Fc gamma RIII cDNA probe we isolated 15 Fc gamma RIII cDNA clones, which were all characterized by sequencing. Our sequence data revealed that the patient was heterozygous for Fc gamma RIII (NA-1/NA-2). Only clone 5 (NA-2) was a full-length cDNA clone. In contrast to the wild-type Fc gamma RIII the signal sequence is mutated, lacking the hydrophobic region essential for co-translational transport across the endoplasmic reticulum membrane. The predicted transport defect leading to the lack of membrane expression could be confirmed by immunofluorescence staining after expression of this cDNA clone in BHK cells. The cDNA clones 6 and 8 (NA-1) lack the first 45 bp of the signal sequence, but considering the flow cytometry data the signal sequence must be functional allowing the membrane expression of this receptor allele. The part of the cDNA sequence of all isolated clones coding the mature Fc gamma RIII is identical to the wild-type sequence. Therefore, we conclude that the decreased expression of Fc gamma RIII on granulocytes of this SLE patient is due to the transport defect of one of the receptor alleles.

Effect of cyclophosphamide on the clearance of IgG-sensitized red cells in mice

The effects of cyclophosphamide (Cy) on the clearance of IgG-sensitized erythrocytes (EA) were examined. The results clearly indicate that Cy treatment enhances the capacity of the mononuclear phagocytic system to remove antibody-coated cells from the circulation in normal and decomplemented mice. The enhanced rate of clearance is the consequence of an increased uptake of EA by the liver and spleen. We explored the possibility that the enhancement of Fc receptor-mediated clearance might be an important effect to be taken into account in the search for a more effective therapy of immune complexes diseases.

LDL-mediated interaction of DNA and DNA-anti-DNA immune complexes with cell surface

The effect of low-density lipoprotein (LDL) on the binding of DNA and DNA-anti-DNA immune complexes to cultured human skin fibroblasts was examined. Using radioisotope analysis, ELISA and indirect immunofluorescent staining, a correlation between plasma membrane-bound DNA or DNA-anti-DNA immune complexes and cell-associated LDL was established. It was demonstrated that cytotoxicity and internalization of DNA-anti-DNA immune complexes may be LDL mediated. The data obtained suggest that the binding of the major part of DNA and immune complexes bound to surface of normal skin fibroblasts is due to the formation of a DNA-LDL-LDL receptor linkage. A possible role of LDL-containing immune complexes in the pathogenesis of systemic lupus erythematosus is discussed.

Fc gamma RII restriction fragment length polymorphism (RFLP): analysis in systemic lupus erythematosus and scleroderma and evidence of an alpha gene duplication

The characteristic finding of high levels of circulating immune complexes in patients with the autoimmune connective tissue diseases systemic lupus erythematosus (SLE) or scleroderma has raised the possibility that these patients may have a primary defect in immune complex clearance. The Fc receptor for IgG (Fc gamma R) plays a central role in the phagocytosis of antibody complexes. We have analysed Fc gamma R (type II) RFLPs identified in TaqI- and MspI-restricted genomic DNA and found that their distribution in SLE and scleroderma did not differ significantly from controls. Hybridization with specific regions of the Fc gamma RII cDNA clone indicate that part of the Fc gamma RII alpha locus is duplicated in some individuals. A further Fc gamma RII gene has recently been identified (Fc gamma RII alpha'). This gene shows greater than 95% homology with Fc gamma RII alpha and may thus be the candidate gene for the apparent alpha duplication seen in some individuals. It is possible that an individual may possess one, two, three or four TaqI Fc gamma RII alpha/alpha' alleles, correlating with incidence and numerical heterogeneity in Fc gamma RII alpha and alpha'. The physiological effects of this numerical heterogeneity remain to be investigated.

Functional asplenia in systemic lupus erythematosus

A patient with inactive systemic lupus erythematosus was successfully treated for pneumococcal sepsis complicated by disseminated intravascular coagulation, shock, renal failure, and functional asplenia. Functional asplenia was diagnosed from the total absence of uptake of intravenously administered 99mtechnetium-labeled sulfur colloid. Ten similar cases of functional asplenia occurring in patients with systemic lupus erythematosus were noted in a review of the literature. Six of these cases, including the current report, were complicated by pneumococcal (5) or salmonella (1) sepsis. The patient presented here had an excellent antibody response to pneumococcal vaccination. Spleen scan abnormalities fully reversed at 1 year. Although functional asplenia is a rare event in systemic lupus erythematosus, it appears to predispose to severe septic complications.

