Aggregated human immunoglobulin G stabilized by albumin: a standard for immune complex detection

Diagnostic strategy for the assessment of rheumatoid vasculitis

OBJECTIVE

To determine the clinical features associated with histologically proven rheumatoid vasculitis (HRV) and the additional diagnostic value of serological markers in an inception cohort of 81 patients with rheumatoid arthritis (RA) suspected of RV.

METHODS

The presence and number of recently developed extra-articular manifestations (EAMs) and a weighted EAM score, as well as the levels of serological markers, were compared between 31 patients with RA with histologically proven vasculitis and 50 patients with RA in whom vasculitis could not be documented histologically. The following markers were evaluated: circulating immune complexes, complement components C3 and C4, class-specific rheumatoid factors (IgM RF, IgG RF, IgA RF), antineutrophil cytoplasmic antibodies, antinuclear antibodies, antiendothelial antibodies, circulating intercellular adhesion molecule-1 and -3, circulating vascular cell adhesion molecule and E-selectin, cellular fibronectin, von Willebrand factor antigen, and C reactive protein. The diagnostic value of these markers, in addition to the clinical features, was evaluated with logistic regression analysis.

RESULTS

Peripheral neuropathy or purpura/petechiae, or both, were the most important clinical features to discriminate patients with RA with and without histologically proven RV. The presence of a high number of EAMs and a higher weighted EAM score in patients with RA suspected of vasculitis were also associated with an increased probability of histologically proven RV. After adjustment for EAMs, only the combination of an increased serum IgA RF level and a decreased serum C3 level appeared to make an additional contribution to the diagnosis histologically proven RV. Evidence of systemic vasculitis was found in a muscle biopsy of the rectus femoris in 9/14 (64%) patients with vasculitis with neuropathy and in 3/11 (27%) patients with purpura/petechiae and vasculitis of the skin.

CONCLUSIONS

In the diagnostic process of RV the presence of peripheral neuropathy and/or purpura/petechiae or a high weighted EAM score will increase the probability of histologically proven RV. Of the circulating factors previously suggested to be markers for RV only IgA RF and C3 further increase the probability of histologically proven RV and may be useful to guide diagnostic decisions.

Predictive value of IgG autoantibodies against C1q for nephritis in systemic lupus erythematosus

OBJECTIVES

Antibodies against C1q (C1qAb) have been demonstrated in the serum of patients with several immune complex diseases. Patients, particularly those with lupus nephritis, were found to have increased serum titres of IgG C1qAb in a cross-sectional analysis. In the present prospective study correlations were sought between serum titres of IgG C1qAb and clinical as well as laboratory parameters of disease activity in patients with systemic lupus erythematosus (SLE).

METHODS

Titres of IgG C1qAb in the serum of 68 SLE patients were measured serially during a three year period. At the same time clinical and laboratory parameters of disease activity were assessed.

RESULTS

Increased titres of IgG C1qAb were found in the serum of 56% of SLE patients during the study. Significant correlations were found between increased titres of IgG C1qAb and renal involvement. Clinical signs of renal involvement were found to be associated with significant increases of serum titres of IgG C1qAb in the six months preceding this appearance. Fifty per cent of the increases in serum titres of IgG C1qAb were followed by the development of renal involvement. Elevated serum titres of IgG C1qAb were especially related to proliferative forms of glomerulonephritis. Furthermore, significant correlations were found between serum titres of IgG C1qAb and serum levels of immune complexes, levels of complement components, and titres of antibodies to DNA.

CONCLUSIONS

The results suggest that IgG C1qAb play a pathogenic role in the development of lupus nephritis and that serial measurement of serum titres of IgG C1qAb is useful in the management of SLE patients.

Stimulation of the intracellular killing of Staphylococcus aureus by human monocytes mediated by Fc gamma receptors I and II

Previous studies have shown that intracellular killing of bacteria by monocytes is stimulated by interaction between IgG and Fc gamma receptors (Fc gamma R) in the membrane of these cells. In the present study anti-Fc gamma R monoclonal antibodies (mAb) were used to investigate the relative contributions of the various classes of Fc gamma R to the intracellular killing of Staphylococcus aureus by human monocytes and the biochemical pathways involved. Anti-Fc gamma RI or anti-Fc gamma RII mAb, but not anti-Fc gamma RIII mAb, efficiently stimulated the intracellular killing of bacteria by monocytes. Cross-linking Fc gamma RI or Fc gamma RII, but not Fc gamma RIII, on monocytes with mouse anti-Fc gamma R mAb followed by bridging with F(ab')2 fragments of goat anti-mouse IgG enhanced this process. Since the NADPH oxidase inhibitor diphenyleneiodonium blocked the Fc gamma R-mediated intracellular killing of S. aureus, oxygen-dependent bactericidal mechanisms are most probably involved. Cross-linking Fc gamma RI or Fc gamma RII but not binding of the mAb to the Fc gamma R on monocytes activated phospholipase C, as demonstrated by the increase in the intracellular concentration of inositol-(1,4,5)-triphosphate. The enhanced intracellular killing stimulated by cross-linking Fc gamma R on monocytes was completely blocked by U-73122, an inhibitor of phospholipase C-dependent processes. Protein kinase C activity, but not the rise in the cytosolic free Ca++ concentration or pertussis toxin-sensitive G proteins, is essential for the Fc gamma R-mediated intracellular killing of bacteria by monocytes. Together, these results demonstrate that cross-linking Fc gamma RI or Fc gamma RII is equally effective in stimulating the intracellular killing of bacteria by monocytes and that this stimulation is a phospholipase C-dependent process.

