IgA-Producing Plasma Cells at the Human Ocular Surface and Reduced Tear IgA2 Abundance in Dry Eye Disease and Primary Sjögren’s Syndrome

To characterize the distribution of IgA-producing plasma cells across the human ocular surface and to assess alterations in tear IgA subclass profiles in Schirmer strip extracts from patients with dry eye disease (DED) and primary Sjögren’s syndrome (pSS). Immunofluorescence staining was performed on paraffin-embedded lacrimal gland, conjunctival, and corneal tissues to identify IgA- and subclass-producing B/plasma cells. Samples were collected from controls (n = 18), patients with DED (n = 75), and patients with pSS (n = 10). Total protein concentrations in Schirmer strip extracts were deter-mined using a bicinchoninic acid assay. Total IgA, IgA1 and IgA2 were quantified by ELISA and normalized to total protein. IgA-producing plasma cells were abundant in the lacrimal gland and conjunctival stroma but absent from the corneal sections. In both tissues, IgA1-producing cells predominated over IgA2-producing cells. Total protein concentrations in Schirmer strip extracts were significantly lower in pSS than in DED. The most consistent change was reduced normalized IgA2 abundance in Schirmer strip extracts, whereas changes in IgA1 were less consistent across the analyzed disease groups. IgA-producing plasma cells are prominent in the lacrimal gland and conjunctiva. DED and pSS are associated with reduced normalized IgA2 abundance and altered IgA sub-class profiles.