Prolonged circulation of immune complexes due to various altered immune functions contributes to nephritis in MRL/lpr mice

To gain some insight into the pathogenesis of proliferative lupus nephritis in MRL/lpr mice we investigated the kinetics of removal of immune complexes from the circulation, the carrier state of blood cells, the uptake of complexes by the mononuclear phagocyte system, and the localization of complexes in kidneys. In nephritic MRL/lpr mice challenged with a subsaturating dose of radiolabelled complexes (2.5 mg bovine serum albumin-anti-bovine serum albumin) liver uptake was profoundly decreased, removal of circulating complexes was delayed, and 12-h kidney localization of complexes was enhanced 7.3-fold, in comparison to control mice. The findings were not encumbered by differences in complement concentration and most likely are attributable to various altered immune functions: spontaneous polyclonal activation of B cells, enhanced production of endogenous immune complexes, delayed removal of complexes from the circulation, and decreased uptake of complexes by the mononuclear phagocyte system. In concert, such altered functions contribute to prolonged circulation of complexes to result in their enhanced deposition in the microcirculation.

Intravenous immunoglobulin therapy in systemic lupus erythematosus-associated thrombocytopenia

Seven patients with thrombocytopenia and systemic lupus erythematosus were treated with intravenous (IV) doses of human immunoglobulin to assess clinical response and to examine the mechanism of action of IV immunoglobulin in these patients. Five of 7 patients had a greater than 50% increase in their platelet counts. Four of these patients had a sustained benefit of at least 6 months duration. The initial effectiveness of IV immunoglobulin therapy was not dependent on the reduction of levels of circulating platelet-binding IgG or circulating immune complexes.

An abnormality of the gene that encodes neutrophil Fc receptor III in a patient with systemic lupus erythematosus

In the course of examining the structure and function of Fc receptors on peripheral blood cells of patients with systemic lupus erythematosus, we identified a patient whose neutrophils did not react with either monoclonal or polyclonal antibodies to Fc receptor III. However, neutrophils from the patient were comparable to neutrophils from healthy controls with respect to their expression of Fc receptor II, complement receptor 1, complement receptor 3, and the phosphatidylinositol-linked, complement regulatory protein, decay-accelerating factor. The abnormality of expression of Fc receptor III was limited to the patient's neutrophils (her natural killer cells reacted normally with anti-Fc receptor III antibodies), and was associated with abnormal recognition and binding of IgG-coated erythrocytes. Analysis of genomic DNA revealed evidence that failure of the patient's neutrophils to express Fc receptor III was most likely due to an abnormality of the gene that encodes this receptor.

Increased plasma fibronectin in patients with systemic lupus erythematosus

To add to our knowledge of collagen diseases, plasma fibronectin (FN) in patients with systemic lupus erythematosus (SLE) has been measured, and it was determined that the plasma FN value in those with SLE was 454 +/- 36 micrograms/ml, is significantly higher than the FN value in normal subjects (234 +/- 21 micrograms/ml) than that of patients with FN value of patients with active SLE was significantly higher (591 +/- 46 micrograms/ml) that of the patients with non-active SLE (287 +/- 31 micrograms/ml). The plasma FN value of SLE patients was also seen to be associated with the peripheral blood platelet count and with the dose level of the corticosteroid hormone administered to patients. In active SLE patients, it was similarly found that the plasma FN value had a significant correlation with the peripheral blood lymphocyte count and with the dose level of the corticosteroid hormone given to patients. Since the plasma FN value is known to be high in untreated SLE patients, it was felt that the increase of the FN value in SLE patients is not due to the effect of the corticosteroid but to the disease itself.

