Unique characteristics of lacrimal glands as a part of mucosal immune network: High frequency of IgA-committed B-1 cells and NK1.1(+) alpha beta T cells

Purpose. Immunologic ch;characterization of IgA-committed B-l and B-2 cells , and unique subsets of T cells isolated from the murine lacrimal gland (LG ), the primary exocrine tissue for the ocular surface. which is considered to be a part of the mucosal immune system. Methods. Single cells were obtained from LGs of C57BL/6 mice by the enzyme dissociation method using collagenase type IV. Samples underwent flow cytom etric analysis to characterize the unique subsets of T and B cells. To test rile effectiveness of ocular vaccination, mice were immunized ocularly or nasally with cholera toxin (CT; 10 mu g/mouse) suspended in phosphate-buffe red saline. Antigen-specific immune responses were determined by isotype an d CT-specific enzyme-linked immunosorbent assay (ELISA) and enzyme-linked i mmunospot (ELISPOT) assay. Results, When mononuclear cells (MC) isolated from LG samples were examined by flow cytometry, approximately 28% of cells were characterized as B220() B cells. Because surface IgA(+) (slgA(+)) B cells develop from B-l and B- 2 lineages, it was important tc, examine which subset of B cells gives rise to LG sIgA(+) B cells. Examination of the MC isolated from LG samples show ed th;ar approximately 4% of cells were sIgA(+) B cells. Furthermore, nearl y all these sIgA(+) B cells (97.5%) belonged to the B-1 lineage, especially the B-la cell line (B220(low), CD5(+)). Of the. isolated CD3(+) T cells, 7 5% were alpha beta and 25% were gamma delta T-cell receptor positive. The p roportion of NK1.1(+) alpha beta T cells was higher (3%) in LG samples than in submandibular,gland samples (0.5%) Ocular immunization with CT-induced antigen-specific mucosal (e.g., found in tear-Rash and saliva samples) and systemic (e.g., serum) immune responses. The magnitude of antigen-specific antibody responses was comparable to those induced by nasal immunization. Conclusions. These results show that LG contains unique subsets of B (e.g., sIgA(+) B-1 cells) :and T (e.g., NK1.1(+) alpha beta T cells) cells. Furth ermore, as a part of the mucosal immune barrier, the LG is an important imm unologic tissue for thr ocular surface.