An improved anti-C3/IgG ELISA for quantification of soluble immune complexes

Autopolyreactivity Confers a Holistic Role in the Immune System

In this review, we summarize and discuss some key findings from the study of naturally occurring autoantibodies. The B-cell compartment of the immune system appears to recognize almost all endogenous and environmental antigens. This ability is accomplished principally through autopolyreactive humoral and cellular immune receptors. This extended autopolyreactivity (1) along immunoglobulin gene recombination contributes to the immune system's ability to recognize a very large number of self and non-self constituents; and (2) generates a vast immune network that creates communication channels between the organism's interior and exterior. Thus, the immune system continuously evolves depending on the internal and external stimuli it encounters. Furthermore, this far-reaching network's existence implies activities resembling those of classical biological factors or activities that modulate the function of other classical biological factors. A few such antibodies have already been found. Another important concept is that natural autoantibodies are highly dependent on the presence or absence of commensal microbes in the organism. These results are in line with past and recent findings showing the fundamental influence of the microbiota on proper immune system development, and necessitate the existence of a host-microbe homeostasis. This homeostasis requires that the participating humoral and cellular receptors are able to recognize self-antigens and commensal microbes without damaging them. Autopolyreactive immune receptors expressing low affinity for both types of antigens fulfil this role. The immune system appears to play a holistic role similar to that of the nervous system.

A simple immune complex dissociation ELISA for leishmaniasis: standardization of the assay in experimental models and preliminary results in canine and human samples

Visceral leishmaniasis, caused by Leishmania (Leishmania) chagasi, is a chronic parasitic disease of humans and dogs. Confirmation of the protozoal agent in bone marrow, lymph node or spleen aspirate is diagnostic, while specific-IgG serology is used mainly for epidemiology despite the general presence of high levels of serum immunoglobulin. Anecdotal reports of false-negative serology in active disease cases are known and are ascribed to the formation of immune complexes. Because dissociation of immune complexes can be accomplished by acid treatment, we devised a simple, routine enzyme immunoassay (ELISA) for the dissociation of immune complexes in serum samples using acid treatment in wells adsorbed with Leishmania antigen (dELISA). Confirmatory acid dot-blot was also developed for antigen detection by anti-Leishmania rabbit antiserum. In experimental L. chagasi hamster models, immune complexes interfered with ELISA mostly in the 30 and 60 days postinfection, according to both dELISA and antigen dot-blot results. In larger samples from endemic areas, dELISA was positive in 10% of seronegative dog samples (7/70) and 3.5% in negative human samples (3/88), showing that dELISA could be used in the serodiagnosis of visceral leishmaniasis. Moreover, dELISA could be used as an alternative approach to screening asymptomatic visceral leishmaniasis patients, instead of invasive confirmatory testing.

Long-term administration of IgG2a anti-NK1.1 monoclonal antibody ameliorates lupus-like disease in NZB/W mice in spite of an early worsening induced by an IgG2a-dependent BAFF/BLyS production

The role of natural killer (NK) T cells in the development of lupus-like disease in mice is still controversial. We treated NZB/W mice with anti-NK1.1 monoclonal antibodies (mAbs) and our results revealed that administration of either an irrelevant immunoglobulin G2a (IgG2a) mAb or an IgG2a anti-NK1.1 mAb increased the production of anti-dsDNA antibodies in young NZB/W mice. However, the continuous administration of an anti-NK1.1 mAb protected aged NZB/W mice from glomerular injury, leading to prolonged survival and stabilization of the proteinuria. Conversely, the administration of the control IgG2a mAb led to an aggravation of the lupus-like disease. Augmented titres of anti-dsDNA in NZB/W mice, upon IgG2a administration, correlated with the production of BAFF/BLyS by dendritic, B and T cells. Treatment with an anti-NK1.1 mAb reduced the levels of interleukin-16, produced by T cells, in spleen cell culture supernatants from aged NZB/W. Adoptive transfer of NK T cells from aged to young NZB/W accelerated the production of anti-dsDNA in recipient NZB/W mice, suggesting that NK T cells from aged NZB/W are endowed with a B-cell helper activity. In vitro studies, using purified NK T cells from aged NZB/W, showed that these cells provided helper B-cell activity for the production of anti-dsDNA. We concluded that NK T cells are involved in the progression of lupus-like disease in mature NZB/W mice and that immunoglobulin of the IgG2a isotype has an enhancing effect on antibody synthesis due to the induction of BAFF/BLyS, and therefore have a deleterious effect in the NZB/W mouse physiology.

