Immune complex assays: diagnostic and clinical application

The Dynamics of Circulating Immune Complexes in Horses with Severe Equine Asthma

Simple Summary

Equine asthma syndrome is a cost-consuming equine respiratory disease of the lower airways in horses. Non-invasive biomarkers from blood or urine are sought. The aim of this study was to assess the circulating immune complexes (CICs) during the exacerbation and remission of an asthma episode—with and without additional treatment and the potential usefulness of CIC levels in the diagnosis, monitoring, and treatment progression. The control group, asthma group, and treated asthma group each contained six horses. The horses were kept in a dusty environment for seven days and then moved to an asthma-friendly environment for over three weeks (the treated group received injections of glucocorticoids). Blood was collected at baseline and on the 1st, 2nd, 3rd, 7th, 14th and 30th days. CICs measured in the time points did not show statistical differences. When CICs were analysed within the groups, there was a significant decrease in CIC in the treated group and a significant increase in CIC in the non-treated group on day 30. CIC did not support the diagnosis procedure of equine asthma syndrome, although it may help in monitoring patients with and without treatment. To the best of the authors’ knowledge, this is the first study to analyse the dynamics of CIC in equine asthma patients during an environmental challenge, remission, and treatment.

Abstract

Non-invasive diagnostic biomarkers of equine asthma syndrome (EAS) from blood or urine are sought. The aim of this study was to assess the absorbance of circulating immune complexes (CICs) during the exacerbation, remission, and treatment of an asthma episode and assess the potential usefulness of CIC levels in the diagnosis and monitoring of the disease. The control group, asthma group, and treated asthma group each contained six horses. Following an initial examination and group classification, the horses were kept in a dusty environment for seven days and then moved to an asthma-friendly environment for three weeks (the treated group received injections of glucocorticoids). Blood was collected at baseline and on the 1st, 2nd, 3rd, 7th, 14th and 30th days. CIC was measured using the modified Haskova method. The time points did not show significant statistical differences. There was a significant decrease in CIC in the treated group, and a significant increase in CIC in the non-treated group on day 30. CIC did not support the EAS diagnosis, although it may help in monitoring patients. To the best of the authors’ knowledge, this is the first study to analyse the dynamics of CIC during environmental challenge, remission, and treatment.

Research on the occurrence of Mycobacterium tuberculosis antigens in the circulating immune complexes, isolated from serum of patients with tuberculosis

Background

Tuberculosis is one of the most dangerous infectious diseases and has among the highest mortality rates of all infectious diseases. There are 9 million cases of active tuberculosis reported annually; however, an estimated one-third of the world’s population is infected with Mycobacterium tuberculosis and remains asymptomatic. Despite the great progress in its diagnosis and treatment, tuberculosis is still a serious health and social problem. The contact between the immune system and Mycobacterium tuberculosis initiates cell-specific (Th1) and humoral-specific (Th2) responses. Many studies about the presence of antituberculotic antibodies in the serum have produced inconsistent results because of a high proportion of false-positive or false-negative results. The purpose of this study was to confirm whether circulating immune complexes (CIC) isolated from the serum of patients with tuberculosis are accompanied by antigenic proteins typical of Mycobacterium tuberculosis.

Material/Methods

We assayed serum samples from 42 patients with tuberculosis. The control group consisted of the sera samples taken from 45 healthy subjects. The immunochemical analysis of dissociated immune complexes using the dot blot method demonstrated positive reaction on the presence of Mycobacterium tuberculosis antigens in all patients with tuberculosis.

Results

All patients with tuberculosis demonstrated a high serum concentration of CIC protein. The mean serum concentration of CIC protein was significantly higher in patients than in controls: 0.081 g/l in the control group and 0.211 g/l in the tuberculosis patients.

Conclusions

The analysis of CIC suggests that it may be a helpful test for patients with tuberculosis because of its quickness, simplicity of the idea, and limited invasiveness.

Do regulatory antibodies offer an alternative mechanism to explain the hygiene hypothesis?