Coagulation parameters of CPD fresh-frozen plasma and CPD cryoprecipitate-poor plasma after storage at 4 degrees C for 28 days

A pilot study was performed on the storage of plasma and cryosupernatant plasma at 4 degrees C for up to 28 days. Eight bags, four of CPD fresh-frozen plasma (FFP) and four of CPD cryosupernatant plasma (CSP, plasma without cryoprecipitate), were sampled during storage for assays of pH; factors V, VIII, IX, and XI; fibrinogen; prothrombin time; activated partial thromboplastin time (APTT); plasma protein electrophoresis; viscosity; and C1q binding. No changes were found in viscosity or the plasma protein electrophoretic pattern, and there was no detectable immune complex formation. The fibrinogen concentration remained constant, and the prothrombin time showed a gradual increase of 2.5 seconds for both groups of plasma. The labile coagulation factor V decreased gradually for FFP and CSP to 58 and 64 percent of its initial value, respectively (51 +/- 8% and 54 +/- 6% of the value of fresh pooled plasma). Factor VIII decreased to 36 percent of its initial value in FFP (48 +/- 14% of fresh pooled plasma). In CSP, factor VIII decreased after 28 days to 7 percent of its initial value (7 +/- 1% of fresh pooled plasma). The APTT increased for FFP from 28 to 35.8 +/- 1.1 seconds and for CSP from 36 to 49.5 +/- 4.9 seconds. The only chemical change observed for both plasmas was a rise in pH, from 7.27 to 7.56, after 28 days. The results of this pilot study indicate that FFP can be stored at 4 degrees C for 28 days with sufficient recovery of coagulation factors to maintain hemostasis.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

The Waldeyer ring equivalent in the rat. A model for analysis of oronasopharyngeal immune responses

By means of serial sectioning of the head and neck a paired, rod shaped, parachoanic lymphoid organ was identified in Lewis rats. Histological, ultrastructural studies and FACS analysis showed this organ to be a lympho-epithelial organ with high endothelial venules (HEV) and a preponderance of B over T and T helper over T suppressor cells. Consequently this organ resembles the pharyngeal tonsil of man, and it is called the Waldeyer ring equivalent (WRE). The lymphatic drainage of this organ occurs predominantly to the deep, and to a lesser extent to the superficial cervical lymph nodes. Migration studies with 51Cr labeled cells show that the WRE lymphoid cells migrate into the lymphoid organs with HEV (peripheral lymph nodes. Peyer patches and WRE). In this respect they resemble peripheral lymph node cells more than cells from the Peyer patches. Thus the WRE lymphoid tissue in the rat is undoubtedly involved in local oronasopharyngeal immune surveillance and may also contribute to mucosal and systemic immune responses.

Spectroscopic studies on IgG aggregate formation

Spectroscopic techniques have been used to examine the effects of IgG of heating, irradiation by ultraviolet light and exposure to glutaraldehyde. Relatively few changes were observed in treated IgG which remained unaggregated but several significant size-dependent changes were observed in aggregated IgG. These results suggest that IgG aggregate formation by cross-linking with glutaraldehyde involves the least perturbation of the basis IgG structure, whereas aggregate formation by heating involves the most, with ultraviolet irradiation occupying an intermediate position.

Immune complexes in sera from patients with rheumatoid vasculitis induce polymorphonuclear cell-mediated injury to endothelial cells

The ability of sera from 11 patients with rheumatoid arthritis (RA) complicated by leukocytoclastic vasculitis (RV) to induce injury to cultured monolayers of human umbilical vein endothelial cells (HEC) was investigated. Injury was assessed in vitro using assays of cell lysis and cell detachment. Sera from patients with RV produced neither direct injury to HEC monolayers nor indirect injury when cocultured with HEC and normal peripheral blood polymorphonuclear cells (PMN). However, immune complexes (Icx) isolated from these sera induced nonlytic PMN-mediated HEC detachment. The inhibitory effect of serum on PMN-mediated HEC detachment induced by Icx could be attributed both to a different response of PMN to Icx present in serum compared to isolated Icx and to the presence of protease inhibitors in serum. The results of this study show that sera from patients with RV do not contain factors that can injure HEC directly and provide further support for the hypothesis that Icx and PMN play important roles in the pathogenesis of immune vascular injury.

An analysis of the fluid phase C1q binding assay. The effect of endogenous C1q on the precipitation and detection of an immune complex model

We examined the effect of endogenous C1q on the sensitivity of the fluid-phase C1q binding assay (C1qBA) in detecting an immune complex (IC) model, heat-aggregated IgG (HAIgG), at concentrations of 10-10,000 micrograms/ml sample. Results in normal human serum (NHS) or plasma (NHP) were compared with those in heat-inactivated NHS (NHS/56) in which most endogenous C1q was depleted by heat denaturation. Higher HAIgG concentrations were required in NHP and NHS to produce the same 125I-C1q precipitation seen in NHS/56. This decreased sensitivity varied from 70% at low HAIgG concentrations to 0% at high concentrations, as predicted for a large pool of endogenous C1q, in equilibrium with 125I-C1q, but in excess of that which could bind to all but the highest concentrations of IC model. In serum depleted of functional C1q on an immunoadsorbant of HAIgG, the precipitation of radiolabeled HAIgG under C1qBA conditions was concentration dependent and generated a saturation curve, showing that only a fraction of IC are usually precipitated in this assay. HAIgG precipitation was enhanced 1.4-fold in NHS/56 (8 micrograms C1q/ml) and three-fold in NHS (67 micrograms C1q/ml) suggesting that IC size is increased by endogenous C1q. In dual label experiments using 131I-HAIgG, the precipitation of 125I-C1q in NHS/56 was directly proportional to IC model precipitation, but markedly discordant in NHP, showing the measurement of IC in heat-inactivated sera superior to that in native serum. A comparison of the C1q:HAIgG ratio in PEG precipitates with that in samples, indicated that equilibrium was established between C1q and IC model. Thus the precipitation of 125I-C1q in the C1qBA represents (1) the fraction of total C1q bound to IC, and (2) the fraction of IC precipitated by PEG.