Beneficial effect of fibronectin administration on chronic nephritis in rats

We studied the effect of fibronectin (FN) on the course of chronic nephritis (induced by daily injections of ovalbumin) and on the clearance and catabolism of immune complexes in Wistar rats. Rats with chronic nephritis were treated with FN (2.5 mg/kg/48 hours) for 15 days after proteinuria was first detected. In rats with untreated nephritis, urinary protein levels increased from 40 +/- 22 mg/day (mean +/- SD) to 339 +/- 68 mg/day during the 15 days of the study (P less than 0.0005). This statistically significant increase was not observed in rats treated with FN (mean +/- SD 58 +/- 46 mg/day to 124 +/- 112 mg/day). Rats treated with FN showed a higher total serum protein level than did the untreated animals (mean +/- SD 6.4 +/- 0.3 gm/dl versus 5.1 +/- 0.5 gm/dl; P less than 0.0125), as well as a significant reduction in mesangial and glomerular basement membrane deposits. Untreated nephritic rats demonstrated delayed plasma clearance of 125I-labeled aggregated IgG (plasma half-life [T1/2] 3.03 +/- 0.6 minutes) and less catabolism of these aggregates at 30 minutes (mean +/- SD 15 +/- 1.7%) than did the normal rats (T1/2 1.5 +/- 0.2 minutes, 22 +/- 2.8%, respectively; P less than 0.0005). Both parameters were within normal limits in the FN-treated rats (T1/2 1.6 +/- 0.4 minutes, 22 +/- 6%, respectively). In vitro, FN induced a significant increase in aggregated IgG catabolism by Kupffer cells and peritoneal macrophages from normal rats. These results show that FN reduces the proteinuria and histologic lesions of chronic nephritis in rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Fc gamma receptor III on human neutrophils. Allelic variants have functionally distinct capacities

As a model system to explore the functional consequences of structural variants of human Fc gamma receptors (Fc gamma R), we have investigated Fc gamma R-mediated phagocytosis in relation to the NA1-NA2 polymorphism of Fc gamma RIII (CD16) on neutrophils (Fc gamma RIIIPMN). The neutrophil-specific NA antigen system is a biallelic polymorphism with codominant expression demonstrating a gene dose effect with the anti-NA1 MAb CLB-gran 11 in a large donor population. To explore the impact of this allelic variation of Fc gamma RIIIPMN on phagocytosis, we used two Fc gamma RIII-dependent probes, IgG-sensitized erythrocytes (EA) and concanavalin. A-treated erythrocytes (E-ConA). Comparison of Fc gamma R-mediated phagocytosis by PMN from NA1 subjects and from NA2 subjects showed lower levels of phagocytosis of both probes by the NA2 individuals. The difference was most pronounced with lightly opsonized EA: at the lowest level of sensitization the phagocytic index was 72% lower for NA2 donors, whereas at the highest level of sensitization it was 21% lower (P less than 0.003). Blockade of Fc gamma RII with MAb IV.3 Fab amplified by threefold the difference between NA1 and NA2 donors. NA1 and NA2 individuals had identical phagocytic capacities for the non-Fc gamma RIII probes, serum-treated and heat-treated zymosan. These individuals did not show differential quantitative cell surface expression of Fc gamma RIIIPMN measured by a panel of anti-CD16 MAb (3G8, CLB FcR-gran 1, VEP13, BW209/2) and by Scatchard analysis of 125I-IgG dimer binding. The difference in Fc gamma R-mediated phagocytosis was not explicable on the basis of differential collaboration of Fc gamma RIIIPMN alleles with Fc gamma RII, since (a) the difference in phagocytic capacity between NA1 and NA2 individuals was readily apparent with the E-ConA probe (which is independent of Fc gamma RII) and (b) the difference in phagocytosis of EA was magnified by Fc gamma RII blockade. The demonstration that allelic polymorphisms in Fc gamma R can have significant consequences for physiological functions implies that within the structural complexity of human Fc gamma Rs, including both allelic forms and cell type-specific isoforms, there will be differences in quantitative, and perhaps qualitative, function with potential importance for disease processes.

Impaired function of macrophage Fc gamma receptors in end-stage renal disease

Infection is a frequent complication in patients undergoing hemodialysis for end-stage renal disease and is the primary cause of mortality among such patients. Macrophages are important in host defense against infection largely because their Fc gamma receptors recognize antibody-coated bacteria. We therefore studied macrophage Fc gamma-receptor function in vivo and in vitro in 56 patients with end-stage renal disease who were on hemodialysis and in 20 healthy volunteers. The clearance of IgG-coated (sensitized) autologous red cells was decreased in 53 patients. The inhibition of clearance in the 56 patients was 52 +/- 3 percent at 1 hour, 41 +/- 5 percent at 1 1/2 hours, and 29 +/- 5 percent at 2 hours (P less than 0.001). The clearance of unsensitized erythrocytes and heat-altered autologous erythrocytes was normal. The impairment of clearance was not correlated with age, sex, nutritional status, HLA haplotype, or the presence of circulating immune complexes. The recognition of these IgG-sensitized red cells in vitro by Fc gamma RI (an Fc gamma-receptor protein that binds monomeric IgG) on blood monocytes from the patients was also significantly decreased (P less than 0.001) but was partially improved by hemodialysis. Nine patients had severe infections during a two-year follow-up period. The clearance of IgG-coated cells in these patients (half-time, 12.9 +/- 1.7 hours) was significantly impaired, as compared with that in the 47 patients without severe infections (half-time, 4.4 +/- 1.8 hours; P less than 0.001). We conclude that macrophage Fc gamma-receptor function is impaired in patients with end-stage renal disease who are undergoing hemodialysis, and that this impairment probably contributes to the observed immunodepression and high prevalence of infection among such patients.

