The Raji cell radioimmune assay for detecting immune complexes in human sera

Dengue and the Lectin Pathway of the Complement System

Dengue is a mosquito-borne viral disease causing significant health and economic burdens globally. The dengue virus (DENV) comprises four serotypes (DENV1-4). Usually, the primary infection is asymptomatic or causes mild dengue fever (DF), while secondary infections with a different serotype increase the risk of severe dengue disease (dengue hemorrhagic fever, DHF). Complement system activation induces inflammation and tissue injury, contributing to disease pathogenesis. However, in asymptomatic or primary infections, protective immunity largely results from the complement system’s lectin pathway (LP), which is activated through foreign glycan recognition. Differences in N-glycans displayed on the DENV envelope membrane influence the lectin pattern recognition receptor (PRR) binding efficiency. The important PRR, mannan binding lectin (MBL), mediates DENV neutralization through (1) a complement activation-independent mechanism via direct MBL glycan recognition, thereby inhibiting DENV attachment to host target cells, or (2) a complement activation-dependent mechanism following the attachment of complement opsonins C3b and C4b to virion surfaces. The serum concentrations of lectin PRRs and their polymorphisms influence these LP activities. Conversely, to escape the LP attack and enhance the infectivity, DENV utilizes the secreted form of nonstructural protein 1 (sNS1) to counteract the MBL effects, thereby increasing viral survival and dissemination.

A proteomics-based method for identifying antigens within immune complexes

A novel approach to recover and identify immune complexes (ICs) was developed using size exclusion chromatography (SEC) and affinity chromatography on immunoglobulin binding columns (HiTrap Protein G). The purification process was monitored by 1D SDS-PAGE, protein staining, Western blotting and, finally, liquid chromatography tandem mass spectrometry (LC MS/MS) was used to identify the recovered antigens. This approach was applied to serum with artificially created immune complexes (ICs) comprising vaccine antigen (influenza) and antibody, which led to recovery and identification of influenza peptides within the recovered ICs. This approach was compared with the established method for IC detection and recovery, polyethylene glycol (PEG) precipitation, followed by LC MS/MS. Both approaches successfully enabled capture, recovery and characterization of immunoglobulins and influenza antigen(s) in complex with the immunoglobulins. However, PEG precipitation has the advantage of simplicity and is more suited for large scale studies.

High titres of IgM-bound circulating immune complexes and erythrocytic oxidative damage are indicators of dengue severity

Global incidence of dengue has drastically increased in the last few years. Despite the global morbidity and mortality associated with dengue infection, mechanisms of immune control and viral pathogenesis are poorly explored. Pancytopenias, along with increased oxidative stress, are salient clinical findings in severe dengue patients. Previously, we demonstrated significant differences of circulating immune complexes (CICs) among severe and non-severe dengue patients. Accordingly, here we sought to determine the contributory role of affinity-purified antibody-bound CICs in dengue severity. To characterize intracellular oxidative stress induced by antibody-bound CICs, 5-(and-6)-chloromethyl-2'-7'-dichlorodihydrofluorescein diacetate (DCFDA) was measured by flow cytometry. At the same time, CICs sensitized healthy red blood cells (RBC) and patients' RBC morphology was determined by scanning electron microscopy and flow cytometry analysis. Erythrophagocytosis and ferritin levels were further determined in severe and non-severe dengue patients. Our results showed that the severe patients had high titres of immunoglobulin (Ig)M-bound CICs (P < 0·0001) in their sera, increased intracellular oxidative stress (P < 0·0001), high ferritin levels (P < 0·0001), altered morphology of RBC and finally enhanced erythrophagocytosis. This study shows for the first time that RBC morphology is altered in severe dengue patients. Taken together, this study suggests that the enhanced IgM-bound CICs could contribute to the increased oxidative stress and act directly on RBC destruction of severe dengue patients, and is an important pathophysiological determinant. Hence, IgM-bound CICs can serve as an important laboratory parameter to monitor dengue infection progression.

Kawasaki Disease: The Role of Immune Complexes Revisited

Kawasaki disease (KD) is an inflammatory disease in children associated with vasculitis affecting predominantly the coronary arteries and is now the most common cause of acquired heart disease in children in developed countries. The etiology of KD is unknown but epidemiological studies implicate an infectious agent or toxin, which causes disease in genetically predisposed individuals. The presence of immune complexes (ICs) in the serum of children with KD was established in numerous studies during the 1970s and 80s. More recent genetic studies have identified variation in Fcγ receptors and genes controlling immunoglobulin production associated with KD. In this review we link the genetic findings and IC studies and suggest a key role for their interaction in pathophysiology of the disease.

