Stereotypic rheumatoid factors that are frequently expressed in mucosa-associated lymphoid tissue-type lymphomas are rare in the labial salivary glands of patients with Sjögren's syndrome

Among autoimmune diseases, Sjögren's syndrome (SS) is most strongly associated with the development of malignant B cell lymphoma, in particular mucosa-associated lymphoid tissue (MALT)-type lymphoma. Previously, we have shown that in ∼40% of cases of salivary gland MALT lymphoma, high-affinity stereotypic rheumatoid factor (RF) B cell receptors, specific for IgG-Fc, are expressed. This study was undertaken to investigate whether in the inflamed salivary glands of patients with SS, a similar RF-biased Ig repertoire is present. Extensive analyses of the B cell Ig VH region repertoire were performed on microdissected tissue samples from the labial salivary glands of 4 patients with SS. All SS labial salivary glands harbored expanded B cell clones, of which 1 or 2 were highly expanded and detected in >50% of the microdissected samples. However, among the identified 464 distinct Ig clonotypes, only 3 stereotypic RF-expressing clones were detected. In 2 patients with SS, an RF-expressing clone was detected at low frequency in 1 of the microdissected samples, whereas 1 patient with SS harbored a highly expanded RF-expressing clone that was detected in all microdissected samples and also detected in the peripheral blood. Two years after analysis of this sample, the latter patient developed a diffuse large B cell lymphoma originating from the same RF clone. Inflamed labial salivary glands in patients with SS generally harbor 1 or 2 highly expanded B cell clones. The repertoire strongly biased toward stereotypic RFs in salivary gland MALT lymphomas is not a reflection of a similar repertoire in the inflamed salivary glands of patients with SS; rather, in the latter, the repertoire is based on a strong selection advantage of incidental stereotypic RF-expressing B cells