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Assays for HMGCoA antibodies – practical aspects and clinical utility
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Pathology (2015), 47(S1)
PATHOLOGY 2015 ABSTRACT SUPPLEMENT
time post-mortem or lethal haemorrhage. CPR appears not to affect MCT in femoral samples. A post-mortem MCT >45 mg/L appears to have a specificity for anaphylaxis of approximately 90% and to capture many of the macroscopically problematic cases of anaphylactic vascular collapse. The significance of a moderately raised MCT will depend on clinical plausibility but is enhanced by finding of sIgE to a relevant stimulus such as suspected food or venom, latex, chlorhexidine, suxamethomium, morphine or beta-lactam antibiotic. Complement C4 is the most robust indicator of a potential C1 inhibitor deficiency leading to angioedema.
FLOW CYTOMETRIC ASSAYS TO INVESTIGATE B AND T CELL SUBSETS IN PRIMARY IMMUNODEFICIENCY Cindy S. Ma1,2 1Immunology Department, Garvan Institute of Medical Research, Sydney, and 2St Vincent’s Clinical School, University of UNSW, Sydney, NSW, Australia The focus of our laboratory has been trying to decipher the development, differentiation and function of B and T cells in humans. We do this by studying these lymphocyte populations in primary immunodeficiencies (PIDs) due to monogenic mutations in critical genes. During the course of our study of PIDs, it has become evident that different cohorts of patients display distinct B and/or T cell phenotypes that are often diagnostic even prior to the discovery of the genetic lesion. For example Xlinked lymphoproliferative disease (XLP) is a rare primary immunodeficiency due to mutations in SH2D1A encoding the intracellular adaptor protein SAP. Clinically, XLP patients present with hypogammaglobulinaemia, fulminant infectious mononucleosis, and/or lymphoma. We have previously found SAP is required for the development of NKT cells, which in humans are defined as CD3þVa24þVb11þ cells, and are absent in XLP patients. Furthermore, consistent with hypogammaglobulinaemia, the B cell compartment from XLP patients was found to have a severe reduction in CD27þ memory B cells and Ig class switched cells. More recently we have developed an intracellular staining method for detecting SAP expression. In normal healthy donors SAP can be detected in T cells, but not B cells, as these cells do not express SAP. In XLP patients, SAP is absent in both the B and T cell compartments. Furthermore, XLP carriers can be readily identified, as due to random X-inactivation, they have T cells that are both SAPþ as well as SAP – . Similarly, patients with loss of function mutations in STAT3 and DOCK8 present with a distinct lymphocyte phenotype, which can be readily revealed through flow cytometry-based assays; these will be further discussed.
ANTI-CYTOKINE AUTOANTIBODIES IN INFECTIOUS DISEASES 1,2,3
Julian J. Bosco 1Allergy, Immunology and Respiratory Medicine, Alfred Hospital, Melbourne, 2Immunology Laboratory, Alfred Pathology, and 3Molecular Medicine Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Vic, Australia Cytokines serve as critical effector molecules in immune responses against infection. Inherited mutations that disrupt transcription
factors or cell surface receptors involved in IL-12/IFN-g signalling result in susceptibility to non-tuberculous mycobacterial (NTM) infection and provide vivid confirmation of the importance of these pathways. Similarly, monoclonal anti-cytokine antibodies that target TNF-a have established efficacy in the treatment of rheumatoid arthritis and ankylosing spondylitis, but are associated with increased risk of severe mycobacterial, bacterial and fungal infections. Transient non-pathogenic autoantibodies against cytokines have been reported during acute viral and bacterial infections. Over the past decade, pathogenic high-titre autoantibodies against key cytokines have been increasingly reported in adults with atypical patterns of clinical infection. As an example, autoantibodies against IFN-g have been identified that result in predisposition to more severe and resistant NTM disease. Similarly, anti-GMCSF autoantibodies have been described in cryptococcal meningitis. In the appropriate clinical context, anti-cytokine autoantibodies may be detected by in-house methodologies that include ELISA and multiplex bead arrays. Ideally, these diagnostic tests should be run in parallel with functional studies to confirm disruption of the involved signaling pathways. Ultimately, screening and detection of anti-cytokine autoantibodies may clarify the pathophysiology for certain clinical infections and facilitate targeted therapy.
