Intestinal permeability in children with Crohn's disease and coeliac disease.

Mannitol and lactulose were used as probe molecules to measure intestinal permeability in children with active small-bowel Crohn''s disease and with untreated coeliac disease. Mannitol and lactulose were administered by mouth in a moderately hypertonic solution (580 mmol (mosmol)/l), and results were expressed as the ratio of the molecules excreted in urine over five hours. Patients with Crohn''s disease had a sixfold increase in permeability (due to increased lactulose permeability) and those with coeliac disease a fivefold increase (due to decreased mannitol permeability). From these results the test offers potential as a noninvasive investigation in children with small-bowel disease.     

New ideas in thyroid autoimmunity

Endocrine epithelial cells do not normally express human leukocyte antigen (HLA) class II molecules, but do so in a variety of autoimmune diseases. This finding suggests the hypothesis that such inappropriate class II-positive expression may enable these cells to present autoantigens and thus contribute to autoimmune pathogenesis. Indeed, class II-positive thyrocytes can present both exogenous antigenic peptides and intrinsic autoantigens to the appropriate T cells. Class II expression by thyrocytes can be induced by interferon-gamma, and is positively and negatively regulated by thyroid-stimulating hormone and epidermal growth factor, respectively. Furthermore, heterogeneity of thyrocyte class II subregion expression appears to be related to the nature of the inducing stimulus. The complexity of regulatory signals is underlined by findings in type I diabetes: islet beta cells aberrantly express class II in this disease, but class II cannot be induced in normal beta cells by interferon-gamma.