Lack of evidence for the presence of neutrophil autoantibodies in the serum of patients with Felty's syndrome

Sera of 22 patients with Felty's syndrome and 14 patients with rheumatoid arthritis were tested in assays routinely used for the detection of neutrophil antibodies (i.e. immunofluorescence, agglutination and cytotoxicity tests) as well as in the antibody-dependent lymphocyte-mediated granulocytotoxicity test. One or more of the routinely used assays were positive in a high percentage of the sera (77% and 64%, respectively). The antibody-dependent lymphocyte-mediated granulocytotoxicity test was only positive with sera of three patients with Felty's syndrome. Positive results in the immunofluorescence and agglutination tests could be attributed to the presence of immune complexes in the sera, whereas positive antibody-dependent lymphocyte-mediated granulocytotoxicity tests were probably due to the presence of HLA alloantibodies. It is concluded that serological tests routinely used for the detection of neutrophil autoantibodies should be interpreted with caution in patients with Felty's syndrome. Our results also indicate that the neutropenia in Felty's syndrome is rarely, if ever, due to neutrophil-specific autoantibodies.

Detection of C1q-bearing immune complexes by a monoclonal anti-C1q ELISA system

A monoclonal antibody directed against the collagenous portion of human C1q was used to detect C1q-bearing immune complexes in patients with rheumatic disorders. Sera of patients with rheumatoid arthritis, systemic lupus erythematosus (SLE), osteoarthritis, as well as normal human sera (NHS) used as controls were tested in an ELISA system. C1q-bearing immune complexes were bound to a solid-phase monoclonal anti-C1q antibody, and detected with F(ab')2 antibodies to human IgG. Heat-aggregated human IgG was adjusted to the same concentration as the WHO standard for immune complexes and used for the standard curve in NHS. The mean value in NHS was 19.5 micrograms/ml equivalents of aggregated IgG. Using 2 SD over the mean as the upper limit for normal values, samples greater than 43 micrograms/ml were considered positive. Patients with osteoarthritis were negative; high levels of C1q-bearing immune complexes were detected in patients with rheumatoid arthritis (up to 800 micrograms/ml equivalents of aggregated IgG). With our assay C1q-bearing immune complexes were detected with high frequency (81%) in the sera of patients with rheumatoid arthritis, while a C1q solid-phase binding assay (C1q SPBA) revealed positive results only in 67% of rheumatoid arthritis sera. Compared to NHS, CH50 titers and C1q values of sera from patients with rheumatoid arthritis were frequently high. In contrast, the sera of SLE patients with low CH50 titers and low C1q levels had IgG immune complexes which could be detected only in the C1q-SPBA. C1q-bearing immune complexes were not detectable in the sera of patients with SLE. Since C1q triggers activation of the classical C pathway, this assay with monoclonal anti-C1q antibody appears to be useful for detecting immune complexes in rheumatoid arthritis patients with normal or elevated CH50 and C1q values, especially in the early stage of the disease.

Thermal properties of human IgG

Dynamic light scattering experiments have been performed to study the aggregation kinetics of human immunoglobulin G (IgG). Aggregation and irreversible cluster growth results when IgG solutions (2-15 mg/ml) are heated above 50 degrees C. The measured scattering intensity I and effective hydrodynamic radius (R) can be described consistently by a Smoluchowski aggregation process. The number of clusters ni(t) containing i monomers at time t are computed. The radius of an i cluster is assumed to be Ri = R0 i beta, where beta is the cluster exponent. This kinetic process results in the following characteristic power law behavior: (R)/R0 = (1 + gamma R (T, C, c)t) alpha R and (I)/I0 = (1 + gamma 1 (T, C, c)t) alpha I. Here R0 = 5.51 nm, is the monomer hydrodynamic radius, and I0 the scattered intensity from the monomer solution at temperature T and concn C. A fraction, c approximately 0.48 of the IgG monomers are heat stable up to 63 degrees C and do not participate in the aggregation process. The power-law behavior of mean value of R/R0 and mean value of I/I0 indicates scaling, and indeed a very satisfactory data collapse results from our data. The best non-linear fit of the power-law forms gives alpha R = 0.48 +/- 0.05, alpha I = 1.00 +/- 0.01 and beta = 0.39 +/- 0.04. We also find that the heat aggregation of IgG is an activated process. Fits of the experimental data Gibbs free energy for the activated complex delta G* = 13.8 +/- 0.1 kcal/mole at 56 degrees C. The temp dependence of the growth rates exhibits an Arrhenius behavior with an enthalpy of activation delta H* = 120 +/- 5 kcal/mole.

Immunopathological abnormalities in the normal skin of patients with rheumatoid arthritis in relation to clinical and serological findings: a one year follow up study

Fifty two patients with seropositive rheumatoid arthritis (RA) were studied over a period of one year to investigate possible relationships among changes of circulating immune complexes (CIC), deposits of immunoglobulins and complement around the cutaneous blood vessels, clinical activity of the disease, and the presence of extra-articular manifestations (EAM). The presence or absence of IgM and C3 in and around the cutaneous blood vessels correlated significantly with the presence or absence of extra-articular features in cross sectional and longitudinal studies. Patients with evidence of these cutaneous immune deposits also had a greater prevalence of CIC as determined by the Clq binding assay (ClqBA) or polyethylene glycol (PEG) assay for IC containing IgM (IgM IC). Although the degree of perivascular mononuclear cell infiltration around the blood vessels in the papillary dermis was related to the patients' clinical state at the initial assessment, it did not correlate with the later changes in the activity of the joint disease or the occurrence of EAM. Thus the deposition of immunoglobulin or complement, or both, seems to be independent of cellular infiltration. The meaning of these cellular infiltrates is not yet fully understood. Our study has shown that many patients with RA who appeared to have only joint disease in fact had subclinical systemic disease as reflected by a positive skin biopsy or CIC. Moreover, the disappearance of IgM deposits from the skin correlated with the disappearance of EAM and improvement of joint disease.

