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Summary Chronic diarrhoea presents a diagnostic challenge for both human physicians and equine veterinarians. There is currently no consensus in the equine veterinary literature on the definition of chronic diarrhoea. The differential list is extensive and identifying diarrhoea by pathophysiologic mechanism can help remove less likely diagnoses. Achieving a definitive antemortem diagnosis is also challenging. Results from non‐invasive diagnostics may only lead to the conclusion that inflammation is present. Cellular infiltrate, if present, may not be representative of the underlying disease. Invasive diagnostics resulting in acquisition of full‐thickness biopsies may result in a diagnosis when other methods have failed. However, there is currently minimal data correlating these findings with those from full post‐mortem examination. This article discusses the various diagnostic options and reviews the available literature on their value in evaluating currently available patients with chronic diarrhoea. [ABSTRACT FROM AUTHOR]

Objective The serum squamous cell carcinoma antigen (SCCA) level is a well-known tumor marker for squamous cell carcinoma. In this study, we examined the impact of immunoglobulin (Ig)-bound macromolecular SCCA on serum SCCA levels measured by 2 different methods. Methods Seventy-five serum samples with an SCCA level >5.0 ng/mL as determined by a chemiluminescent immunoassay (CLIA) were also analyzed using a chemiluminescent enzyme immunoassay (CLEIA). The levels of IgG- and IgA-type anti-SCCA antibodies, which form immunoglobulins and macromolecules, respectively, were determined using an enzyme-linked immunosorbent assay. An absorption test was performed to confirm the presence of anti-SCCA antibodies. Results The correlation coefficient between the values measured by CLEIA and CLIA was 0.768. The ratio of SCCA levels measured by CLEIA to those measured by CLIA in 14 samples with IgG-type anti-SCCA antibodies was significantly lower than that in samples without these antibodies (P <.031). Absorption tests showed that SCCA levels measured by CLIA might be falsely high in samples with IgG-type anti-SCCA antibodies, probably due to reactions with SCCA1. Conclusion The level of SCCA as measured by CLIA and CLEIA methods correlate well, but the presence of SCCA antibodies can affect the results of the CLIA method. [ABSTRACT FROM AUTHOR]

Monoclonal immunoglobulin-G (IgG) antibodies are now emerging as therapeutic tools to tackle various disorders, including those affecting the brain. However, little is known about how these IgG molecules behave in the brain. To better understand the potential behavior of IgG molecules in the brain, here we established a specific protocol to immunolocalize rat IgG injected into mouse striatum with an anti-rat IgG antibody. Using double immunolabeling, IgG-like immunoreactivity (IR) was mainly found in neurons but scarcely observed in glia 1 h after intrastriatal injection of IgG, whereas some surrounding glia contained IgG-like IR 24 h after injection. However, preabsorption with a large excess of rat IgG to confirm the authenticity of this labeling failed to eliminate this neuronal IgG-like IR but rather exhibited nuclear staining in glial cells. Because this unexpected nuclear staining escalated with increasing amount of absorbing IgG, we postulated that this nuclear staining is due to formation of immune complex IgG–anti-IgG, which can be removed by centrifugal filtration. As expected, this nuclear staining in glial cells was eliminated after centrifugal filtration of the IgG/anti-IgG mixture, and authentic IgG-like IR was chiefly detected in the cytoplasm of neurons around the injection channel. This study is the first demonstration of neuronal redistribution of injected IgG in the mouse brain. Neuronal internalization of exogenous IgG may be advantageous especially when the therapeutic targets of monoclonal IgG are intraneuronal such as neurofibrillary tangles or Lewy bodies. [ABSTRACT FROM AUTHOR]