Immune complex-mediated inhibition of lymphocyte Fc-gamma receptors in the plasma of patients with type 1 (insulin-dependent) diabetes mellitus: association with anti-ssDNA antibodies

Sera of 43 patients with type 1 (insulin-dependent) diabetes and from 42 normal subjects were examined for the presence of Fc-gamma receptor-blocking IgG immune complexes, detected by EA rosette inhibition, and for the presence of anti-ssDNA antibodies by ELISA. Forty-four percent of diabetic patients had levels of inhibition above the upper limit of normality in comparison to 7% of normal controls. Anti-ssDNA antibodies were found in the sera of 14 out of 43 diabetic patients. Ten out of 14 anti-ssDNA positive patients (71.5%) had inhibition levels above the upper limit of normality in comparison to 9 out of 29 (31%) of the anti-ssDNA negative population. The difference was statistically significant (P less than 0.005). Levels of EA rosette inhibition were found to be high in patients with duration of diabetes of less than 2 years and correlated with high prevalence of anti-ssDNA antibodies. The percentage of EA rosette inhibition was found not to correlate with the levels of C1q-binding immune complexes, suggesting that immune complexes detected by EA rosette inhibition may belong to a pool of noncomplement-fixing immune complexes. The possible role of immune complexes with autoantibodies anti-ssDNA in the mechanism triggering and perpetuating autoimmune phenomena in diabetes is discussed.

Mechanism of localization of immune complexes in NZB/W mice with early nephritis

We investigated the pathogenesis of mesangial proliferative lupus nephritis in NZB/W mice under conditions that allowed us to examine removal of immune complexes from the circulation, uptake by the mononuclear phagocyte system, and localization in kidney tissue. These studies were performed at a time when variables such as the quantity of endogenous immune complexes, complement concentration, and carrier state of blood cells (platelets) were controlled. NZB/W mice and C57BL/6 (control) mice showed comparable kinetics for removal of a subsaturating dose of immune complexes (2.5 mg bovine serum albumin-antibovine serum albumin) from the circulation; additionally, the liver uptake and kidney localization of these immune complexes were comparable between NZB/W and control mice. The localization of immune complexes in the glomerular mesangium of NZB/W mice could not be attributed to enhanced production of endogenous immune complexes, to decreased removal of immune complexes from the circulation, to impaired uptake by the liver, or to complement concentration and carrier state of blood cells. It appears, by exclusion, that mesangial deposits of immunoreactants in early lupus nephritis may result from interaction of antibodies with antigens in mesangia.

Plasmapheresis: technique and complications

Plasmapheresis has been used in an increasing number of diverse conditions over the past 15 years, and patients on intensive care units are sometimes so treated. This article reviews the principles, different techniques and refinements available, including the more specific methods of antibody removal, such as immunoadsorption. The vascular access, anticoagulation, choice of fluid replacement and monitoring requirements are discussed. The reported possible complications of plasmapheresis, relating both to the practical aspects of the procedure and to the effects of plasma removal and the replacement fluids, are reviewed.

Nuclear imaging and the assessment of human Fc receptor function: studies in systemic lupus erythematosus

In vivo immune clearance of immunoglobulin G sensitized autologous erythrocytes (rbc) was studied in nine patients who fulfilled American Rheumatism Association (ARA) criteria for systemic lupus erythematosus (SLE). Opsonized rbc were radiolabelled with technetium 99. The rate of radioactive blood clearance was measured, as was organ-specific radioactive uptake utilizing area-of-interest (AOI) measurements in a computerized scintigraphic imaging system. It was shown that dynamic quantitation of an AOI corresponding to the heart generated time-activity curves which approximated blood-clearance curves. Calculation of first order clearance (min per 50% decrease in counts) showed a highly significant correlation between rates derived from heart AOI curves and those derived from blood-clearance curves (r = 0.9483, P = 0.0003). Clearance curves showed a monoexponential slope in most patients. Further exploration of organ-specific AOI curves showed that percent splenic uptake and the nature of the splenic uptake curves varied between patients. These studies point toward a variable splenic role in Fc receptor function for SLE patients and further demonstrate the utility of nuclear imaging in studying immune clearance.