Activation of complement by soluble IgG aggregates and their subsequent interaction with macrophages

The mononuclear phagocyte system (MPS) plays an important role in the removal of both particulate and soluble immunogenic material from the circulation. E.IgG adhere to mononuclear phagocytes if the Fc portion of the IgG can interact with the phagocytes' Fc receptors. Simultaneous sensitization with IgG and C3b enhances the effectiveness of binding and ingestion. If soluble material cannot adhere to the surface of macrophages, it will be endocytosed in vitro via fluid-phase pinocytosis at the concentration that is present in the medium. If the material adheres to the cell's surface via its chemical properties or via specific receptors, it will be selectively concentrated at the cell's surface and endocytosed by an adsorptive pinocytosis. Ingestion of IC via Fc gamma R and C3b depends on the ability of the antibodies to interact with Fc gamma R and their capacity to activate the complement system. IC-bound C3b enhances the adsorptive pinocytosis of IC. Soluble AIgG are also pinocytosed more efficiently when C3b is bound to AIgG. The degree of endocytosis varies with the level of C3b sensitization. The highly effective C3b-mediated pinocytosis can be abolished by treating the macrophages with trypsin to inactivate C3bR. This observation illustrates that C3-mediated pinocytosis can replace Fc-mediated pinocytosis in unstimulated macrophages. Soluble IC and AIgG are removed from the circulation mainly by hepatic Kupffer cells. It seems that the size, the Ag/Ab ratio, the capacity of the IC to bind C1, activate C1, and allow deposition of C3b together with the degree of phagocyte activation determine the degree of binding and subsequent degradation of soluble IC.(ABSTRACT TRUNCATED AT 250 WORDS)

Difference in clearance kinetics of particulate immune complexes and soluble aggregates of IgG in vivo

In this study the similarities and differences in kinetics and site of clearance of particulate immune complexes and soluble aggregates of IgG (AIgG) were compared in rats. The rate of clearance of both antibody-coated erythrocytes (EA) and AIgG was dependent on the number of IgG molecules per EA or AIgG. Both probes were rapidly taken up by the liver. Whereas a minor part of the AIgG returned to the circulation as TCA-soluble breakdown products, a substantial part of the injected EA returned to the circulation as intact cells after 4 min. This rebound mechanism was shown to be complement (C)-dependent. Immediately after injection the injected EA bound C3 on their surface, whereafter the number of C3-bearing cells in the circulation rapidly decreased (T1/2 7.2 min). In C-depleted rats relatively more EA were taken up by the spleen than by the liver, in comparison with EA injected into normal rats (liver/spleen ratio in C-depleted rats 0.4 +/- 0.1; in normal rats 2.1 +/- 0.4). When C3 was bound and inactivated by preincubation of EA in vitro, a similar shift from liver to spleen (liver/spleen ratio 0.4 +/- 0.1) was observed. It is suggested that when the hepatic C receptors do not participate, the splenic Fc receptors become relatively more important in the clearance of EA from the circulation.

Spontaneous immunoglobulin synthesis by peripheral mononuclear cells in active rheumatoid arthritis

Spontaneous production of immunoglobulins (Igs) by peripheral blood mononuclear cells (PBMC) in vitro was investigated to assess B cell activity in a group of 24 patients with rheumatoid arthritis (RA) with or without active joint disease and with or without rheumatoid vasculitis (RV) at the time of study. PBMC of patients with active arthritis (Ritchie index above 16) produced significantly more IgG and IgA than those of patients with inactive joint disease or those of 12 healthy controls. Enhanced production of IgG was found mainly among RA patients with concomitant RV, whereas markedly enhanced IgA production could also be found in patients without symptoms of RV. IgM production was only enhanced in two patients who had both active arthritis and RV. High production of IgG and IgA was probably due to increased numbers of Ig-secreting cells among freshly isolated PBMC, since the concentrations of Ig produced in vitro rose steadily, starting on day 0 and persisting throughout the entire culture period. Moreover, IgG and IgA concentrations measured after 7 days of culture showed significant correlations with the numbers of IgG- and IgA-containing plasma cells in PBMC on day 0. Comparison of the spontaneous production of Igs by PBMC with the levels of circulating immune complexes (CIC), showed that CIC levels were also significantly higher in active arthritis and in RV, but that there was no correlation between the CIC levels in individual patients and Ig production by their PBMC in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum immune complexes containing IgA appear to predict erosive arthritis in a longitudinal study in rheumatoid arthritis

Fifty seven patients with rheumatoid arthritis (RA) were studied longitudinally, and the presence of rheumatoid factor (RF) and various types of immune complexes (IC) was correlated with joint activity and the presence of extra-articular features (EAF). In a cross sectional study it was found that the levels of circulating IC and RF correlated significantly with joint disease activity and the presence of EAF. Longitudinally, levels of IC measured by the C1q binding activity and IC containing IgG and IgM correlated significantly with fluctuations in joint disease activity, whereas IC containing IgG and IgA correlated with the occurrence of EAF. RF and IC levels, however, did not predict the clinical course of the disease. IC containing C3 and C4 were found infrequently and were only present in patients with active rheumatoid vasculitis (RV). The continuous presence of these IC appeared to be linked to the recurrence of vasculitis, irrespective of treatment. Significantly more erosions of hands and feet were found after one year follow up in those RA patients who presented early (disease duration less than one year) who initially had a raised serum IgA IC level (r = 0.72; p less than 0.005).