Antigen-specific antibody Fc glycosylation enhances humoral immunity via the recruitment of complement

HIV-specific broadly neutralizing antibodies (bNAbs) confer protection after passive immunization, but the immunological mechanisms that drive their development are poorly understood. Structural features of bNAbs indicate that they originate from extensive germinal center (GC) selection, which relies on persistent GC activity. However, why a fraction of infected individuals are able to successfully drive more effective affinity maturation is unclear. Delivery of antigens in the form of antibody-immune complexes (ICs), which bind to complement receptors (CRs) or Fc receptors (FcRs) on follicular dendritic cells, represents an effective mechanism for antigen delivery to the GC. We sought to define whether IC-FcR or CR interactions differ among individuals who develop bNAb responses to HIV. Enhanced Fc effector functions and FcR/CR interactions, via altered Fc glycosylation profiles, were observed among individuals with neutralizing antibody responses to HIV compared with those without neutralizing antibody activity. Moreover, both polyclonal neutralizer ICs and monoclonal IC mimics of neutralizer antibodies induced higher antibody titers, higher-avidity antibodies, and expanded GC B cell reactions after immunization of mice via accelerated antigen deposition within B cell follicles in a complement-dependent manner. Thus, these data point to a direct role for altered Fc profile/complement interactions in shaping the maturation of the humoral immune response, providing insights into how GC activity may be enhanced to drive affinity maturation in next-generation vaccine approaches.

Classification analyses for prostate cancer, benign prostate hyperplasia and healthy subjects by SERS-based immunoassay of multiple tumour markers

Prostate cancer (PCa) is a leading cause of cancer-related death among males globally. To date, prostate-specific antigen (PSA), as a typical tumour marker, has been widely used in the early diagnosis of PCa. However, in practical clinical tests, high serum levels of PSA show a high probability for false-positive results, leading to misdiagnoses. In this study, we developed a new classification system for PCa, benign prostate hyperplasia (BPH) and healthy subjects by using a surface-enhanced Raman scattering (SERS)-based immunoassay of multiple tumour markers along with a support vector machine (SVM) algorithm. Silver nanoparticles (AgNPs) as immune probes and SiC@Ag@Ag-NPs SERS as immune substrates were constructed into a sandwich structure to serve as an ultrasensitive SERS-based immunoassay platform of tumour markers. With this assay, the limits of detection for PSA, prostate-specific membrane antigen (PSMA) and human kallikrein 2 (hK2) were as low as 0.46 fg mL^-1, 1.05 fg mL^-1 and 0.67 fg mL^-1, respectively. Furthermore, the serum levels of PSA, PSMA and hK2 in clinical samples were successfully detected using the SERS-based immunoassay platform, and correct classifications of PCa, BPH and healthy subjects were feasible with help of the linear SVM algorithm. These results demonstrate the potential for improving the diagnostic accuracy of PCa. Overall, the linear SVM classification model with multiple tumour markers exhibited good classifications of PCa, BPH and healthy subjects, with a PCa diagnostic accuracy of 70% that was significantly superior to that of the linear SVM classification model based only on the serum level of PSA (50%). Therefore, combining the SERS-based immunoassay with pattern recognition technology can allow for comprehensive analyses of the serum levels of multiple tumour markers to effectively improve the diagnostic accuracy of cancer with potential applications in point-of-care testing.

C1q Solid-Phase Enzymatic Microassay for Detection of Circulating Immune Complexes: Its Application in Human Breast Cancer

Circulating immune complexes (CIC) were detected and quantitated in human breast cancer to monitor the efficiency of mastectomy. For this aim a microimmunoenzymatic test was set up, applying a solid-phase C1q. Features of this assay can be summarized as follows: ability to estimate as low as 10 ng of aggregated human IgG (ΔIgG), good reproducibility and simplicity of execution, and small serum sample required. A group of women with breast cancer at different stages (TNM classification) was tested for CIC, and 31.75 % were positive. Almost all patients submitted to surgery showed a reduction of this parameter thereafter. A parallel study was carried out in another group of women with benign breast disease, and a significant incidence of CIC was found.

Plugging the Leak in Dengue Shock

Recent structural and functional advances provide fresh insight into the biology of the dengue virus non-structural protein, NS1 and suggest new avenues of research. The work of our lab and others have shown that the secreted, hexameric form of NS1 has a systemic toxic effect, inducing inflammatory cytokines and acting directly on endothelial cells to produce the hallmark of dengue disease, vascular leak. We also demonstrated that NS1 exerts its toxic activity through recognition by the innate immune receptor TLR4, mimicking the bacterial endotoxin LPS. This monograph covers the background underpinning these new findings and discusses new avenues for antiviral and vaccine intervention.

Blood-Borne RNA Correlates with Disease Activity and IFN-Stimulated Gene Expression in Systemic Lupus Erythematosus

The loss of tolerance and the presence of circulating autoantibodies directed against nuclear Ags is the hallmark of systemic lupus erythematosus (SLE). Many of these Ags are complexed with short, noncoding RNAs, such as U1 and Y1. The amount of U1 and Y1 RNA complexed with SLE patient Abs and immune complexes was measured in a cross-section of 228 SLE patients to evaluate the role of these RNA molecules within the known biochemical framework of SLE. The study revealed that SLE patients had significantly elevated levels of circulating U1 and/or Y1 RNA compared with healthy volunteers. In addition, the blood-borne RNA molecules were correlated with SLE disease activity and increased expression of IFN-inducible genes. To our knowledge, this study provides the first systematic examination of the role of circulating RNA in a large group of SLE patients and provides an important link with IFN dysregulation.