Circulating monocyte (macrophage)-specific antibodies in patients with autoimmune thyroid diseases

We investigated the presence of circulating monocyte-specific antibodies (monocytotoxic activities) by a complement-dependent cytotoxicity test and the relations between these monocytotoxic activities and other immunological indices in patients with autoimmune thyroid diseases. Antibodies reactive for monocytes (macrophages) were found in the sera from patients with autoimmune thyroid diseases. These antibodies were present in both IgG and IgM fractions and specific for monocytes since they were absorbed by monocytes but not by lymphocytes or granulocytes; furthermore, lymphocytotoxic and granulocytotoxic activities were not changed after the absorption of the sample sera by monocytes. Also, these antibodies did not have cross-reactivity to thyroid-specific antigens demonstrated by absorption tests and their specificity was different from anti HLA-DR antibody demonstrated by a flow cytofluorometric analysis. Monocyte-specific antibodies are reactive for autologous monocytes as well as allogenic monocytes. Patients who had positive monocytotoxic activities had high levels of TSH receptor antibodies (TRAb) and antimicrosomal antibodies in Graves' disease, and monocytotoxic activities were significantly correlated with the levels of TRAb in Graves' disease. These results suggest that the monocyte-specific antibodies (monocytotoxic activities) were significantly correlated with the immunological activities in Graves' disease.

Clinical relapse in systemic lupus erythematosus: correlation with antecedent elevation of urinary free light-chain immunoglobulin

This paper reports preliminary evidence suggesting that measurements of free light-chain Ig (FLIg) in urine may represent quantitative markers of in vivo polyclonal B-cell activation. Thus, longitudinal levels of urinary FLIg in patients with systemic lupus erythematosus (SLE) may be used to track or monitor the in vivo immunopathologic B-cell activity of SLE and be helpful in predicting a disease relapse. Our findings showed that dramatic rises in urinary FLIg occurred during asymptomatic intervals that preceded by 4-8 weeks the first symptomatic signs of acute SLE relapse. These results suggest that a sizable lead time may exist between the occurrence of immunopathologic B-cell stimulation and the resultant symptoms and tissue damage of immune complex-induced acute inflammation. In these studies the measurement of urinary FLIg was accomplished by an indirect method using ng-sensitive radioimmunoassays (RIAs) that measured isotypic IgG, IgA, IgM, total kappa-Ig, and total lambda-Ig. As a control for the assessment of renal tubular function and the excretion of low molecular weight proteins in SLE patients, longitudinal measurements of beta-2-microglobulin (B2M) and lysozyme were made using a novel solid-phase 3H-biotin RIA technique.

The treatment of lupus nephritis

The literature on the treatment of lupus nephritis is scattered, much of it in rheumatological rather than nephrological journals. Whatever our ignorance of the nature and genesis of lupus nephritis, under empirical treatment the prognosis, especially for severe forms, has improved dramatically during the past 20 years. For severe lupus nephritis, the evidence that the addition of cytotoxic agents to corticosteroids improves outcome is now secure, and discussion centres mainly on which drug to use and by what route. Intravenous methylprednisolone is at least as effective as high-dose tapering oral therapy for initial treatment, and carries fewer side-effects. The role of plasma exchange in lupus remains undefined: it may have a role in the treatment of cerebral manifestations or otherwise resistant patients, but controlled trials have failed to show benefit. Future developments will probably centre around the use of specific monoclonal antibodies which target specific groups and subgroups of cells, "humanised" by the splicing of human Fc piece to rodent (fab)2, perhaps bearing toxins. To use these agents to best advantage, however, we will have to understand better than we do today the nature of the cellular defects in the immune response which underlie the lupus syndrome.

High-dose, pulse intravenous methylprednisolone enhances Fc gamma receptor-mediated mononuclear phagocyte function in systemic lupus erythematosus

