IgD⁺ plasma cells examined in situ for J chain, Cμ deletion, and CCR10 expression. (A) Paired immunofluorescence staining for IgD and J chain in normal lacrimal gland from an IgA-deficient individual. The merge shows that virtually all IgD⁺ plasmablasts and plasma cells are J chain⁺ (yellow cytoplasm) and, thus, of a mucosal phenotype. Epithelial elements (acini) are devoid of IgD, which is not a secretory antibody. IgD^-J chain⁺ cells (purely red in merge) were either IgM⁺ (20%) or IgG⁺ (9.5%) as revealed in adjacent sections (not shown) (× 80). (B) Correlation (Spearman rank test) between the percentage of IgD⁺ plasmablasts and plasma cells relative to other isotypes as determined by immunohistochemistry (logarithmic scale), and the parallel frequency of samples containing B-cell clones with Cμ deletion graded according to the number of PCR products revealed as electrophoretic bands: 1, +; 2-3, ++; and > 3, +++ (see Figure 2B). Open symbols represent IgA-deficient samples. (C) Paired immunofluorescence staining for IgD and CCR10 on sections of 3 tissues as indicated. Merges show many IgD^-CCR10⁺ plasmablasts or plasma cells (presumably mainly IgA⁺) but also several IgD⁺ cells with (arrows) or without (arrowheads) peripheral CCR10 expression. Two CCR10⁺ plasmablasts, one being distinctly double-positive, are seen in tonsillar germinal center (GC) at the border to the mantle zone (MZ), which consists mainly of naive sIgD⁺ B lymphocytes (left, × 60). Extrafollicular area of adenoids (middle, × 100) and glandular area of nasal mucosa (right, × 100) contain many CCR10⁺ large cells.