Recent advances in dengue pathogenesis and clinical management

This review describes and commentates on recent advances in the understanding of dengue pathogenesis and immunity, plus clinical research on vaccines and therapeutics. We expand specifically on the role of the dermis in dengue virus infection, the contribution of cellular and humoral immune responses to pathogenesis and immunity, NS1 and mechanisms of virus immune evasion. Additionally we review a series of therapeutic intervention trials for dengue, as well as recent clinical research aimed at improving clinical diagnosis, risk prediction and disease classification.

Sesamolin enhances NK cell lysis activity by increasing the expression of NKG2D ligands on Burkitt's lymphoma cells

Sesamolin and sesamin are representative lignans found in sesame seed. The present study was designed to demonstrate the anti-cancer activity of sesamolin achieved by increasing the expression level of NKG2D ligands on Raji cells, which are derived from Burkitt's lymphoma. The anti-cancer activity of sesamolin was also compared with that of sesamin. The cytolysis activity of NK cells against Raji was elevated by the pretreatment of sesamolin on Raji, but not by sesamin. We found that higher NKG2D ligand expression increased the sensitivity of sesamolin-treated Raji to NK cell lysis, resulting from a more active ERK signaling pathway. Our results provide evidence that targeting the ERK signaling pathway may enhance the antitumor activity of lignans and that there is a potential immunotherapeutic value for cancer treatment.

Naringenin enhances NK cell lysis activity by increasing the expression of NKG2D ligands on Burkitt's lymphoma cells

Natural killer (NK) cells are capable of identifying and killing tumor cells as well as virus infected cells without pre-sensitization. NK cells express activating and inhibitory receptors, and can distinguish between normal and tumor cells. The present study was designed to demonstrate the importance of the expression level of NKG2D ligands on the Burkitt's lymphoma cell line, Raji, in enhancing NK cell cytolytic activity. Various flavonoids were used as stimulants to enhance the expression of NKG2D ligands. NK cell lysis activity against Raji was not changed by pre-treatment of Raji with luteolin, kaempferol, taxifolin and hesperetin. However, treatment of Raji with naringenin showed increased sensitivity to NK cell lysis than untreated control cells. The activity of naringenin was due to enhanced NKG2D ligand expression. These results provide evidence that narigenin's antitumor activity may be due to targeting of NKG2D ligand expression and suggests a possible immunotherapeutic role for cancer treatment.

Microparticles provide a novel biomarker to predict severe clinical outcomes of dengue virus infection

Shedding of microparticles (MPs) is a consequence of apoptotic cell death and cellular activation. Low levels of circulating MPs in blood help maintain homeostasis, whereas increased MP generation is linked to many pathological conditions. Herein, we investigated the role of MPs in dengue virus (DENV) infection. Infection of various susceptible cells by DENV led to apoptotic death and MP release. These MPs harbored a viral envelope protein and a nonstructural protein 1 (NS1) on their surfaces. Ex vivo analysis of clinical specimens from patients with infections of different degrees of severity at multiple time points revealed that MPs generated from erythrocytes and platelets are two major MP populations in the circulation of DENV-infected patients. Elevated levels of red blood cell-derived MPs (RMPs) directly correlated with DENV disease severity, whereas a significant decrease in platelet-derived MPs was associated with a bleeding tendency. Removal by mononuclear cells of complement-opsonized NS1-anti-NS1 immune complexes bound to erythrocytes via complement receptor type 1 triggered MP shedding in vitro, a process that could explain the increased levels of RMPs in severe dengue. These findings point to the multiple roles of MPs in dengue pathogenesis. They offer a potential novel biomarker candidate capable of differentiating dengue fever from the more serious dengue hemorrhagic fever.

IMPORTANCE

Dengue is the most important mosquito-transmitted viral disease in the world. No vaccines or specific treatments are available. Rapid diagnosis and immediate treatment are the keys to achieve a positive outcome. Dengue virus (DENV) infection, like some other medical conditions, changes the level and composition of microparticles (MPs), tiny bag-like structures which are normally present at low levels in the blood of healthy individuals. This study investigated how MPs in culture and patients' blood are changed in response to DENV infection. Infection of cells led to programmed cell death and MP release. In patients' blood, the majority of MPs originated from red blood cells and platelets. Decreased platelet-derived MPs were associated with a bleeding tendency, while increased levels of red blood cell-derived MPs (RMPs) correlated with more severe disease. Importantly, the level of RMPs during the early acute phase could serve as a biomarker to identify patients with potentially severe disease who require immediate care.

Role of CD61+ cells in thrombocytopenia of dengue patients

Although hematological disorders with salient features of thrombocytopenia have been well documented in dengue patients, the role of CD61-expressing platelets and the megakaryocytic cell lineage in the pathogenesis of dengue virus (DENV) infection remains largely unexplored. A prospective observational study was performed using blood samples and PBMCs from dengue-confirmed patients, as well as from rhesus monkeys (RM) experimentally infected with DENV. Immunohistochemical staining and FACS techniques were applied to evaluate the frequencies of CD61(+) cells that contained DENV antigen. Highly enriched population of CD61(+) cells was also isolated from acute DENV-infected RM and assayed for DENV RNA by quantitative RT-PCR. Results revealed that DENV antigen was found in small vesicles of varying size, and more frequently in anucleated cells associated with platelets in dengue patients. The DENV antigen-containing cells were CD61(+) and appeared to share characteristics of megakaryocytes. Kinetic profiles of CD61(+) cells from DENV-infected RM revealed a transient increase in CD61(+)CD62P(+) cells early after DENV infection. DENV RNA in a highly enriched population of CD61(+) cells from the infected RM was observed during acute stage. Our results indicate that virus containing CD61(+) cells may be directly linked to the platelet dysfunction and low platelet count characteristics of dengue patients.

