Characteristics of human IgA and IgM genes used by plasma cells in the salivary gland resemble those used in duodenum but not those used in the spleen

Immunologically, the parotid salivary gland is an effector site that secret es large quantities of polyspecific Abs into the saliva, mainly of the IgA isotype. It is considered to be part of the common mucosal immune system bu t the inductive site for the Ab-producing cells of the salivary gland has n ot yet been clearly identified. The origin and diversity of cells of B line age can be investigated by analyzing their Ig heavy chain genes (Ig(H)). We have obtained sequences of IgM and IgA V(H)4-34 genes from plasma cells in human salivary gland, duodenal lamina propria, and splenic red pulp. Relat ed sequences were found in different areas sampled within each tissue studi ed, indicating that the plasma cells carrying these genes are widespread wi th limited diversity. Examples of related Ig(H) genes that are isotype swit ched were also seen in the salivary gland. The genes from plasma cells of t he salivary gland were highly mutated, as were duodenal plasma cell sequenc es. The level of mutation was significantly higher than that seen in spleni c plasma cell sequences. Analysis of CDR3 regions Showed that the sequences from salivary gland had significantly smaller CDR3 regions than sequences from spleen, due to differences in number and type of D-H regions used. Seq uences from duodenum also had smaller CDR3 regions. Therefore, plasma cells from human duodenum and salivary gland showed characteristics that differe d from those of human splenic plasma cells.