Cancer-associated immune-mediated syndromes: Pathogenic values and clinical implementation

The ability of tumors to provoke formation of cancer-associated secondary immunodeficiency (CASID) with predominant suppression of CMI and cancer-associated secondary immunodeficiency with clinical autoimmunity syndrome (CASICAS) with triggering of a set of the autoimmune deviations is appearing to be a key event in the restriction of hosts' anti-tumor immunity. Earlier the existence of the above-mentioned syndromes was demonstrated in BCC and GBM patients. In order to reach a point where immunological phenotypes in GBM and BCC can be clarified clinically and, partly, pathogenically, we have conducted a series of studies of typical and atypical types of immune responsiveness in patients with GBM and BCC. For GBM and BCC three scenarios of the involvement of the immune responsiveness have been established in a series of our studies, i.e., (i) malignancy with no immunopathology, (ii) malignancy as CASID, and (iii) malignancy as CASICAS. All of those scenarios demonstrated significant differences in their immune-mediated manifestations which, in turn, were proven to reveal close associative relationships with a specific clinicopathologic type and clinical manifestations of the tumor. CASID and CASICAS share two common features, i.e., (i) signs of immunodeficiency and (ii) a tandem of the deviations within the adaptive and innate links of the host immune responsiveness. At the same time, CASID and CASICAS are distinct pathogenically and clinically, and in terms of depth of the immune deviations observed, CASID patients manifest a breakage in both links, whereas in CASICAS patients, a breakage in the adaptive link would dominate. To get these differences clarified, we summarized major types of the immune imbalances and sets of clinical and clinicopathologic manifestations to illustrate the above-mentioned features in CASID and CASICAS patients. There are distinct close correlations between clinicopathologic features of the disease course and sets of the immune-mediated imbalances in patients harboring the tumors. The latter implicates a panel of the new immunodiagnostic and immunoprognostic criteria for patients with solid tumors, i.e., BCC, MCC and GB, which is of great value for clinical practice. In particular, the blood levels of some of the immunocompetent cells, state of their functional activity, serum titers of the antigenic markers and autoantibodies, apoptotic parameters, and others may be accepted as additional and clinically informative criteria to be implemented for immunological monitoring and immunotherapy of patients with solid tumors.

The major circulating immunosuppressive activity in American visceral leishmaniasis patients is associated with a high-molecular weight fraction and is not mediated by IgG, IgG immune complexes or lipoproteins

Opportunistic infections, due to disease-related immunosuppression, constitute the major cause of death in American visceral leishmaniasis (AVL). Sera from these patients (AVL sera) non-specifically inhibit the in vitro proliferative response of normal human lymphocytes to lectins or antigens. In the present work, the mediation of this inhibition by IgG, immune complexes and low- or very low-density lipoproteins was studied. AVL serum fractions containing proteins with the molecular weight of IgG, and IgG, purified from AVL sera by anion exchange chromatography, did not suppress the lymphoproliferation. Most of the suppressive activity of AVL sera was associated with a fraction containing molecules with molecular weights above 430 kDa. This would be compatible with it being due to immune complexes and/or lipoproteins, and not to soluble IL-2 receptors as reported previously. However, neither of the two possibilities seem to be the case, as (1) depletion of immune complexes by protein-A followed by protein-G chromatographies did not affect the serum suppressive activity, (2) no correlation between immune complex contents and suppressive activities in individual sera was observed, and (3) plasma lipoproteins (VLDL and LDL), purified from AVL patients and from healthy individuals, had the same degree of immunosuppressive activity.