Immune complexes and the pathogenesis of neutropenia in Felty's syndrome

The effect of the injection of serum from patients with rheumatoid arthritis (RA) and Felty's syndrome (FS) into mice on the number of circulating polymorphonuclear cells (PMN) was studied. The number of circulating PMN dropped to 61% (range 34-98%) of the initial counts after the injection of FS serum. This phenomenon was observed less frequently after injection of RA serum. In contrast, injection of serum from healthy controls always resulted in an immediate increase in the number of circulating PMN. No decrease in PMN counts was found after injection of FS sera pretreated with polyethylene glycol to precipitate immune complexes (IC). Gel filtration of FS sera on Sepharose 4B showed that the effect on the PMN counts in mice did not coincide with the 7S peak but occurred only in fractions containing larger material. Serum fractions from FS patients that contained IC were more active in producing neutropenia than the corresponding fractions from patients with RA. Microscopic and immunohistochemical examination of the organs from mice injected with FS serum showed sequestration of PMN and deposition of human IgG, IgA, and IgM in the vascular bed of the lungs. These results indicate that the interaction between PMN and IC of patients with FS leads to sequestration of PMN in mice and suggests that this interaction in humans may have a role in the pathogenesis of FS.

Phagocytosis and intracellular killing of Staphylococcus aureus by polymorphonuclear cells from synovial fluid of patients with rheumatoid arthritis

The phagocytosis and intracellular killing by synovial fluid (SF) polymorphonuclear cells (PMN) of 10 patients with rheumatoid arthritis was studied. PMN phagocytosis was assessed by morphologic and microbiologic methods and intracellular killing was measured independently of continuous phagocytosis of Staphylococcus aureus. Phagocytosis of S aureus by SF PMN or peripheral blood (PB) PMN was as effective in the presence of synovial fluid as in the presence of serum. On average, SF PMN ingested S aureus opsonized with synovial fluid and serum more efficiently than patient or donor PB PMN did. Enhanced ingestion of S aureus was associated with increased expression of C3 receptors on the membrane of SF PMN. In the presence of heat-inactivated synovial fluid, the capacity of SF PMN to ingest S aureus was greater than that of patient or donor PB PMN. Under these conditions, phagocytic activity was correlated with Fc receptor expression. SF PMN was found to be as active in killing S aureus as PB PMN from healthy donors.

Soluble IgG aggregates produced by heating remain stable on freeze-drying

IgG aggregates produced by heating gamma globulin solutions were freeze-dried, kept at 4 degrees C and reconstituted up to 4 months later. By comparison with frozen (-20 degrees C) preparations, only minimal changes in biological reactivity and in physical integrity occurred during this period. These results demonstrate that freeze-dried preparations of heat-aggregated IgG are potentially useful as a reference reagent for the comparative evaluation and standardisation of immune complex assays.

Phagocytosis and intracellular killing by polymorphonuclear cells from patients with rheumatoid arthritis and Felty's syndrome

The present in vitro study concerned the phagocytosis and intracellular killing by polymorphonuclear cells (PMN) of 5 patients with rheumatoid arthritis (RA) and 12 patients with Felty's syndrome (FS). PMN phagocytosis was assessed by microbiologic and morphologic methods, and intracellular killing was measured independently of continuous phagocytosis of viable bacteria (Staphylococcus aureus). PMN from patients with RA or FS ingested S aureus opsonized with immunoglobulins and complement as effectively as did PMN from healthy donors. However, the capacity of patient PMN to ingest S aureus opsonized with sera lacking complement activity, e.g., heat-inactivated donor serum and the sera of 2 patients with FS, was lower than that of healthy donor PMN. This decreased ingestion is associated with diminished expression of Fc receptors on the membrane of PMN from patients who have RA or FS. As with sera lacking complement activity, decreased capacity to ingest S aureus was observed after preloading donor PMN with immune aggregates, which also decreased the expression of Fc receptors. PMN from patients with RA or FS were found to be as active in killing S aureus as cells from healthy donors.

Felty syndrome: autoimmune neutropenia or immune-complex-mediated disease?

Immunofluorescence on polymorphonuclear cells (PMN) of patients with Felty syndrome (FS) revealed increased amounts of IgG, IgA, and IgM bound to the PMN surface compared with PMN of patients with rheumatoid arthritis alone. A positive correlation was found between the score for surface-bound immunoglobulins on FS-PMN and the results of the Clq binding assay in FS sera. After preincubation with sera from 20 patients with FS, immunofluorescence on PMN from healthy controls (HC) showed that these cells had bound IgG, IgA, and IgM. However F(ab')2 fragments of IgG from FS sera did not bind to PMN, although the antigen-binding reactivity of the F(ab')2 fragments was maintained as shown by control experiments. Immunoglobulins eluted from FS-PMN failed to bind to HC-PMN, whereas the corresponding IgG of patients with autoimmune neutropenia was bound. Gel filtration of FS sera on Sepharose 4B showed that the binding of IgG in FS sera to PMN did not coincide with the 7S peak but occurred mainly in fractions containing larger material. No binding of IgA and IgM to HC-PMN was found after incubation with FS sera pretreated with polyethylene glycol (PEG) to precipitate immune complexes. These results indicate that in sera of patients with FS the PMN-binding reactivity of IgG, IgA, and IgM is due to the binding of immune complexes containing these immunoglobulins and not to presence of autoantibodies directed to antigens on the neutrophil surface.

