Revision of Ab L chains by secondary rearrangement in mature B cells has the potential to change the specific target of the immune response. In this study, we show for the first time that L chain revision is normal and widespread in the largest Ab producing population in man: intestinal IgA plasma cells (PC). Biases in the productive and non-productive repertoire of λ L chains, identification of the circular products of rearrangement that have the characteristic biases of revision, and identification of RAG genes and protein all reflect revision during normal intestinal IgA PC development. We saw no evidence of IgH revision, probably due to inappropriately orientated recombination signal sequences, and little evidence of κ-chain revision, probably due to locus inactivation by the κ-deleting element. We propose that the λ L chain locus is available and a principal modifier and diversifier of Ab specificity in intestinal IgA PCs.
BackgroundRecent developments in magnetic resonance imaging have enabled demonstration of endolymphatic hydrops, and the clinical application of these imaging studies in Ménière's disease is being explored.ObjectiveTo evaluate our centre's experience to date of hydrops magnetic resonance imaging in patients with episodic vertigo.MethodsMagnetic resonance imaging was performed using a high-resolution three-dimensional fluid-attenuated inversion recovery sequence on a 3 Tesla scanner at 4 hours following double-dose gadolinium administration.ResultsThe study included 31 patients, 28 of whom had a clinical diagnosis of Ménière's disease. In unilateral Ménière's disease, magnetic resonance imaging was able to lateralise endolymphatic hydrops to the clinically symptomatic ear in all cases. Mild hydrops was often seen in clinically asymptomatic ears.ConclusionThere is a good correlation between the clinical symptoms and lateralisation of hydropic changes on magnetic resonance imaging. Further refinements of imaging techniques and grading system will likely improve the diagnostic accuracy and clinical utilisation of hydrops magnetic resonance imaging.
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