The 'hygiene hypothesis', or lack of microbial and parasite exposure during early life, is postulated as an explanation for the recent increase in autoimmune and allergic diseases in developed countries. The favored mechanism is that microbial and parasite-derived products interact directly with pathogen recognition receptors to subvert proinflammatory signaling via T regulatory cells, thereby inducing anti-inflammatory effects and control of autoimmune disease. Parasites, such as helminths, are considered to have a major role in the induction of immune regulatory mechanisms among children living in developing countries. Invoking Occam's razor, we believe we can select an alternative mechanism to explain the hygiene hypothesis, based on antibody-mediated inhibition of immune responses that may more simply explain the available evidence.

The search for laboratory measures of outcome in rheumatoid arthritis

A large number of laboratory tests have been developed within the past decade to measure factors involved in the immune inflammation of RA. These can be divided into genetic markers, general measures of inflammation, autoantibodies and tissue-specific markers. In general, it is simpler to prove the power of a certain test to measure the disease process than to predict outcome. Apart from RF positivity and CRP/ESR, few, if any, tests have proven to be of importance in independent studies from different centres. Among the promising candidates for future work are detailed analysis of the HLA-D region genes, sulphoxidation status, the autoantibody against RA33 nuclear antigen, soluble IL-2 receptor measuring lymphocyte activity, hyaluronate/hyaluronan or PIIINP from synovial tissue, the combined use of COMP and proteoglycan epitope tests for cartilage matrix, and pyrodinoline cross-linking for collagen from bone and cartilage. The ideal setting for testing such markers are prospective cohort studies starting early in the disease, and since many such studies have been initiated recently, one can expect much new information in coming years. Attention needs to be devoted to the kinetics of marker metabolism, since many are degraded or removed at very fast rates from the circulation, making serum assays less informative.

Immunoglobulin isotype composition of circulating and intra-articular immune complexes in patients with inflammatory joint disease

The immunoglobulin (Ig) heavy chain isotype composition of intra-articular and circulating immune complexes (ICs) were determined by a Raji cell flow cytometric assay in paired serum and synovial fluid samples from 15 patients with rheumatoid arthritis (RA) and 15 patients with other articular diseases (osteoarthritis, ankylosing spondylitis, gout, psoriatic arthritis, Reiter's disease). ICs were most prevalent in synovial fluid samples of patients with RA but were infrequently detected in serum and synovial fluid samples from the non-RA patients. ICs in patients with RA were heterogeneous both in the prevalence of Ig subclasses identified and in the distribution of the respective Ig isotypes within the complexes. Furthermore, differences were observed in the Ig isotype composition of ICs in paired serum and synovial fluid samples indicating that circulating ICs may not always arise simply by spill-over from articular sites. The possible mechanisms for IC formation in RA are discussed with reference to four patients who displayed features of extra-articular disease.

Translocation of the nuclear autoantigen La to cell surface: assembly and disassembly with the extracellular matrix

La (SS-B) protein is known as one major antigenic target for autoantibodies from patients with certain autoimmune diseases such as Sjogren's syndrome or Lupus Erythematosus. La protein belongs to the so called "extractable nuclear antigens". Here we report that La antigen is not restricted to the nucleus as one might deduce from the exclusive nuclear staining pattern of patient anti-La antibodies but after stimulation of serum-starved cells with 10% fetal calf serum (FCS) appears and stays for at least 45 min at the outer surface of CV-1 cells being available for binding of anti-La antibodies. In addition we found that a minor part of La antigen associates with the extracellular fibronectin network. After addition of 10% FCS to serum starved cells this extracellular autoantigen disassembled from the extracellular matrix and was taken up again by the cells. Incubation of serum starved cells with mercuric chloride, a known potent inducer of autoantibodies, also resulted in a detachment of the extracellular matrix associated La protein. From our studies it becomes likely that La protein itself is the antigen during autoimmunization. Moreover, once developed, anti-La antibodies might be able to bind to cell surface expressed La protein resulting in a damage of these cells leading to the inflammational events known to occur during disease.