Complement interaction with immune serum globulin and immune globulin intravenous

Three complement assays, C1q binding activity, C3 activation in normal human serum, and enhancement of alternative pathway activity, have been used to evaluate the in vitro anticomplementary activity of untreated and heat-aggregated (63 degrees C, 10 minutes) immune serum globulin and immune globulin intravenous prepared by partial reduction and alkylation. Unheated immune globulin intravenous marginally activated endogenous C3 in normal serum, had a fivefold lower affinity for 125I C1q but was very similar to immune serum globulin in enhancing complement alternative pathway activity. Heat-aggregated immune globulin intravenous was about twofold less effective than heat-aggregated immune serum globulin in the activation of C3 in normal serum and had approximately a threefold lower affinity for 125I C1q. The ability of immune globulin intravenous to retain specific complement receptor activity suggests that it would also retain in vivo efficacy in complement-mediated amplification of host defense reactions but that it is safe for intravenous use due to a lower capacity to initiate nonspecific complement activation.

Direct and quantitative measurement by immunoprecipitation assay of anti-thyrotrophin receptor antibodies in sera of patients with Graves' disease

The presence of anti-TSH receptor antibodies in the sera of 32 patients with untreated Graves' disease, 21 patients with euthyroid autonomous multinodular goitre, nine patients with Hashimoto's disease and 22 normal controls, was investigated by means of a direct and quantitative immunoprecipitation assay (IPA). A comparison was made between the IPA anti-TSH receptor antibody titres, the thyrotrophin-binding inhibitor immunoglobulins (TBII) index determined by radio-receptor assay and the presence of circulating immune complexes (CIC); no correlation was found. Twenty-six (81%) of the 32 untreated patients with Graves' disease were IPA-positive; 16 (50%) had a positive TBII index. None of the patients with euthyroid autonomous multinodular goitre and none of the normal controls were IPA-positive and their TBII index was normal in all cases. Of the nine patients with Hashimoto's disease seven were IPA-positive and three had a positive TBII index. Of ten patients with Graves' disease still in remission none was IPA-positive and their TBII index was normal. Of 18 patients who relapsed after treatment, 13 were IPA-positive and only five had a positive TBII index. In seven patients with Graves' disease studied serially, anti-TSH receptor antibodies remained present in the sera of four, although the TBII indices normalized. For the five patients who relapsed, a rise in the anti-TSH receptor antibody titre at the time of the relapse was observed. It is concluded that not all anti-TSH receptor antibodies cause TSH-binding inhibition in the radio-receptor assay, and further evidence has been obtained that anti-TSH receptor antibodies are the cause of the hyperfunctioning of the thyroid gland in Graves' disease.

Limitations of immune complex measurements in colorectal disease

Three techniques (Clq, Raji and L1210 binding assays) alleged to measure circulating immune complexes (ICs) were applied to the sera of 101 patients with colorectal disease (54 carcinoma; 23 inflammatory; 13 benign tumour and 11 miscellaneous) at the time of diagnostic or definitive surgery, and 58 healthy adult controls. Elevated levels in the pathological sera were observed by all 3 methods in order of sensitivity: Raji greater than Clq greater than L1210. However, none of them differentiated between benign, inflammatory and neoplastic conditions nor, in the case of colorectal carcinoma, was there any correlation with stage of disease. With the exception of Raji v. L1210 (r = 0.43, P less than 0.001), correlations between the various assays were poor and levels of serum carcinoembryonic antigen (CEA) did not correlate with ICs measured by any of the techniques. Indeed, the IC assays were even less discriminatory than CEA, which was elevated mainly in the serum of carcinoma patients and which was positively correlated with serum gamma-glutamyl transpeptidase (gamma GT) (r = 0.42, P less than 0.005). The data suggest that the lack of concordance between the IC assays is a reflection of heterogeneity among ICs, interfering factors present in pathological sera, or both. Thus the IC assays deployed here have neither diagnostic nor prognostic utility in colorectal disease at this time, and immunochemical characterization of the serum reactive material detected by the different assays is required.

The interaction of immune serum globulin and immune globulin intravenous with complement

The in vitro anticomplementary activity of untreated and heat-aggregated (63 degrees C, 10 min) immune serum globulin (ISG) and immune globulin intravenous (IGIV) prepared by partial reduction and alkylation have been evaluated by three assays, C3 activation, binding to C1q and enhancement of alternative pathway lysis of rabbit erythrocytes. Crossed immunoelectrophoresis was used to quantitatively measure the ability of ISG and IGIV to activate endogenous C3 in normal serum. Binding to C1q was determined according to the ability to inhibit binding of 125I-C1q to solid phase IgG. ISG and IGIV enhancement of lysis of rabbit erythrocytes by normal human serum adsorbed with rabbit erythrocytes in the presence of MgEGTA was used to determine activity in the alternative complement pathway. Unheated IGIV at 10 mg/ml only marginally activated endogenous C3 in normal serum, had about a 5-fold lower affinity for 125I-C1q (Ki = 138 to 356 microM vs Ki = 62.5 microM for ISG), but was very similar in ability to ISG on a weight basis in enhancing complement alternative pathway activity (RCH50 = 0.23 to 0.40 mg for IGIV vs 0.17 mg for ISG). Heat-aggregated IGIV at 5 mg/ml in normal human serum was about 2-fold less effective than heat-aggregated ISG in the activation of C3 in normal serum and had approximately 2- to 3-fold lower affinity in the C1q binding assay (Ki = 45 to 83 nM for heat-aggregated IGIV vs Ki = 14.6 nM for heat-aggregated ISG). These data suggest that IGIV prepared by chemical modification retains sufficient specific receptor activity to allow in vivo efficacy in complement-mediated amplification of host defense reactions, but is safe for intravenous use due to a lower capacity to initiate nonspecific complement activation.