Detection of immune-complexed 9-O-acetylated sialoglycoconjugates in the sera of patients with pediatric acute lymphoblastic leukemia

Although childhood acute lymphoblastic leukemia (ALL) is highly responsive to chemotherapy, reliable techniques are needed to determine treatment outcome. Over expression of 9-O-acetylated sialoglycoconjugates (9-OAcSGs) on lymphoblasts and concomitant anti-9-OAcSGs was found to have a diagnostic and prognostic potential. However, the presence of circulatory immune-complexed antigens remains unknown. The present study was aimed to evaluate whether immune-complexed 9-OAcSGs can be harnessed for better disease management. Immune-complexed antigens were evaluated in ALL sera (n=262) by a Dot-blot using a 9-OAcSAalpha2-6GalNAc-specific lectin, Achatinin-H. Using three serum samples, the inter- and intra-assay imprecision was evaluated as 11-13% and 7-11%, respectively. The recovery of spiked 9-OAcSGs was 84.2-95.4%. The central 95% reference interval for immune-complexed 9-OAcSGs in normal human sera (NHS, n=144) was 2.9-3.4 mug/ml irrespective of sex and age. At disease presentation, the immune-complexed 9-OAcSGs were fivefold higher than NHS, decreased with remission induction and importantly, reappeared with clinical relapse. Sera from patients with other hematological disorders (n=86) showed negligible levels. The Dot-blot demonstrated the potential application of immune-complexed antigen as a disease-specific marker and its efficacy as a sensitive and specific method that could serve as an economical yet effective index for monitoring disease status.

Circulating immune complexes as indicators of environmental contamination

The aim of this study was to examine the effect of environmental contamination on the concentration of circulating immune complexes (CIC) in bovine blood. We determined that in a conventionally ecologically clear district, the CIC concentration in healthy bovine blood serum was within the limits of 0.18-0.52 mg/mL, (mean = 0.31 mg/mL, V = 30.14%). In a conventionally ecologically contaminated district, the CIC concentration in healthy bovine blood serum was detected within the limits of 0.48-0.99 mg/mL (mean = 0.65 mg/mL, V = 17.97%; P < 0.05). The CIC concentration in serum of bovine leukemia virus (BLV)-infected bovines from different districts was within the limits of 0.29-1.76 mg/mL (mean = 0.81 mg/mL, V = 36.67%; P < 0.05). According to these preliminary results of the investigation, it may be supposed that the increased concentration of CIC is closely related to the environmental contamination. Therefore, studies of CIC concentration in healthy mammals are of great importance for the monitoring of anthropogenic factors and can be exploited as an indicator of environmental contamination.

Analysis of Ig/Ig two-component-determined circulating immune complexes (TCIC) provide new insights into host immunity

There have been many reports on circulating immune complexes (CIC), but information regarding Ig/Ig two-component-determined circulating immune complexes (TCIC) is not available. In the present study, we measured the levels of heterogeneous Ig/Ig two-component-determined circulating immune complexes (Ig/Ig-TCIC) in healthy individuals and patients with hepatitis A, Graves' disease and gastric cancer. The heterogeneous Ig/Ig-TCIC was dissected into IgM/IgG-TCIC, IgG/IgA-TCIC and IgA/IgM-TCIC by use of coating and detecting antibodies. The current study has been carried out in 383 cases of healthy individuals, 97 cases of hepatitis A, 108 cases of Graves' disease and 126 cases of gastric cancer. We found that changes on the levels of IgM/IgG-TCIC and IgG/IgA-TCIC is a common feature in patients studied in this study. A total of 71.4% and 80% of patients with gastric cancer had decreased IgM/IgG-TCIC and IgG/IgA-TCIC, respectively. In addition, elevated frequencies were found in patients with hepatitis A and Graves' diseases for IgM/IgG-TCIC (51.5% and 38.0%, respectively) and IgG/IgA-TCIC (29.9% and 19.4%, respectively). In summary, our results suggest that Ig/Ig-TCIC may be a hallmark for evaluation of host immunity. Decreased frequency in gastric cancer and increased frequencies in hepatitis A and Graves' disease forms a peculiar trait for detection of IgM/IgG-TCIC and IgG/IgA-TCIC. Our findings have, thus, provided new insights into circulating immune complexes.