No abstract

The mucosa of the conjunctiva is an important site of entry for environmental Ags as well as Ags emanating from the eye itself. However, very little is known about T cell recognition of Ag introduced through this important mucosal site. We have characterized the in vivo process of CD4 T cell recognition of Ag delivered via the conjunctival mucosa. Application of soluble OVA to the conjunctiva of BALB/c mice induced potent T cell tolerance. APC-presenting OVA peptide in vivo was only found in the submandibular lymph node and not in other lymph nodes, spleen, or nasal-associated lymphoid tissue. Similarly, in TCR transgenic DO11.10 adoptive transfer mice, OVA-specific CD4+ T cell clonal expansion was only observed in the submandibular lymph node following conjunctival application of peptide. These experiments thus define a highly specific lymphatic drainage pathway from the conjunctiva. OVA-specific T cell clonal expansion peaked at day 3 following initiation of daily OVA administration and gradually declined during the 10-day treatment period, but remained elevated compared with nontreated adoptive transfer mice. During this period, the T cells expressed activation markers, and proliferated and secreted IL-2 in vitro in response to OVA stimulation. In contrast, these cells were unable to clonally expand in vivo, or proliferate in vitro following a subsequent OVA/CFA immunization. These results suggest that Ag applied to a mucosal site can be efficiently presented in a local draining lymph node, resulting in initial T cell priming and clonal expansion, followed by T cell anergy.

Coral reefs typically occur in oligotrophic waters, where tight recycling of energy and nutrients is essential in order to support their high productivity. Sponges are efficient filter feeders that host diverse and abundant microbial communities that often contain members capable of carrying out complex nutrient transformations. Consequently, sponges often act as significant sources of bioavailable forms of nitrogen and phosphorus while acting as sinks for dissolved organic carbon (DOC). However, little attention has focused on variability of nutrient release by sponges and no studies have reported how abiotic conditions may impact sponge‐driven changes in nutrient concentrations. Here, we show that a common Caribbean sponge, Ircinia felix, is capable of being both a source and a sink for DOC, ammonium, nitrate/nitrite ( NOx−), and phosphate ( PO43−). Additionally, we show that abiotic conditions, particularly ambient nutrient availability, seem to explain a significant amount of the variability (R2 range from 0.40 to 0.65). Interestingly, as ambient nutrient concentrations increased, I. felix transitioned from acting as a source to serving as a sink for all nutrient forms measured. We also found I. felix‐associated bacteria exhibit a significantly higher abundance of predicted nitrogen metabolism, carbon fixation, and photosynthetic genes relative to ambient water and sediment. These results suggest that sponges play an important and dynamic role in biogeochemical cycling on reefs, particularly as human activities alter natural nutrient dynamics in coastal systems.

No abstract