Immune reactions in infective endocarditis. II. Relevance of circulating immune complexes, serum inhibition factors, lymphocytotoxic reactions, and antibody-dependent cellular cytotoxicity against cardiac target cells

Circulating immune complexes (IC) were detected in 35 out of 41 patients (85%) with infective endocarditis of known bacterial origin in contrast to only 9 out of 20 patients (45%) with endocarditis but negative blood cultures (p less than 0.05). Peak IC levels of 33.25 +/- 24.33 micrograms/ml in the early period fell significantly to 8.38 +/- 13.37 micrograms/ml after antibiotic treatment (p less than 0.001). High levels of IC coincided with relative hypocomplementemia. Erythrocyturia was observed in 51 of 58 IC-positive patients demonstrating peripheral sequelae of circulating IC. Incidence and concentrations of IC correlated neither with the mere presence of the rheumatoid factor nor with the titers of antimyolemmal antibodies, nor with antibody mediated cytolysis in the presence of complement. Serum inhibition factors (SIF) and E-rosette inhibitory factors (RIF) were not demonstrated, indicating that IC in endocarditis do not suppress phytohemagglutinin-induced lymphocyte proliferation or the E-rosetting of T cells. Significant lymphocytotoxicity against heterologous cardiac target cells without serum (LC) could be demonstrated in 11 out of 23 patients (48%) with endocarditis as compared to its absence in controls (n = 33, p less than 0.01). In assays of antibody-dependent cellular cytotoxicity (ADCC), either enhancement or blocking of lymphocytotoxicity by autologous serum or both was observed. The modulation of lymphocytotoxicity was most likely due to antimyolemmal antibodies, to IC, or to both, although effects of other serum factors cannot be ruled out completely.

Critical aspects of immune complex assays employing polyethylene glycol

Treatment of artificial immune complexes (ICs) with 2.5% polyethylene glycol (PEG)--conditions under which C1q-binding activity is routinely measured in the fluid phase--produced marked changes in molecular size as determined by Sepharose 6B chromatography. The effect of PEG on the C1q-binding capacity of ICs, was therefore investigated using a solid phase (SP) system. PEG enhanced the binding of aggregated human gammaglobulin (AHG) and artificial ICs to SP-C1q and, in reverse experiments, also increased the binding of C1q to SP-AHG. The degree of enhancement varied according to the Ag:Ab ratio employed; the binding of ICs formed in moderate Ab excess was only modestly enhanced but that of complexes formed at slight Ab excess, equivalence and Ag excess was markedly elevated. The profile of PEG-induced enhancement of binding paralleled that of similar ICs in the C1q fluid phase system, suggesting that C1q binding in the latter may be influenced by PEG. However, the C1q-binding activity of in vivo-formed ICs seemed to be relatively unaffected by PEG since enhanced binding was comparable in control and pathological sera. The results indicate that PEG causes cross-linking and aggregation of ICs (and possibly other serum proteins) which may alter their biological activity and hence influence the results of IC assays that employ this agent.

Degradation of soluble immunoglobulin aggregates in vitro by monocytes from normal subjects and from patients with systemic lupus erythematosus

The capacity of human peripheral monocytes to degrade soluble immunoglobulin (IgG) aggregates (AIgG) was studied in vitro. Under serum-free conditions peripheral monocytes from normal donors were able to degrade soluble AIgG in a linear and time-dependent fashion. Addition of fresh human or fresh guinea-pig serum to the incubation mixtures caused a marked increase in degradation of the amount of soluble AIgG available. The stimulatory effect of fresh serum was complement-mediated, because it was abolished by heat treatment of the serum and was not seen when C4- or C3-deficient sera were tested. Functional inactivation of C3 receptors on the phagocytes by trypsin also abolished the complement-mediated stimulation, suggesting cooperation between Fc and C3 receptor in degradation of soluble AIgG. No significant differences were found between monocytes from normal donors and those from patients with systemic lupus erythematosus, as far as degradation is concerned in the presence of complement.

The use of TNP-conjugated polyacrylamide beads in a C1q binding inhibition test for circulating immune complexes

A new assay for the detection of circulating immune complexes is described. It is based on the same principle as the C1q deviation test: the binding of radiolabelled C1q to a solid phase is inhibited by immune complexes. Trinitrophenylated polyacrylamide beads are used as a stable C1q-reactive solid phase in our test. Aggregated IgG in normal serum could be detected by this method to a minimum concentration of about 10 microgram/ml. The test was used to quantitate circulating immune complexes in sera of patients with glomerulonephritis, liver diseases, lymphoma, and myeloid leukemia. The results are compared and correlated with those obtained by the C1q binding assay for the same sera.

The clinical implications and the pathogenetic significance of circulating immune complexes in infective endocarditis

Circulating immune complexes were determined with the 125I-Clq binding assay and the conglutinin binding assay in a prospective, longitudinal study of 40 patients with infective endocarditis, 34 patients with endocardial defects and nonseptic fever and 25 patients with septicemia without endocarditis. Fourteen patients with uncomplicated valvular lesions constituted a control group. Upon admission, 63 percent of the patients with infective endocarditis had a positive 125I-Clq binding assay versus 9, 12 and 7 percent, respectively, of the other three groups (p less than 0.001). The incidence of positive conglutinin binding assays became significantly higher during the course of infective endocarditis (53 percent) than during the course of nonseptic fever (21 percent), but, upon admission, this difference was not significant. The high incidence of Clq-binding immune complexes among patients with infective endocarditis could be attributed mainly to those patients with the characteristic features of subacute endocarditis. The incidence of circulating immune complexes in acute endocarditis was low and did not contribute to making the clinically important distinction from septicemia without endocarditis. A rise in the 125I-Clq binding assay levels during the course of infective endocarditis correlated significantly (p less than 0.01) with failure of antibiotic treatment. With the 125I-Clq binding assay, significantly higher levels were found in patients with signs of renal involvement of cutaneous vasculitis than in patients without these extracardiac manifestations of endocarditis. These results show that the determination of circulating immune complexes has clinical implications for both the diagnosis and the management of infective endocarditis and that circulating immune complexes are probably involved in the development of glomerulonephritis and vasculitis.

