The role of humoral autoimmunity in gastrointestinal neuromuscular diseases
Dysfunction of the gastrointestinal neuromuscular apparatus (including interstitial cells of Cajal) is presumed to underlie a heterogeneous group of disorders collectively termed gastrointestinal neuromuscular diseases (GINMDs). Humoral (antibody)-mediated autoimmunity directed against ligand- or voltage-gated ion channels or associated proteins involved in neuromuscular transmission is associated with several acquired neuromuscular diseases of the periphery and is now implicated in an increasing number of less well-characterised diseases. Anti-channel antibodies have been reported in small numbers of patients with GINMD, particularly in those with GI dysfunction secondary to an underlying disease such as neoplasia or infection. However, little is known of humoral autoimmunity in primary GINMDs. This thesis investigated the association between anti-channel antibodies and GINMD, and the human GI tract as a potential target of anti-channel antibodies. The presence of anti-voltage- and ligand-gated antibodies was investigated in the serum of patients with primary achalasia, enteric dysmotility and intestinal pseudo-obstruction, and in those with GINMD secondary to Chagas’ disease. The functional effect of sera from some of these patients on colonic smooth muscle contractility was also characterised. Finally, the distribution of six voltage-gated potassium channels (VGKCs), which serve essential roles in the peripheral and central nervous systems and are known targets of pathological autoantibodies, were investigated in all layers of the human GI tract. Our findings suggest that currently recognised anti-channel antibodies are not a common pathogenic factor in primary GINMDs. Anti-channel antibodies, in particular anti-VGKC antibodies, were however found in a significant number of individuals with Chagas’ disease. Furthermore, circulating factors in patients with chagasic GI disease altered GI smooth muscle contractility in vitro which may have pathological relevance to GI dysfunction. VGKCs were found throughout the human GI tract, especially in enteric neurons and epithelial cells, which has significance for both normal function and in relation to the GI tract as a target organ for anti-channel autoimmunity.
AuthorsHubball, Andrew William
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