TLRs and IFNs: critical pieces of the autoimmunity puzzle

Discoveries revealing the molecular basis of innate immune responses, particularly the identification of Toll-like receptors (TLRs) as the major recognition sensors for microbial and even self-molecules, have provided new insights into the pathogenesis of both systemic and organ-specific autoimmune diseases. These insights will permit the development of novel treatment modalities for these disorders.

Complement and its role in protection and pathogenesis of flavivirus infections

The complement system is a family of serum and cell surface proteins that recognize pathogen-associated molecular patterns, altered-self ligands, and immune complexes. Activation of the complement cascade triggers several antiviral functions including pathogen opsonization and/or lysis, and priming of adaptive immune responses. In this review, we will examine the role of complement activation in protection and/or pathogenesis against infection by Flaviviruses, with an emphasis on experiments with West Nile and Dengue viruses.

Vascular endothelium: the battlefield of dengue viruses

Increased vascular permeability without morphological damage to the capillary endothelium is the cardinal feature of dengue haemorrhagic fever (DHF)/dengue shock syndrome (DSS). Extensive plasma leakage in various tissue spaces and serous cavities of the body, including the pleural, pericardial and peritoneal cavities in patients with DHF, may result in profound shock. Among various mechanisms that have been considered include immune complex disease, T-cell-mediated, antibodies cross-reacting with vascular endothelium, enhancing antibodies, complement and its products, various soluble mediators including cytokines, selection of virulent strains and virus virulence, but the most favoured are enhancing antibodies and memory T cells in a secondary infection resulting in cytokine tsunami. Whatever the mechanism, it ultimately targets vascular endothelium (making it a battlefield) leading to severe dengue disease. Extensive recent work has been done in vitro on endothelial cell monolayer models to understand the pathophysiology of vascular endothelium during dengue virus (DV) infection that may be translated to help understand the pathogenesis of DHF/DSS. The present review provides a broad overview of the effects of DV infection and the associated host responses contributing towards alterations in vascular endothelial cell physiology and damage that may be responsible for the DHF/DSS.

Detection of hepatitis B antigen in circulating immune complexes in acute and chronic hepatitis

By using polyethylene glycol precipitation at low concentration (PEG test) and the radiolabeled C1q binding test, immune complexes were detected sera from acute (23/28) and chronic (28/32) hepatitis patients, hemodialyzed patients with chronic hepatitis B surface (HBs) antigenemia (7/19), and asymptomatic HBs antigen carriers (2/11). After treatment of PEG precipitates with acidic pH, heating, or proteolytic enzyme (protease), electroimmunodiffusion or radioimmunoassay revealed the presence of HBs antigen or antibody in dissociated immune complexes in sera from several acute and chronic hepatitis patients. Electron microscopy showed immune complexes of HB virus in 9 of 12 PEG precipitates obtained from PEG-test-positive sera; these 9 precipitates were from patients with acute or chronic hepatitis and the other three from chronic HBs Ag carriers. Free HB virus particles were observed after protease digestion of PEG precipitates. Neither immune complexes nor virus particles were seen in precipitates from PEG-test-negative but HBs-Ag-positive sera from chronic carriers.

Soluble TNF-like cytokine (TL1A) production by immune complexes stimulated monocytes in rheumatoid arthritis

TNF-like cytokine (TL1A) is a newly identified member of the TNF superfamily of ligands that is important for T cell costimulation and Th1 polarization. However, despite increasing information about its functions, very little is known about expression of TL1A in normal or pathological states. In this study, we report that mononuclear phagocytes appear to be a major source of TL1A in rheumatoid arthritis (RA), as revealed by their strong TL1A expression in either synovial fluids or synovial tissue of rheumatoid factor (RF)-seropositive RA patients, but not RF-/RA patients. Accordingly, in vitro experiments revealed that human monocytes express and release significant amounts of soluble TL1A when stimulated with insoluble immune complexes (IC), polyethylene glycol precipitates from the serum of RF+/RA patients, or with insoluble ICs purified from RA synovial fluids. Monocyte-derived soluble TL1A was biologically active as determined by its capacity to induce apoptosis of the human erythroleukemic cell line TF-1, as well as to cooperate with IL-12 and IL-18 in inducing the production of IFN-gamma by CD4(+) T cells. Because RA is a chronic inflammatory disease with autoimmune etiology, in which ICs, autoantibodies (including RF), and various cytokines contribute to its pathology, our data suggest that TL1A could be involved in its pathogenesis and contribute to the severity of RA disease that is typical of RF+/RA patients.

Slower rates of clearance of viral load and virus-containing immune complexes in patients with dengue hemorrhagic fever

BACKGROUND

Although previous studies have revealed the contribution of an initial high level of dengue virus replication to the severe and potentially life-threatening diseases dengue hemorrhagic fever (DHF) and dengue shock syndrome, the involvement of dengue virus in the immunopathological processes during the transition from fever to defervescence, which is a critical stage in determining the progression to DHF, has not been appreciated. Previously, we reported that dengue virus can be detected in the immune complexes of patients with DHF during this period.