The benefit of high-dose, pulse intravenous methylprednisolone (IVMP) for some patients with active lupus nephritis would appear paradoxical, since active nephritis is associated with profound abnormalities in Fc gamma receptor function, and several studies have demonstrated that glucocorticoids decrease monocyte Fc gamma receptor expression and phagocytic function. To resolve this paradox, we investigated the possibility that pulse IVMP might enhance monocyte Fc gamma receptor function in patients with systemic lupus erythematosus (SLE). Circulating immune complex (CIC) levels, Fc gamma receptor-mediated clearance, and Fc gamma receptor-dependent monocyte function were analyzed in 23 SLE patients before and after pulse IVMP (1 gm daily for 3 days). A biphasic response in CIC levels, determined by a staphylococcal protein A binding assay, was observed. Initially, CIC levels increased within 2-4 hours after the first dose of pulse IVMP and then decreased by 50% within 24-48 hours after the completion of therapy. Fc gamma receptor-mediated binding and phagocytosis of IgG-sensitized erythrocytes (EA) by monocytes in vitro were significantly enhanced 24 hours after the final dose of pulse IVMP (pre-IVMP versus post-IVMP 43 +/- 14% versus 53 +/- 12% EA rosettes, P less than 0.01; 3.00 +/- 1.04 versus 3.99 +/- 1.30 EA ingested/monocyte, P less than 0.01). In contrast, there was no change in the phagocytosis of an Fc gamma receptor-independent probe, neuraminidase-treated erythrocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

The polymorphic Fc gamma receptor II gene maps to human chromosome 1q

Human receptors for IgG (Fc gamma R) play important roles in the immune response. Expression of the human Fc gamma RII gene may be relevant in immune complex related disorders such as systemic lupus erythematosus and Sjogren's syndrome. We have used spot blot analysis of dual laser-sorted human chromosomes to localize the Fc gamma RII gene to human chromosome 1. Spot blot analysis of sorted derivative chromosomes sublocalized the gene to the chromosome 1 long arm (1q12----q25.1). This subchromosomal localization involved reassigning a reciprocal chromosome translocation breakpoint. We also identified Xmn I and Taq I Fc gamma RII polymorphic restriction sites that arose before the races diverged. These common Xmn I and Taq I polymorphisms are predicted to be informative for segregation analysis with human diseases in 85% of all matings.

Membranoproliferative glomerulonephritis in a patient with congenital deficiency of the third component of complement: effect of treatment with plasma

A 21-year-old woman with a known congenital complement component 3 (C3) deficiency developed membranoproliferative glomerulonephritis. The kidney biopsy exhibited deposits of immunoglobulins and complement components despite the C3 deficiency. The administration of fresh frozen plasma was without therapeutic benefit. Corticosteroid treatment was followed by an improvement in kidney function.

Characterization of polymorphic forms of Fc receptor III on human neutrophils

We characterized Fc receptor III (FcR III) on human neutrophils and found it to be heavily glycosylated and polymorphic. In some individuals, FcR III that had been digested with N-glycanase appeared after SDS-PAGE under reducing conditions as two bands with apparent molecular masses of 33 and 29 kD. In other individuals, N-glycanase-treated FcR III appeared as a single band with an Mr of either 33 or 29 kD. After SDS-PAGE of N-glycanase-treated FcR III under nonreducing conditions, the apparent Mr of each structural type was decreased, suggesting the presence of intramolecular disulfide bonds. Digestion of the 33-kD band and the 29-kD band with Staphylococcus aureus V8 protease yielded similar, but not identical, peptide maps. Thus, at least two polymorphic forms of FcR III are expressed on human neutrophils. The structural polymorphism of neutrophil FcR III correlated with previously described antigenic polymorphisms detected by monoclonal antibody Gran 11 and by alloantisera which recognize epitopes of the biallelic, neutrophil antigen (NA) system. Individuals whose neutrophils expressed the two-band structural type of FcR III were NA1NA2 heterozygotes. Individuals whose neutrophils expressed the single 33-kD band structural type were NA2NA2 homozygotes, and individuals whose neutrophils expressed the single 29-kD band structural type were NA1NA1 homozygotes. These findings indicate that antigenic and structural polymorphisms of human neutrophil FcR III are related and can be accounted for by differences at the level of primary protein structure.

Dysfunction of the mononuclear phagocytic system in sepsis

An in vivo study has been undertaken of the Fc(IgG) receptor-mediated phagocytic capacity of macrophages (clearance of anti-rhesus D-coated-51 Cr-labelled autologous erythrocytes, expressed as half-lives) in 15 cases of sepsis to establish its behaviour and correlate this function to levels of circulating immune complexes (anti-Clq-nephelometry). Five patients with low activity (2261 +/- 859 minutes) developed septic shock; the other ten showed high activity (5.8 +/- 1.5 minutes) and did not develop septic shock. Differences from the control group (30 +/- 12 minutes) were found (p less than 0.001). Receptor activity was related to the presence of circulating immune complexes (p less than or equal to 0.001; delta = 0.862) but not to age, sex, or the presence/absence of splenomegaly during the illness. Eight patients responded favourably; seven patients died; but the receptor activity was not related to this. During sepsis it is possible to find higher Fc(IgG) receptor-mediated phagocytic capacity of macrophages. Excessive formation of circulating immune complexes has a negative influence on Fc(IgG) receptor-mediated phagocytosis. This activity of macrophages, measured at the start of the sepsis, was not associated with the final outcome of the patients' illness (cure or death).