Intrinsically stable IgG aggregates

Measurement of the absorbance due to light scattering at 40 nm proved to be a simple and reliable way of assessing the extent of aggregation in heat-treated IgG solutions. Using this technique the rate of aggregation was demonstrated to be markedly temperature dependent with a sharp inflexion in the curve close to 63 degrees C. During heating at 63 degrees C the concentration of unaggregated IgG fell in a manner consistent with a first-order process and the mean size of the IgG aggregates increased with time. IgG aggregates could be selectively removed from heat-treated IgG solutions and concentrated by precipitation with 3.5% polyethylene glycol without altering their size distribution. Furthermore, and in contrast with a previous report, the IgG aggregates examined in this study were remarkably stable in the absence of any other protein such as serum albumin. In consequence, several important practical recommendations concerning the production of heat-aggregated IgG for use in immune complex assays are made.

Binding of fibronectin to Clq; inhibition of binding by aggregated IgG

Fibronectin was shown to bind to C1q using alkaline phosphatase conjugated fibronectin and C1q coated polystyrene tubes. The binding of the alkaline phosphatase conjugated fibronectin to C1q was dose dependent and inhibited by fibronectin and by the sulfated polymers heparin and chondroitin sulfate. The fibronectin interaction was inhibited only slightly by gelatin indicating that the fibronectin-gelatin interaction was different from that with C1q. Heat aggregated IgG blocked the binding of fibronectin to C1q and fibronectin inhibited the binding of aggregated IgG to C1q. These results suggest that fibronectin may be a factor affecting the determination of immune complexes in serum specimens by C1q binding assays.

The specific detection of IgA in immune complexes

An assay to detect IgA in circulating immune complexes (IC) using low avidity goat IgM antibody against human polyclonal IgA is described. The binding of this antibody to IgA coupled to Sepharose 6B is inhibited by IgA-containing IC. The specificity and sensitivity of this anti-IgA inhibition assay (a-IgA-InhA), was evaluated with aggregated purified immunoglobulins, sera of patients with Henoch-Schönlein purpura and normal human sera. Aggregated immunoglobulins of the IgA class, but not monomeric IgA, were reactive. Sucrose density ultracentrifugation showed that large IgA constituents (greater than 19S) were found only in the sera of patients with Henoch-Schönlein purpura. Both these sera and normal human serum contained smaller IgA components (between 7S and 19S), probably small polymers of IgA, which were reactive in this assay and interfered with detection of IgA-containing IC. Redissolved precipitates obtained from normal serum with polyethylene glycol showed reduced reactivity in the test, whereas the inhibitory activity of IgA-containing IC in sera of patients with Henoch-Schönlein purpura was retained in the precipitates. Precipitation of sera with polyethylene glycol allowed detection of smaller quantities of IgA-containing IC in patients with Henoch-Schönlein purpura.

Circulating IgA-immune complexes in Henoch-Schönlein purpura. A longitudinal study of their relationship to disease activity and vascular deposition of IgA

In Henoch-Schönlein purpura immune complexes in inflamed vessel walls characteristically contain immunoglobulin A(IgA). To determine whether IgA is also the predominant immunoglobulin in circulating immune complexes, we compared the results of three immune complex assays with specificities for different classes of immunoglobulins in a longitudinal study of 37 patients (30 children and seven adults) with Henoch-Schönlein purpura. Circulating IgA-containing immune complexes were detected by their reactivity with a low avidity anti-IgA antibody in 27 of the 37 patients. IgA was simultaneously present in cutaneous vessel walls in 95 percent of the patients with circulating IgA-containing immune complexes. High levels of IgA-containing immune complexes were found only during the initial phase of the disease. Immune complexes containing bound complement breakdown products were demonstrated by binding to conglutinin. IgA was found in these immune complexes in 17 patients, IgG in 17 and IgM in nine patients. There was no apparent relation with the class of immunoglobulin in the deposits. Conglutinin-binding immune complexes were present later in the course of the disease and after remission. C1q-binding immune complexes were only found in two patients. These findings suggest that immune complexes-containing IgA may initiate the vasculitis of Henoch-Schönlein purpura, whereas complement-reacted immune complexes containing immunoglobulins of the other classes appear in the circulation in a later phase.

Allergic vasculitis. A histological and immunofluorescent study of lesional and non-lesional skin in relation to circulating immune complexes

This study concerns 57 patients who fulfilled histological criteria for the diagnosis allergic vasculitis. For 37 of these patients, biopsy specimen were available from lesional and adjacent non-lesional skin. Histological signs of vasculitis were found at both sites, but in clinically normal skin the perivascular infiltrate was less dense and neutrophils and eosinophils were sparse or absent. Fibrin was found in only ten patients and occurred less frequently in non-lesional skin. Deposits of immune complexes and/or complement were detected by immunofluorescence in 49 of the 57 patients. Hardly any differences between lesional and non-lesional skin were found with immunofluorescent microscopy. Circulating immune complexes were detected in 45 of the 56 available sera. A relationship was found between the class of immunoglobulin in immune complexes in the vessel wall and in the circulation. Moreover, the class of immunoglobulin seemed to be related to the course, the extracutaneous involvement, and the presence of associated diseases. No explanation was found for the histological differences observed between lesional and non-lesional skin.