METHODS

We investigated plasma dengue viral load, virus in immune complexes, antibody response, complements, and cytokines for 54 patients with dengue fever (a relatively mild form of disease) and 49 patients with DHF. The patients had confirmed secondary infection with dengue virus type 2 from a large outbreak in southern Taiwan in 2002.

RESULTS

Patients with DHF had a significantly higher viral load and a slower rate of clearance than patients with dengue fever. For viral loads >5.7 log RNA copies/mL on the day of defervescence, the positive and negative predictive values for DHF are 0.88 and 0.95, respectively. A higher level and slower decline of dengue virus-containing immune complexes (and a subsequently higher elevation of C5a and soluble interleukin 2 receptor) were found in patients with DHF, compared with patients with dengue fever.

CONCLUSIONS

These findings indicate that slower rates of clearance of viral load and virus-containing immune complexes are associated with subsequent immune activation and contribute to the progression of DHF at this critical stage. Moreover, viral load on the day of defervescence can predict cases of DHF.

Inhibition of rBet v 1-induced basophil histamine release with specific immunotherapy -induced serum immunoglobulin G: no evidence that FcgammaRIIB signalling is important

BACKGROUND

Human basophils and mast cells express the low-affinity immunoglobulin (Ig)G receptor FcgammaRIIB. It has previously been shown in artificial model systems that cross-linking of the high-affinity IgE receptor FcepsilonRI and FcgammaRIIB leads to inhibition of FcepsilonRI signalling.

OBJECTIVE

The aim of the present study was to investigate whether cross-linking of FcepsilonRI and FcgammaRIIB contributes to IgG-mediated inhibition of histamine release in human basophils in a system using the sera from specific immunotherapy (SIT) patients and the major allergen from birch pollen, Bet v 1. As IgG4 furthermore has been proposed to have special blocking properties, we investigated the significance of IgG subclass specificity for this inhibition.

METHODS

Binding of recombinant Bet v 1-IgG complexes to FcgammaRII and IgG-binding activities in the sera from 25 birch pollen-allergic patients treated with SIT were measured using (125)I-rBet v 1. Inhibition of basophil histamine release was assessed by incubating washed leucocytes with complexes of rBet v 1-IgG with or without blocking of FcgammaRII.

RESULTS

We observed low binding of rBet v 1-IgG complexes to FcgammaRII, which was negatively correlated with the relative IgG4-binding activities. Blocking of FcgammaRII did not reverse the SIT-IgG-induced inhibition of basophil histamine release. However, IgG-binding activities correlated significantly with the ability of the SIT sera to inhibit basophil histamine release.

CONCLUSION

We suggest that at least in birch pollen SIT, the contribution of FcgammaRIIB-mediated inhibitory signalling to SIT-IgG-induced inhibition of human basophil histamine release is of minor importance. The main contributor to the inhibitory effect of SIT-induced IgG seems to be blocking of the allergen-IgE interaction.

Dengue: defining protective versus pathologic immunity

Dengue is an expanding public health problem, and an effective vaccine remains elusive. This review discusses how the significant influence of sequential infection with different dengue virus serotypes on the severity of disease can be viewed in terms of beneficial and detrimental effects of heterologous immunity. A more complete understanding of these effects is likely to be critical for predicting optimal vaccine-induced immune responses.

An antigen capture enzyme-linked immunosorbent assay reveals high levels of the dengue virus protein NS1 in the sera of infected patients

We describe the development of a capture enzyme-linked immunosorbent assay for the detection of the dengue virus nonstructural protein NS1. The assay employs rabbit polyclonal and monoclonal antibodies as the capture and detection antibodies, respectively. Immunoaffinity-purified NS1 derived from dengue 2 virus-infected cells was used as a standard to establish a detection sensitivity of approximately 4 ng/ml for an assay employing monoclonal antibodies recognizing a dengue 2 serotype-specific epitope. A number of serotype cross-reactive monoclonal antibodies were also shown to be suitable probes for the detection of NS1 expressed by the remaining three dengue virus serotypes. Examination of clinical samples demonstrated that the assay was able to detect NS1 with minimal interference from serum components at the test dilutions routinely used, suggesting that it could form the basis of a useful additional diagnostic test for dengue virus infection. Furthermore, quantitation of NS1 levels in patient sera may prove to be a valuable surrogate marker for viremia. Surprisingly high levels of NS1, as much as 15 microg/ml, were found in acute-phase sera taken from some of the patients experiencing serologically confirmed dengue 2 virus secondary infections but was not detected in the convalescent sera of these patients. In contrast, NS1 could not be detected in either acute-phase or convalescent serum samples taken from patients with serologically confirmed primary infection. The presence of high levels of secreted NS1 in the sera of patients experiencing secondary dengue virus infections, and in the context of an anamnestic antibody response, suggests that NS1 may contribute significantly to the formation of the circulating immune complexes that are suspected to play an important role in the pathogenesis of severe dengue disease.