NECROTISING AUTOIMMUNE MYOPATHY – CLINICAL ASPECTS Merilee Needham WA, Australia Necrotising autoimmune myopathy, (NAM), also sometimes referred to as immune-mediated necrotising myopathy, is an increasingly recognised condition. It can be caused by HMG CoA reductase inhibitors (statins), via the formation of antiHMG CoA reductase antibodies, anti-SRP antibodies, viral infections and tumours. Clinically it is indistinguishable from polymyositis, being characterised by the subacute onset of symmetrical proximal limb weakness, elevated creatine kinase levels, and irritable myopathic findings on electromyography. Of interest, even at presentation it can be associated with significant muscle atrophy, which is a clinical clue to the underlying diagnosis. A muscle biopsy is essential for the diagnosis, and is distinguished from the other inflammatory myopathies by the absence of prominent inflammatory. Infiltrates and often negative MHC-I staining. This is an important condition to recognise and distinguish from other causes of myocyte necrosis, as it is amenable to immunotherapy, with combinations including prednisolone, methotrexate, azathioprine, mycophenolate, IVIG and rituximab.
ASSAYS FOR HMGCOA ANTIBODIES – PRACTICAL ASPECTS AND CLINICAL UTILITY Ben McGettigan1,2, Chris Bundell1 and Myfanwy Spellerberg2 1PathWest QEII, Perth, WA, Australia, and 2Canterbury Health Laboratories, Christchurch, New Zealand Inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCoAR), otherwise known as statins, are the most commonly prescribed medications worldwide for dyslipidiaemia. Rarely,
Copyright © Royal College of pathologists of Australasia. Unauthorized reproduction of this article is prohibited.
ABSTRACTS
statins can be associated with severe necrotising myositis. Because musculoskeletal side effects are common, there has long been interest in development of a biomarker to guide treatment and prognosis when patients develop muscle symptoms whilst on statins. Recently, a strong association between development of a necrotising myositis and antibodies against HMGCoAR has been described in patients on statins.1 However, the presence of these antibodies has also been found in patients not on statins who have
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other inflammatory myositides. Here I will discuss the immunopathogenesis and clinical utility of HMGCoAR antibodies using clinical examples. Both in-house and commercially available assays will be described using recent experience from two clinical laboratories. Reference 1. Mohassel P, Mammen AL. Statin-associated autoimmune myopathy and anti-HMGCR autoantibodies. Muscle Nerve 2013; 48: 477–83.
Copyright © Royal College of pathologists of Australasia. Unauthorized reproduction of this article is prohibited.
S44
PATHOLOGY 2015 ABSTRACT SUPPLEMENT
Pathology (2015), 47(S1)
Copyright © Royal College of pathologists of Australasia. Unauthorized reproduction of this article is prohibited.
Pathology (2015), 47(S1)
PATHOLOGY 2015 ABSTRACT SUPPLEMENT
time post-mortem or lethal haemorrhage. CPR appears not to affect MCT in femoral samples. A post-mortem MCT >45 mg/L appears to have a specificity for anaphylaxis of approximately 90% and to capture many of the macroscopically problematic cases of anaphylactic vascular collapse. The significance of a moderately raised MCT will depend on clinical plausibility but is enhanced by finding of sIgE to a relevant stimulus such as suspected food or venom, latex, chlorhexidine, suxamethomium, morphine or beta-lactam antibiotic. Complement C4 is the most robust indicator of a potential C1 inhibitor deficiency leading to angioedema.
FLOW CYTOMETRIC ASSAYS TO INVESTIGATE B AND T CELL SUBSETS IN PRIMARY IMMUNODEFICIENCY Cindy S. Ma1,2 1Immunology Department, Garvan Institute of Medical Research, Sydney, and 2St Vincent’s Clinical School, University of UNSW, Sydney, NSW, Australia The focus of our laboratory has been trying to decipher the development, differentiation and function of B and T cells in humans. We do this by studying these lymphocyte populations in primary immunodeficiencies (PIDs) due to monogenic mutations in critical genes. During the course of our study of PIDs, it has become evident that different cohorts of patients display distinct B and/or T cell phenotypes that are often diagnostic even prior to the discovery of the genetic lesion. For example Xlinked lymphoproliferative disease (XLP) is a rare primary immunodeficiency due to mutations in SH2D1A encoding the intracellular adaptor protein SAP. Clinically, XLP patients present with hypogammaglobulinaemia, fulminant infectious mononucleosis, and/or lymphoma. We have previously found SAP is required for the development of NKT cells, which in humans are defined as CD3þVa24þVb11þ cells, and are absent in XLP patients. Furthermore, consistent with hypogammaglobulinaemia, the B cell compartment from XLP patients was found to have a severe reduction in CD27þ memory B cells and Ig class switched cells. More recently we have developed an intracellular staining method for detecting SAP expression. In normal healthy donors SAP can be detected in T cells, but not B cells, as these cells do not express SAP. In XLP patients, SAP is absent in both the B and T cell compartments. Furthermore, XLP carriers can be readily identified, as due to random X-inactivation, they have T cells that are both SAPþ as well as SAP – . Similarly, patients with loss of function mutations in STAT3 and DOCK8 present with a distinct lymphocyte phenotype, which can be readily revealed through flow cytometry-based assays; these will be further discussed.
