Nancy L. O'Sullivan

Nasal-associated lymphoid tissue is an inductive site for rat tear IgA antibody responses.

The role of nasal-associated lymphoid tissue (NALT) as a mucosal inductive site for tear IgA antibody responses was investigated in the rat model. Fluorescent microspheres were shown to access and be taken up by NALT after intranasal of ocular-topical administration, although fewer microspheres were found in the latter case. Tear IgA anti-DNP antibody responses to dinitrophenylated Streptococcus pneumoniae were 6 micrograms/ml at day 7, 10 micrograms/ml at day 10, and were still detectable on day 21 (5 micrograms/ml) following ocular or gastrointestinal immunization. Intranasal immunization induced tear IgA responses which were 1.7-fold higher at day 7 (10 micrograms/ml), peaked by day 10 (14 micrograms/ml) and were still 1.6-fold higher (8 micrograms/ml) at day 21 than responses of ocular or gastrointestinal groups. These findings suggest that intranasal immunization may be more effective than ocular or gastrointestinal administration in eliciting tear IgA antibody responses and, taken together with the microsphere data, indicate that NALT can serve as an inductive site for ocular mucosal IgA responses.

Lymphocyte Lineages at Mucosal Effector Sites: Rat Salivary Glands

Development of T cell lineages and the role of the thymus as a source of immature T cells in parotid (PG) and submandibular salivary glands (SMG) were studied in Fischer 344 rats using the Thy-1/CD45RC/RT6 expression model. In addition, the phenotypes of salivary gland lymphocytes were compared with other conventional and extrathymic populations. PG mononuclear cells consisted of T cells (38%), B cells (29%), and NK cells (4%). SMG had 19% T cells, 7% B cells, 37% NK cells, and an unusual population of CD3−/RT6+ cells. In comparison with lymph node (LN), both PG and SMG were enriched in immature (Thy-1+) and activated (Thy-1−/CD45RC−/RT6−) T cells. Unchanged percentages of Thy-1+ T cells in PG and SMG following short-term adult thymectomy indicated that immature salivary gland T cells had an extrathymic source. In contrast, thymectomy eliminated LN recent thymic emigrants. SMG had T cells with characteristics of extrathymic populations, expressing TCRγδ+ (28%), the CD8αα homodimer (11%), and NKR-P1A (66%). Many SMG T cells expressed integrin αEβ7. PG T cells resembled those isolated from LN in respect to TCR and CD8 isoform usage, but were enriched in αEβ7+ T cells and in NKT cells. Thus, salivary gland mononuclear cells are composed of a variety of subpopulations whose distributions differ between SMG and PG and are distinct from LN. These studies provide a basis for further investigation of regionalization in the mucosal immune network and are relevant to the design of vaccine regimens and intervention during pathological immune processes.

Development of T cell lineages in rat lacrimal glands

Purpose. The purpose of this study was to examine T cell development in rat lacrimal glands, determine whether the thymus is the source of immature T cells in this tissue and compare lacrimal gland T lymphocytes with other T cell subpopulations. Methods. Mononuclear cells were isolated from lacrimal glands of normal or thymectomized female Fischer 344 rats and stained for flow cytometric analysis. Results. The lacrimal gland T lymphocyte population included large percentages of cells with an activated phenotype and also subpopulations of immature, naive and memory T cells. The numbers of immature (Thy-1 +) lacrimal gland T cells were unchanged following short-term adult thymectomy. In comparison, spleen had large percentages of naive T cells, only a small subpopulation of activated T cells, and similar percentages of immature (Thy-1 +) T cells, which were nearly eliminated after thymectomy. Lacrimal gland T cells had small subpopulations of TCR?d + and CD8aa + T cells, a large subpopulation of NKT cells and many integrin aEß7 + T cells. Conclusions. Lacrimal gland T cells are composed of a variety of subpopulations whose composition is distinct from splenocytes. The marked reduction of immature splenic T cell percentages eleven days after adult thymectomy indicates that these cells were mostly derived from thymic precursors. In contrast, the unchanged percentages of immature lacrimal gland T cells following thymectomy indicate that they may have an extrathymic source. These studies provide a foundation for further investigation into the cellular basis of lacrimal gland immunobiology.