Evaluation of cell-mediated immunity and circulating immune complexes as prognostic indicators in cancer patients

Cell-mediated immunity (CMI) and circulating immune complexes (CIC) were estimated in 55 cancer patients and 25 control volunteers to evaluate their prognostic significance. Cancer patients comprised head and neck cancer (11), breast cancer (13), gastrointestinal cancer (10), genitourinary cancer (11), and lymphomas and sarcomas (10). CMI was tested in vitro by early rosette-forming cells (ARFC) and total rosette-forming cell (TRFC) counts. ARFC count in control group was 758.1 +/- 78.09 cells/cumm. In advancing clinical stages of cancer (I-IV), ARFC counts were decreased (i.e., 601.12 +/- 74.96 [p < 0.01]; 494.8 +/- 71.83 [p < 0.001]; 432.44 +/- 36.05 [p < 0.001], and 438.55 +/- 69.99 [p < 0.001] cells/cumm, respectively). TRFC count in control group was 1029 +/- 88.39 cells/cumm. In cancer stages I through IV, these counts decreased significantly (i.e., 699.63 +/- 66.24; 597.55 +/- 82.9; 505.11 +/- 52.56; and 501.55 +/- 69.99 cells/cumm, respectively [p < 0.001]. Dinitrochlorobenzene cutaneous reactivity in vivo was 100% positive in control group, 62.5% positive in cancer stage I, 5% positive in stage II, and negative in stages III and IV. CIC of intermediate size were estimated by polyethylene glycol precipitation (PEG pptn) technique, which detects CIC in the ratio of 2:1 (Ag2Ab). Mean PEG index in control group was 39.5 +/- 4.65; sequential increase in CIC was observed in advancing clinical stages of cancer (I-IV)(i.e., 49 +/- 7.03 [p < 0.01]; 75.38 +/- 44.01 [p < 0.001]; 93.38 +/- 44.57 [p < 0.001]; and 216.00 +/- 147.05 [p < 0.001], respectively). Latex agglutination inhibition (LAI) titer was done to detect CIC as small as 8s, which constitute the opposite polar end of CIC spectrum. LAI titers in control group were nil. However, LAI titers in cancer stages I through IV were 1 +/- 2.64; 8.6 +/- 5.6 (p < 0.001); 12.00 +/- 8.11 (p < 0.001); and 25.77 +/- 9.06 (p < 0.001), respectively. Decrease in CMI and subsequent increase in CIC indicate unfavorable prognosis in cancer patients, and also precede clinical manifestation of increased tumor mass in vivo.

Immune complex specific for the pancreatic duct antigen in patients with idiopathic chronic pancreatitis and Sjögren syndrome

Circulating immune complexes (ICs) containing the pancreatic antigen against SP3-1 monoclonal antibody were measured in patients with idiopathic chronic pancreatitis (ICP) and Sjögren syndrome (SjS) by Raji cell and solid-phase radioimmuno-assays (RIA). The mean serum levels of ICs measured by solid-phase RIA were significantly higher in patients with ICP (n = 23) and SjS (n = 21) than control (n = 15, p < 0.05, p < 0.02, respectively). ICs were positive in 10 patients with ICP (43%) and 12 SjS patients (57%). Raji cell assay also revealed a significantly higher serum ICs levels in patients with ICP (n = 17) and SjS (n = 12) compared with those of control (n = 7, p < 0.025, p < 0.005, respectively). Seven patients with ICP (41%) and 8 SjS patients (67%) had positive ICs. This was in contrast to the normal level of ICs in patients with alcoholic chronic pancreatitis, primary biliary cirrhosis, and chronic thyroiditis. Our analysis demonstrated a significant and positive relationship between RIA and Raji cell assay (r = 0.70, p < 0.05). Our results suggest that ICs specific for SP3-1 may play a role in the pathophysiology of ICP and SjS.

Circulating immune complexes in patients with psoriasis: do they exist?

Sera from 16 patients suffering from active psoriasis without arthropathy (2 guttate, 10 nummular, and 4 mixed type) were examined for the presence of circulating immune complexes. Five routine laboratory assay systems were used, based on C1q-binding or detection of IgG-coupled C1q and C3-breakdown products. In 14 patients, no elevated levels of circulating immune complexes were detected. One patient, who additionally suffered from late-phase HIV-1 infection, showed C1q-binding activities as well as levels of IgG-coupled C1q and C3-breakdown products in four of the assay systems, which indicated the presence of immune complexes in his serum. In another patient, with nummular psoriasis, slightly elevated levels of circulating immune complexes were measured by two of the assay systems. These results question the hypothesis of an essential pathogenic role of circulating immune complexes in psoriasis.

Glomerular lesions induced in the rabbit by physicochemically altered homologous IgG

Immunization of rabbits with physicochemically altered homologous or even autologous IgG induces formation of antibodies combining with IgG of rabbit and of foreign species. Cardiac but not renal lesions were reported in such animals. This study examined the nephritogenic potential of the immune response to cationized or heat-aggregated homologous IgG of b9 or b4 allotype in rabbits of the b4 allotype. Rabbits injected with either b9 or b4 cationized IgG produced antibodies reactive with rabbit and human IgG and with histones; they also developed abnormal glomerular deposits of IgG b4 and C3 corresponding to alterations of the glomerular basement membranes (GBM). Rabbits injected with either b9 or b4 aggregated IgG developed antibodies reactive with rabbit and human IgG and abnormal glomerular deposits of IgG b4 and C3 in the GBM and in the mesangium with subendothelial and mesangial electron-dense deposits. Some rabbits in both groups had proliferative and exudative glomerulonephritis and proteinuria. The results showed that immunization of rabbits with physicochemically altered homologous IgG induces an immune response to rabbit and human IgG and to histones as well as glomerular deposits of autologous IgG and C3 and other glomerular lesions.

