To determine whether a proliferation-inducing ligand (APRIL) has a role in the survival of plasma cells infiltrating salivary glands from SS patients.
We performed immunological staining for APRIL in minor salivary glands from SS with a pair of antibodies specifically recognizing APRIL-producing cells and secreted APRIL.
Despite high leucocyte infiltration, APRIL-producing cells, identified as neutrophils, were rare in SS salivary glands. Keratinocytes from the adjacent oral epithelium also produced APRIL, but we never detected significant levels of secreted APRIL in SS salivary glands. We obtained similar results with B-cell lymphomas associated with SS. In fact, there was no significant difference in APRIL production and the level of secreted APRIL in these pathological samples compared with normal corresponding tissues.
The combined observation that APRIL production is not up-regulated in lesions from SS patients, and that secreted APRIL is not retained in these lesions, indicates that plasma cells frequently present in SS lesions may not rely on APRIL for survival, as they do in other rheumatic diseases.