Nasal-associated lymphoid tissue is not an absolute requirement for the induction of rat tear IgA antibody responses.

Purpose/Aim of study: The purpose of this work was to determine whether rat nasal-associated lymphoid tissue is required for the induction of tear IgA responses. Materials and Methods: Particulate antigen in the form of DNP-BSA encapsulated in cationic microparticles was applied topically to the eyes (ocular topically) of rats that had the nasolacrimal ducts temporarily plugged with chromic gut suture material. Eye washes and serum were monitored for development of antigen specific IgA and IgG, respectively. To track the particulate uptake, fluorescent latex beads were applied topically to the eyes of plugged and unplugged animals. The nasal-associated lymphoid tissue and the draining lymph nodes were then examined for the presence of the fluorescent beads. Results: It was found that the chromic gut suture was effective in blocking the passage of antigen into the nasopharyngeal cavity for at least 24 hr. Tear antigen-specific IgA levels found in the eyes of plugged animals were not significantly lower from those of unplugged animals. Serum IgG antibody levels were also similar between the two groups. In animals with plugged nasolacrimal ducts, fluorescent beads were found predominately in the superficial cervical lymph nodes, which have been shown to drain the surface of the eye. Conclusions: These results indicate that particulate antigen can be taken up by the conjunctiva and transported to the draining lymph nodes, showing that antigen does not need to access nasal-associated lymphoid tissue to induce tear IgA antibody responses.

Regulation of Lacrimal Gland Immune Responses

The purpose of this review is: (1) to consider the relationship of the lacrimal gland to the mucosal network and general factors regulating lacrimal gland immune responses, (2) to present current data from selected studies on lacrimal gland immunoregulation, and (3) to discuss the future directions of lacrimal gland immunobiology and regulation.

Chapter 86 – Ocular Mucosal Immunity

This chapter reviews the immunologic architecture and regulation of the ocular mucosal immune system and explores the impact of ocular infection and autoimmune disease on this systems structure and function. The mucosal immune system defends the ocular surface against antigenic challenge. The epithelia of the cornea, the conjunctiva, and the lacrimal drainage system, the tear film, the lacrimal glands, and the eyelids act as a functional unit to preserve the quality of the refractive surface and protect ocular structures. The principal tissues involved in the immunologic protection of the ocular surface are the lacrimal gland and the conjunctiva. The lacrimal gland, which serves as the predominant source of tear S-IgA antibodies, is the primary effector tissue in the eyes secretory immune defense. The preocular tear film plays a critical role in the eyes defense against microbial and antigenic exposure, as well as in the maintenance of corneal clarity and visual ability. These functions are extremely dependent upon the stability, tonicity, and composition of the tear film structure. Other tissues, organisms, and factors involved in nonspecific mucosal defense of the eye include the: orbital skeletal structure—which minimizes potential trauma, eyelid architecture—which is relatively impermeable to macromolecules, eyelid blink reflex and ciliary movement—which rapidly clears foreign objects from the ocular surface, and continuous tear flow and reflex tearing—which acts to remove microorganisms and cellular debris through hydrokinetics and eventual drainage into the nasolacrimal duct.

Inductive Sites for Rat Tear IgA Antibody Responses

The mucosal immune system is an important mediator of acquired immunity at the ocular surface.1,2 In mammals, the lacrimal gland serves as the predominant source of tear IgA3,4 and functions as an effector site for mucosal antibody responses.1,2 Evidence for the linkage of lacrimal glands to the mucosal network has come from cell trafficking5,6 as well as antibody expression data.7–9 In a number of species, oral or gastrointestinal antigen stimulation has resulted in tear IgA antibody induction.7–12 In addition, topical application of particulate antigen7–9 or microparticle-encapsulated soluble antigen13 to the conjunctiva (ocular topical, OT) has been documented to be an effective means of eliciting tear IgA antibody responses. Furthermore, evidence indicates that nasal-associated lymphoid tissue (NALT) is a major inductive site in the mucosal immune network,14,15 and NALT appears to serve as an inductive site for tear IgA antibody responses.16