Harry Irving, Hung Jiew Lee, John Parratt Renal Tubule Antibodies in Multiple Sclerosis and other Neurological diseases Harry Irving, Hung Jiew Lee, John Parratt Discipline of Neurology, The University of Sydney, NSW, Australia, 2006. , Multiple sclerosis (MS) is a debilitating neurological disease characterised by inflammatory lesions scattered throughout the central nervous system (CNS). While the exact cause of MS is unknown, it is generally proposed that the disease is secondary to an autoimmune response against the CNS that is precipitated by complex interactions between environmental and genetic factors. Specifically, autoreactive antibodies have been suggested to play a significant role and various myelin and oligodendrocytic proteins have been listed as possible targets. Currently no CNS autoantibodies have been found to be specific to multiple sclerosis. However, patients with neuromyelitis optica (a demyelinating disease with similarities to MS), have been shown to have disease specific antibodies that react with the water channel aquaporin-4 (AQP-4). AQP-4 autoreactive antibodies bind to stomach, brain and kidney tissue where the molecule is expressed and there is evidence that these antibodies are pathogenic. The current study investigated whether other renal binding autoantibodies occur in MS and other neurological diseases. AIM Determine the frequency of anti-renal proximal tubule antibodies in MS patients. Determine the specific location within proximal tubules where ARTA bind. RESULTS Table 1. Frequency of ARTA in the serum of test groups. METHODS Serum from 126 case patients and 186 controls Indirect immunofluorescence (IIF) was performed on frozen sections of rat renal tissue that had been lightly perfused. - ARTA positivity based on binding intensity score of >++ on a qualitative scale. Indirect immunofluorescence was performed on HK-2 cells (an immortalised human proximal tubule cell line). Doublestaining for Ezrin a marker of microvilli within the brush border and human test serum to determine more specifically the location of the antigenic target of ARTA. RESULTS Figure 2. HK-2 Ezrin v ARTA. Arrowheads indicate ezrin positive microvilli (red). ARTA are present in a granular pattern within the submembrane (green). Nuclei are stained with hoescht (blue). Figure 3. Hk-2 cells v ARTA. Serum binds in a granular submembranous pattern. (A) Binding pattern is not universal with many cells not exhibiting binding at all. (B-D) Examples of ARTA positive HK-2 cells displaying binding within granules under the surface membrane. 2 A A Figure 1. ARTA binding within the proximal tubules of rat renal tissue. Level of ARTA serum was measured in a number of test groups. Above is a representative image of an ARTA positive serum sample with high titre (i.e. >+++). ARTA is present within the apical brush border of proximal tubule cells. 1 50μm A B B C C D Figure Serum from MS patients binds to the renal proximal tubules within the kidneys (Figure 1) ARTA are significantly higher in patients with MS and AE than other groups (p=0.015, Chi-Square with Bonferonni correction) (Table 1) . However, there is no significance in the difference between MS and AE (p>0.05) (Table 1). ARTA positive serum binds beneath the surface of the cell membrane in some cells and not within the microvilli (Figure 2-3). CONCLUSION Current evidence suggests that ARTA are a non-pathogenic, non-specific consequence of neuro-immunological responses. The level of ARTA in healthy control subjects was greater than previously reported. As this study aimed at only identifying frequencies of ARTA within MS and various groups the specificity and identification of the antigenic target was not examined. Further research is required to establish whether ARTA represent a specific autoantibody or if ARTA are the combination of various autoreactive antibodies that bind to separate targets within the renal proximal tubule. References . Goldenberg, M. M. (2012). "Multiple sclerosis review." P T 37(3): 175-184. Nair, A., T. J. Frederick, et al. (2008). "Astrocytes in multiple sclerosis: A product of their environment." Cellular and Molecular Life Sciences 65(17): 2702-2720. AE: Autoimmune encephalitis; ADEM: Acute disseminated encephalomyelitis; AQP-4: Aquaporin-4; CIS: Clinical isolated syndrome; HC: Healthy controls; MS: Multiple Sclerosis; NMO: Neuromyelitis optica, OIND: Other inflammatory neurological disease; OND: Other neurological disease; P: Psychiatric.