Interaction of human IgG chimeric antibodies with the human FcRI and FcRII receptors: requirements for antibody-mediated host cell-target cell interaction

Chimeric monoclonal antibodies (McAb), specific for the hapten 5-iodo-4-hydroxy-3-nitrophenacetyl (NIP), expressing human IgG1, IgG2, IgG3 and IgG4 subclass constant domains, have been examined for their ability to interact with the human FcRII receptor. Human red blood cells (RBC) sensitized by each of these McAbs have been assayed for their ability to form rosettes with the human histiocytic lymphoma U937 cell line, human B cell line Daudi and erythroblastoid K562 cell line. IgG1 and IgG3 sensitized RBC formed significant rosettes with the FcR- and FcRII+ Daudi and K562 cell lines, the percentage of cells forming rosettes being directly proportional to the degree of sensitization of the RBC. Bromelin treating Daudi cells did not alter this pattern of reactivity, whereas bromelin treated FcRI+ and FcRII+ U937 cells formed significant resettes with IgG1, IgG3 and IgG4 sensitized RBC, demonstrating a difference in the IgG subclass specificity between human FcRI and FcRII. Murine IgG2b anti-NIP sensitized RBC did not form rosettes with any cell line tested; however, RBC sensitized by some members of a panel of murine IgG1 McAb, specific for the glycophorin A molecule, were able to form rosettes with Daudi, U937 and K562 cells. This interaction was enhanced by bromelin treating the Daudi or U937 cells and can be correlated to the disposition of the epitopes recognized, relative to the target cell membrane, those McAbs recognizing epitopes furthest from the RBC surface being most effective in interacting with FcRII. The data are interpreted in terms of a simple model for antibody-mediated cell--cell interaction.

Pathogenic subsets of antibodies to DNA

Among the autoantibodies that are known to play a role in the pathogenesis of autoimmune diseases, antibodies to DNA (anti-DNA) have been the subject of much study. Several interesting observations have resulted. The ability to make antibodies that bind DNA is not abnormal. Normal mice and humans can produce antibodies that bind DNA. On the other hand, large quantities of antibodies to DNA are found in the sera of patients with systemic lupus erythematosus (SLE), and complement-fixing antibodies to double-stranded (ds) DNA cause some of the tissue lesions, especially glomerulonephritis (GN). Why, then, do some individuals make anti-DNA that deposits in glomeruli, skin, and other tissue, resulting in organ damage? It is likely that disease results from a combination of several factors--ability to make pathogenic antibody subsets, inability to downregulate those subsets, and "tissue susceptibility" to injury from those antibodies and their immune complexes. This chapter will focus on the characteristics of pathogenic antibody subsets and their regulation.

Circulating immune complexes after splenectomy

Circulating immune complexes were evaluated in 25 patients (age range 10 to 46 years) who had undergone splenectomy for non-malignant conditions by studying a polyethylene glycol insoluble serum fraction. Although the extent of binding to Clq was within normal limits, these patients had increased concentrations of factor B in the immune complex serum fraction. These findings indicate that an unusual type of circulating immune complex may be detected after splenectomy, suggesting a possible role for the spleen in the removal of circulating immune complexes.

Immune complex assays: diagnostic and clinical application

The presence of circulating immune complexes have been described in many different human disease states but the significance of their presence has always been a subject for debate. Improvements in the methods of detecting immune complexes have demonstrated a wide degree of heterogeneity, which accounts for the difficulty in obtaining accurate and reproducible measurements, even in the same individual. Techniques for isolating individual complexes, characterizing their pathophysiological properties, and biochemically analyzing the nature of the complexed antigen are now being used to provide data that is helping to clarify the role of immune complexes in the pathogenesis of disease. In addition, such studies are also providing data which is proving that immune complexes have a potential role in immune regulation.

