Hormonal influence on the secretory immune system of the eye: endocrine impact on the lacrimal gland accumulation and secretion of IgA and IgG

The objective of the current investigation was to explore the processes underlying the androgen control of tear IgA and to determine whether hormone exposure also modifies tear IgG content. In addition, studies evaluated the impact of diabetes on the androgen regulation of secretory immunity in the eye. Tears and lacrimal glands were collected from age-matched, adult male rats, which had undergone hypophysectomy, selective ablation of the anterior pituitary, streptozotocin-induced diabetes, sham-surgery and/or orchiectomy and had been exposed to vehicle or physiological amounts of testosterone for varying periods of time. Our findings demonstrated that testosterone administration selectively increased the accumulation of IgA, but not IgG, in tears and lacrimal glands of orchiectomized rats. This hormone effect was associated with a 2-fold enhancement of the IgA transfer from lacrimal tissue to tears; IgA movement was against a gradient. In contrast, androgen exposure had no significant influence on the lacrimal gland/tear transfer of IgG, which was down a 90-fold gradient. Testosterone action on the lacrimal gland appeared to involve an increase in IgA production, but not a consistent alteration in the total number of IgA-containing cells. Similarly, androgen exposure had no impact on the population of IgG-containing lymphocytes in lacrimal tissue. Of interest, ablation of the anterior or entire pituitary in orchiectomized rats, which procedure inhibits testosterone-induced stimulation of tear IgA levels, significantly reduced the total number of IgA-containing cells in the lacrimal gland. Induction of diabetes by streptozotocin injection to orchiectomized rats resulted in diminished tear IgA content and decreased numbers of lacrimal IgA-positive lymphocytes, but did not prevent the testosterone-associated rise in IgA antibody content. In summary, our findings demonstrate that androgens increase the lacrimal gland production and secretion of IgA, but not IgG.