Environmental factors determine DAP12 deficiency to either enhance or suppress immunopathogenic processes.

DNAX-activation protein 12 (DAP12), a transmembrane adapter, plays a major role in transducing activation signals in natural killer cells and various myeloid cells. Quantitative RT-PCR detected in normal mouse eyes considerable levels of DAP12 and multiple DAP12-coupled receptors, in particular TREM-1, Clec5a and SIRPb1. The role of DAP12 and its receptors in experimental autoimmune diseases has been controversial. Here, we analysed the effect of DAP12 deficiency on the capacity of mice to mount immunopathogenic cellular responses to the uveitogenic ocular antigen and interphotoreceptor retinoid-binding protein (IRBP), and to develop experimental autoimmune uveitis (EAU). Surprisingly, sequential analysis of EAU in mice deficient in DAP12 in two different animal facilities at first revealed enhanced disease as compared with wild-type mice, but when these mice were re-derived into a second, cleaner, animal facility, the response of control mice was essentially unchanged, whereas the DAP12 null mice were markedly hyporesponsive relative to controls in the new facility. Accordingly, when stimulated in vitro with IRBP, lymphocytes from the DAP12-deficient mice housed in the two facilities proliferated and produced opposite profiles of pro-inflammatory and anti-inflammatory cytokines, compared with their controls. These findings therefore demonstrate that the effects of DAP12 deficiency on development of autoimmune disease are dramatically affected by environmental factors.

Constitutive pro-apoptotic molecules are differentially expressed in the fetal and adult mouse eye.

PURPOSE: To compare gene expression of pro-apoptotic molecules in the fetal and adult mouse eye. MATERIALS AND METHODS: Eyes were collected from groups of BALB/c mice, at embryonic ages E16 and E18 (fetal) or 6-8 weeks of age (adult). RNA extracted from pooled eyes was analyzed by real-time PCR for transcript levels of pro-apoptotic molecules involved in the intrinsic or extrinsic pathway of apoptosis. RESULTS: Transcripts of intrinsic pathway molecules, Bad, Bak, and Bax, were relatively more highly expressed in the fetal mouse eyes, whereas extrinsic pathway molecules, Fas, FasL, and TRAIL had greater expression in the adult eyes. CONCLUSIONS: Different mechanisms of apoptosis are prominent at the fetal and mature stages of the mouse eye.

Complement deposits on ocular tissues adjacent to sites of inflammation.

PURPOSE: The complement system plays important roles in a variety of chronic ocular diseases such as age-related macular degeneration. Here we examined the deposition of complement components in mouse eyes damaged by various mechanisms. METHODS: Mouse eyes were damaged by light or by three models of inflammation, i.e., local transgenic expression of cytokines, interleukin-1 or -7, or by induction of experimental autoimmune uveitis. Eye tissues obtained from each model were immunostained with antibodies against complement components C1q, C3, and C4. RESULTS: No complement deposition was seen in light damaged eyes, while in inflamed eyes we found complement deposition at sites of tissue damage and cellular infiltration. In addition to affected tissues, intense immunoreactivity against complement was unexpectedly observed in corneal tissues and lens capsule, despite lack of inflammation in these tissues. CONCLUSION: Our observations suggest that ocular tissues adjacent to inflammatory sites undergo changes that facilitate complement deposition.