ANTI-CYTOKINE AUTOANTIBODIES IN INFECTIOUS DISEASES 1,2,3
Julian J. Bosco 1Allergy, Immunology and Respiratory Medicine, Alfred Hospital, Melbourne, 2Immunology Laboratory, Alfred Pathology, and 3Molecular Medicine Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Vic, Australia Cytokines serve as critical effector molecules in immune responses against infection. Inherited mutations that disrupt transcription
factors or cell surface receptors involved in IL-12/IFN-g signalling result in susceptibility to non-tuberculous mycobacterial (NTM) infection and provide vivid confirmation of the importance of these pathways. Similarly, monoclonal anti-cytokine antibodies that target TNF-a have established efficacy in the treatment of rheumatoid arthritis and ankylosing spondylitis, but are associated with increased risk of severe mycobacterial, bacterial and fungal infections. Transient non-pathogenic autoantibodies against cytokines have been reported during acute viral and bacterial infections. Over the past decade, pathogenic high-titre autoantibodies against key cytokines have been increasingly reported in adults with atypical patterns of clinical infection. As an example, autoantibodies against IFN-g have been identified that result in predisposition to more severe and resistant NTM disease. Similarly, anti-GMCSF autoantibodies have been described in cryptococcal meningitis. In the appropriate clinical context, anti-cytokine autoantibodies may be detected by in-house methodologies that include ELISA and multiplex bead arrays. Ideally, these diagnostic tests should be run in parallel with functional studies to confirm disruption of the involved signaling pathways. Ultimately, screening and detection of anti-cytokine autoantibodies may clarify the pathophysiology for certain clinical infections and facilitate targeted therapy.
NECROTISING AUTOIMMUNE MYOPATHY – CLINICAL ASPECTS Merilee Needham WA, Australia Necrotising autoimmune myopathy, (NAM), also sometimes referred to as immune-mediated necrotising myopathy, is an increasingly recognised condition. It can be caused by HMG CoA reductase inhibitors (statins), via the formation of antiHMG CoA reductase antibodies, anti-SRP antibodies, viral infections and tumours. Clinically it is indistinguishable from polymyositis, being characterised by the subacute onset of symmetrical proximal limb weakness, elevated creatine kinase levels, and irritable myopathic findings on electromyography. Of interest, even at presentation it can be associated with significant muscle atrophy, which is a clinical clue to the underlying diagnosis. A muscle biopsy is essential for the diagnosis, and is distinguished from the other inflammatory myopathies by the absence of prominent inflammatory. Infiltrates and often negative MHC-I staining. This is an important condition to recognise and distinguish from other causes of myocyte necrosis, as it is amenable to immunotherapy, with combinations including prednisolone, methotrexate, azathioprine, mycophenolate, IVIG and rituximab.
ASSAYS FOR HMGCOA ANTIBODIES – PRACTICAL ASPECTS AND CLINICAL UTILITY Ben McGettigan1,2, Chris Bundell1 and Myfanwy Spellerberg2 1PathWest QEII, Perth, WA, Australia, and 2Canterbury Health Laboratories, Christchurch, New Zealand Inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCoAR), otherwise known as statins, are the most commonly prescribed medications worldwide for dyslipidiaemia. Rarely,
Copyright © Royal College of pathologists of Australasia. Unauthorized reproduction of this article is prohibited.
ABSTRACTS
statins can be associated with severe necrotising myositis. Because musculoskeletal side effects are common, there has long been interest in development of a biomarker to guide treatment and prognosis when patients develop muscle symptoms whilst on statins. Recently, a strong association between development of a necrotising myositis and antibodies against HMGCoAR has been described in patients on statins.1 However, the presence of these antibodies has also been found in patients not on statins who have
S43
other inflammatory myositides. Here I will discuss the immunopathogenesis and clinical utility of HMGCoAR antibodies using clinical examples. Both in-house and commercially available assays will be described using recent experience from two clinical laboratories. Reference 1. Mohassel P, Mammen AL. Statin-associated autoimmune myopathy and anti-HMGCR autoantibodies. Muscle Nerve 2013; 48: 477–83.
Copyright © Royal College of pathologists of Australasia. Unauthorized reproduction of this article is prohibited.
S44
PATHOLOGY 2015 ABSTRACT SUPPLEMENT
Pathology (2015), 47(S1)
Copyright © Royal College of pathologists of Australasia. Unauthorized reproduction of this article is prohibited.