Molecular forms of tear IgA and distribution of IgA subclasses in human lacrimal glands

Tears and sera from 14 subjects were analyzed for IgA levels by radioimmunoassay by use of secretory IgA standards for tear samples and monomeric IgA standards for serum samples. [corrected] Tears from subjects without conjunctival inflammation contained 93% polymeric IgA (pIgA) and 7% monomeric IgA; tears from subjects with conjunctival inflammation had less pIgA (79%). Biopsy specimens of 11 lacrimal glands and one accessory lacrimal gland were obtained from 12 additional subjects. Tissues were stained with polyclonal antisera for immunoglobulins, J chain, and secretory component. In addition, tissues were stained for IgA subclasses with monoclonal reagents specific for IgA1 and IgA2. IgA plasma cells predominated over other types of plasma cells, and most were J chain positive. Secretory component, although absent from the interstitium of the gland, was found in most acinar and ductal cells. The average proportion of IgA1 to IgA2 cells was 56% to 44%. We concluded that the lacrimal system of the human resembles other exocrine systems in the production of predominantly pIgA and the nearly equal occurrence of IgA1 and IgA2 plasma cells.