Analysis of circulating immune complexes isolated from plasma, cerebrospinal fluid and urine

The protein nature of soluble immune complexes (IC) from fresh plasma, cerebrospinal fluid (CSF), and urine was studied by combining several analytical and biochemical techniques. In plasma and CSF, free immunoglobulins G were separated from larger IC by gel filtration with a fast protein liquid chromatographic system. In urine, IC were separated by precipitation with polyethylene glycol. IC were further purified by protein-A and protein-G affinity chromatography and analyzed by two-dimensional gel electrophoresis. Apart from plasma samples from healthy donors, IC from cases with macrocreatine kinase type 1 and multiple sclerosis were analyzed. For CSF two cases of multiple sclerosis and for urine one case with urinary tract infection are shown. The method can be used for the examination of IC of unknown protein composition in body fluids.

Chromatographic and electrophoretic studies of circulating immune complexes in plasma

The protein nature of soluble immune complexes from fresh plasma was studied by combining several analytical biochemical techniques. Free immunoglobulins (Ig) G were separated from larger immune complexes by gel permeation chromatography. In a second step, immune complexes, free IgA and IgM were isolated by protein-A and protein-G affinity chromatography and analysed by two-dimensional gel electrophoresis. Sixteen plasma samples from healthy donors were analysed and evaluated visually. Their protein profiles on the gels turned out to be similar, showing only slight quantitative differences. In one case, additional proteins were detected. To prove the ability of the method, immune complexes were analysed from four plasma samples that showed macro creatine kinase type 1, a complex formation between creatine kinase BB and IgG. This methodology can be used for the examination of immune complexes of unknown protein composition in serum or plasma.

An investigation on rheumatoid factor of different immunoglobulin classes in hepatitis B virus carriers

Rheumatoid factor (RF) is known to be present very frequently in HB virus carriers. When RF was assayed in 140 asymptomatic carriers by agglutination method, 20.0% were found to be positive, whereas 2.7% in the controls (p less than 0.01). ELISA for detection of RF isotypes showed RF in carriers to be almost IgMRF only. IgMRF showed a tendency to react more readily to human IgG rather than to rabbit IgG. The incidence of IgMRF positivity was higher among anti-HBe antibody-positive carriers than among anti-HBe antibody negative ones, but the difference between the two populations was not significant. However, the incidence of IgMRF positivity in the group showing hepatic dysfunctions was found to be significantly higher than in the group with normal hepatic functions.

A new enzymatic assay for evaluating the clearance of immune complexes from the circulation of mice

A new photometric in vivo enzymatic immune complex clearance (EIC) assay was developed in a homologous system using glucose oxidase-anti-glucose oxidase complexes (GAG) as a model of immune complexes. Chromatographically purified GAG was injected into mouse tail veins and at intervals thereafter the enzyme activities of GAG remaining in the circulation were estimated. The GAG were cleared in a size dependent manner and were stable, being eluted as the same discrete peaks on HPLC size-exclusion chromatography both before and after injection into mice. The complement consuming activity of the GAG was weak, and depletion of complement components with cobra-venom factor did not alter clearance of the GAG from the circulation, whereas pretreatment of aggregated mouse gamma globulin suppressed the clearance rate. These results suggested that most of the GAG were not cleared via complement receptors but via FcR. Normal clearance rates were significantly changed by administration of immunomodulators such as carrageenan or LPS. Intravenous administration of GAG at a dose 50 times higher than normal caused no deaths suggesting that the complexes were of low toxicity. The enzymatic method presented should be of value for measuring the function of the mononuclear phagocytic system with respect to immune complex clearance. It provides a rapid and sensitive alternative assay which avoids using radioisotopes.

Association of autoimmunity with IgG2 and IgG4 subclass deficiency in a growth hormone-deficient child

An association between humoral immune deficiency and childhood autoimmune disease has been previously established. We describe a 7-year-old male with severe autoimmune disease, recurrent infections, a marked deficiency of IgG2 and IgG4, and an inability to respond to polysaccharide antigens. This child was also found to have isolated growth hormone (GH) deficiency. Laboratory results included a positive anti-smooth muscle antibody, a positive Raji-cell assay for immune complexes, and normal levels of IgG, IgM, and IgA. IgG subclasses revealed an IgG1 of 1225 (normal for age, 280-1120 mg/dl), IgG2 of less than 10 (30-630 mg/dl), IgG3 of 36 (40-250 mg/dl), and IgG4 of less than 4 (11-620 mg/dl). No increase in antibody titer was noted to either Pneumovax or unconjugated Haemophilus influenzae vaccine. Numbers of circulating B cells (CD19) were markedly diminished (less than 0.5%). Liver biopsies have shown chronic active hepatitis. Somatomedin C was 0.28 U/ml (normal for age, 0.5-2.06 U/ml). Challenge with either L-dopa or clonidine produced a peak GH response of 2.3 ng/ml (normals = greater than 7 ng/ml). Children with autoimmune disorders should be evaluated for IgG subclass deficiencies and ability to make antibody in response to antigen challenge regardless of the serum immunoglobulin levels. Growth failure in immune-deficient children should not be assumed to be due to chronic illness or recurrent infections. Other etiologies for growth failure should be sought.

