The distribution of immunoglobulin-containing cells in human autoimmune thyroiditis

The peroxidase-antiperoxidase (PAP) staining method was used to identify immunoglobulin-containing cells in the lymphoid infiltrates of thyroids removed from patients with Hashimoto's autoimmune thyroiditis. A composite picture of the distribution of such cells in the thyroid infiltrate was obtained by carefully superimposing cell-distribution maps from serial histological sections, each stained for a different immunoglobulin class. Ig-containing cells were present to varying extents in all areas of the gland, but were most dense in areas of epithelial 'invasion'. IgG was the commonest immunoglobulin, but there were more cells containing IgD and IgE than IgA or IgM. Both lambda and K light chains were identified in cells occupying the follicle centres. Lymphoid follicle structure was strikingly similar to that described previously for gut-associated lymphoid tissue (GALT), and the theory is advanced that autoimmune thyroiditis represents a form of ectopic GALT in which B-cells, which normally home on markers in the gut, are attracted instead to antigenically active sites in the thyroid.