Abstract
Purpose: :
Rabbits provide models of several different dacryoadenitides. The rabbits employed at our center are raised outdoors and are exposed to normal changes of temperature and humidity before arrival. In order to determine if environmental variables influence baseline immunoarchitecture and lymphocyte activity, we examined lacrimal glands (LG) from rabbits obtained at three different times.
Methods: :
Virgin adult female rabbits were obtained after 4 wk of mild weather (M); 4 wk of hot, dry weather (HD); and 2 hot, dry wk followed by 2 mild wk (HD→M). Schirmer, rose Bengal, and TBUT tests were performed on Groups M and HD. LG were collected and divided for histology and real-time RT-PCR with species-specific primer-probe sets; mRNA abundances were expressed relative to GAPDH mRNA.
Results: :
TBUT were higher (22.9±0.8 vs. 20.6±0.7), rose Bengal scores were lower (0.56±0.05 vs. 0.96±0.04), but Schirmer scores (with anesthesia) also were lower (3.81±0.19 vs. 4.83±0.15) in Group M vs. Group HD (P<0.05). Group M LG were sparsely populated by lymphocytes; the periductal stroma of Group HD LG frequently contained small, dense lymphocyte aggregates; aggregates were as frequent, but less densely packed, in Group HD→M LG. Compared to Group M, mRNAs for IL-1β, IL-2, IL-4, IL-6, IL-10, prolactin, CD25, and CD28 were 2- to 5-fold (P<0.05) more abundant in Group HD. While most mRNAs correlated strongly with IL-1β mRNA across the three groups, mRNAs for CD25 and CD28 remained elevated while IL-1β declined in Group HD→M.
Conclusions: :
The exceptional stability of the rabbit’s ocular surface fluid film would suggest that physiologic mechanisms mitigate effects of the environment. The present data indicate that rabbit LG indeed react to environmental changes. Numbers and activities of infiltrating lymphocytes increased, TBUT decreased, and rose Bengal staining increased, but basal fluid production also increased after exposure to hot, dry weather. Lymphocyte activity appeared to decrease after mild conditions returned, and persistently elevated CD25 suggested that regulatory lymphocytes might have mediated this change.
Keywords: lacrimal gland • immunomodulation/immunoregulation • cornea: tears/tear film/dry eye