Membrane attack complex of complement in Henoch-Schönlein purpura skin and nephritis

The present study using direct immunofluorescence with monoclonal antibodies to C5b-9 complex-related antigens was undertaken to determine whether complement activation in Henoch-Schönlein purpura (HSP) causes assembly of the membrane attack complex of complement (MAC) in skin and nephritis lesions. The deposition of C5, C6, C7, C8, C9, and C5b-9 neoantigens was noted in the vascular walls of papillary dermis and/or subpapillary dermal plexus of the vessels in 11 out of 15 patients with HSP. Their presence in vessel walls indicates complement activation which leads to terminal complement activation. There were small deposits of S protein at the same sites in three of the 11 skin specimens. Thus, the majority of C5b-9 demonstrated in HSP skin was the cytolytically active C5b-9 complex, MAC. Granular deposits of C5b-9 related antigens without S protein were also found in the capillary walls and mesangium of the glomeruli of two out of four specimens from patients with HSP nephritis; in the other two S protein was colocalized with the deposition of C5b-9. The results of the present study indicate that complement activation leading to generation of MAC may possibly be involved in the pathogenesis of vascular injury in a significantly large number of skin lesions and of HSP nephritis.

An analysis of immunocomplexes for the detection of the early stages of colon cancer

A radioimmunoassay was developed for the detection of the early stages of colon cancer by analysis of immune complexes (IC) with a specific polyclonal antibody. Human colon cancer cells were grown in a capillary culture system to provide unaltered antigens for the development of a specific antibody. The antibody was labeled with iodine 125 (125I) and used to analyze the antigen component of IC removed from whole serum. The assay was positive in 50% and 88% of known Dukes' A and Dukes' B colon cancer patients, respectively. It was also positive for only 25% of Dukes' C and 14% of Dukes' D patients, possibly because of the decreased quantity of specific IC found in the late stages of colon cancer. A blind study of patients referred for colonoscopy compared pathology diagnosis with the test results. The assay was positive for one patient with a polypoid adenocarcinoma (Dukes' B) and one with a villous adenoma and negative for 38 patients with benign polyps and 43 with no polyps. The assay was negative for all patients with stomach cancer and inflammatory bowel diseases and positive for about 10% of the patients with pancreas or breast cancer. The results of this preliminary investigation suggest that this radioimmunoassay may be useful for the detection of the early stages of colon cancer.

C3-containing serum immune complexes in patients with systemic lupus erythematosus: correlation to disease activity and comparison with other rheumatic diseases

Although testing for circulating immune complexes (CIC) is regarded as a useful, complementary, laboratory parameter in the differential diagnosis and management of immune complex-induced vasculitis syndromes, there is still an uncertainty with regard to assay systems used for the demonstrated of soluble immune complexes. This is partly due to difficulties in the reproducibility, handling and principle limitations of available test systems for the assessment of soluble immune complexes in body fluids. In the present communication a modification of the anti-C3 test for the determination of CIC was developed using nitrocellulose as a solid phase matrix. IgG-, IgA- and IgM-containing CIC were determined and quantified using standard immune complex preparations. When 39 sera of SLE patients, 12 sera of patients with vasculitis syndromes, 10 sera of rheumatoid arthritis patients and 11 sera of patients with ankylosing spondylitis were tested, predominantly IgG-containing CIC could be demonstrated. Only in SLE patients was a significant amount of other immunoglobulin isotypes detected in CIC. In these patients a significant difference of IgG-containing CIC levels was found with regard to patients with high and low disease activity (P less than 0.0001). A significant correlation was also established between IgG-containing CIC and anti-dsDNA antibodies (P less than 0.001). In a longitudinal study the isotypes in the isolated CIC were found to be constant.

Circulating immune complexes and kidney lesions following 131I administration in mice with thyroglobulin antibodies

Immune complexes containing thyroglobulin have been described in kidneys of some patients with thyroid disease. We investigated the circulating immune complexes (with the Raji cell radioassay) and the kidney histopathology (by immunofluorescence and electron microscopy) in mice that received radioiodine to release thyroglobulin in the circulation, 2 or 4 weeks after immunization with mouse thyroglobulin in Freund's complete adjuvant. Circulating immune complexes and thyroglobulin, antibodies were found in all mice. Granular deposition of IgG, IgM, C3, and thyroglobulin, mainly in the mesangium but also in the capillary walls of the glomeruli, were observed in most of the mice. These experiments suggest that circulating immune complexes composed of thyroglobulin are responsible for the glomerular lesions. Hyperthyroid patients should be tested for thyroglobulin antibodies before treatment with radioiodine to avoid formation of thyroglobulin-containing circulating immune complexes.