Immunogenetics of SLE and primary Sjögren's syndrome

SLE is a syndrome defined by clinical criteria and by the presence of autoantibodies reactive with nucleic acids and proteins concerned with transcription and translation. Breeding experiments in mice have illustrated the enormous genetic heterogeneity of this syndrome, of which the final common pathway is a widespread immune complex disease. The causes of SLE in humans are likely to be equally multifactorial. Family studies have demonstrated that genetic factors exist, but each factor appears to be a relatively weak disease-susceptibility gene. The major exceptions to this are the very rare complete deficiencies of classical pathway complement components, which are almost invariably accompanied by the development of SLE. Observations of these patients have led to the formulation of hypotheses relating complement and its receptor, CR1, to the defective removal of immune complexes from the circulation.

Juvenile rheumatoid arthritis. Monocyte dysfunction in selected patients

The in vitro parameters of cell-mediated immunity were studied in 20 children with an established diagnosis of Juvenile rheumatoid arthritis (JRA) (age range 4-15 years) and 23 age- and sex-matched healthy children. (No attempt was made to correlate the observed changes with clinical course or treatment). We are not certain, at this time, of clinical relevancy or the generalizability of the findings. The normal level of T-lymphocytes (CD3+) and normal proportions of CD4+ and CD8+ lymphocytes were seen in children with JRA. The in vitro response of lymphocytes to T-cell mitogen phytohemagglutinin (PHA) also was normal. The suppressor activity of JRA monocytes was essentially the same as controls. In contrast, monocytes from patients with JRA showed the following: decreased expression of receptors for Fc part of IgG immunoglobulin (FcR), diminished nitro blue tetrazolium (NBT) reduction activity, and depressed expression of Ia.7 major histocompatibility complex (MHC) class II determinants. This indicates that certain monocyte functions in selected patients with a variety of manifestations of JRA are depressed.

Treatment of murine lupus with monoclonal antibody to L3T4. I. Effects on the distribution and function of lymphocyte subsets and on the histopathology of autoimmune disease

Monoclonal antibodies (MoAb) to L3T4 have been used successfully to suppress autoimmunity in murine models for several human autoimmune diseases. To clarify the immunologic and clinical consequences of treatment with anti-L3T4, we examined the effects of chronic administration of anti-L3T4 on the composition of lymphoid organs, the function of lymphocytes, and the histopathology of autoimmune disease in lupus-prone NZB/NZW F1 (B/W) mice. Weekly treatment with anti-L3T4 (2 mg/mouse) from age 5 to 8 months depleted L3T4+ cells from the spleen and lymph nodes, and prevented the development of splenomegaly and lymphadenopathy. The MoAb bound to target cells in the thymus and modulated their expression of the L3T4 antigen but, in contrast to its effect in extrathymic sites, anti-L3T4 did not deplete the target population from the thymus. In fact, after 3 months of therapy, mice that had been treated with anti-L3T4 had much larger thymuses than control mice that had been treated with saline, suggesting that treatment with anti-L3T4 prevented the thymic atrophy that occurs spontaneously in murine lupus. Despite depleting L3T4+ cells from the spleen, treatment with anti-L3T4 did not diminish the response of splenic lymphocytes to T and B cell mitogens, and it augmented splenic natural killer (NK) cell activity. Finally, treatment with anti-L3T4 decreased the diverse histopathologic manifestations of murine lupus. It dramatically reduced glomerular immunoglobulin and complement deposition and diminished lymphocytic infiltration and vasculitis in the kidneys. Treatment also reduced extrarenal immunopathology, including focal hepatitis and salivary gland infiltration. These observations have implications regarding the use of CD4 MoAb in people with autoimmune diseases.

Reticuloendothelial clearance in cystic fibrosis and other inflammatory lung diseases

To examine the possible pathophysiologic role of circulating immune complexes in patients with cystic fibrosis and other inflammatory lung diseases, we studied the reticuloendothelial clearance of IgG-sensitized autologous erythrocytes in 15 patients with cystic fibrosis, 6 with chronic obstructive lung disease not related to cystic fibrosis, 7 with immunodeficiencies, 5 with systemic lupus erythematosus, 4 who had previously undergone a splenectomy, and 10 normal subjects. Patients with chronic inflammation and recurrent infections (i.e., those with cystic fibrosis, chronic obstructive lung disease, and immunodeficiencies) had significantly faster clearance rates (P less than 0.05, less than 0.01, and less than 0.005, respectively) than normal subjects. In contrast, patients with systemic lupus erythematosus (a classic immune complex-mediated disease) and those who had undergone a splenectomy had delayed clearance. The accelerated reticuloendothelial clearance in patients with chronic inflammatory pulmonary disease associated with cystic fibrosis was similar to that observed in stimulated laboratory animals. The rapid clearance rate may account for the rareness of septicemia in such patients despite chronic, persistent local bacterial infection.