Molecular analysis of the influences of positive selection, tolerance induction, and antigen presentation on the T cell receptor repertoire.

Immunization of both B10.A and B10.S(9R) mice with pigeon cytochrome c (pcc) elicits T cells capable of proliferating to pcc presented on I-E major histocompatibility complex (MHC) molecules. The T cell receptor (TCR) repertoire used by pcc-specific T cells from these two strains is markedly different, even for T cells recognizing very similar antigen/MHC complexes. Our current studies have been directed toward explaining this differential expression between MHC congenic strains of TCR gene elements capable of recognizing similar ligands. Analysis of the TCR repertoire of pcc-specific T cells from F1[B10.A x B10.S (9R)]----parent radiation chimeras has demonstrated that much of this difference is a result of the positive selection of T cells for MHC restriction specificity. Further analysis of T cell lines from F1 mice and from radiation chimeras stimulated in vitro with pcc on both B10.A and B10.S(9R) antigen-presenting cells has provided clear-cut examples of the influence of positive selection, tolerance induction and of both in vivo and in vitro antigen presentation on the shaping of the TCR repertoire for a protein antigen. This is the first molecular analysis of how positive selection, tolerance induction, and antigen presentation can combine to mold the TCR repertoire.

Carprofen inhibition of flare in the dog measured by laser flare photometry.

The purpose of this study was to determine whether oral carprofen (Rimadyl(R)) treatment in dogs could prevent or decrease the breakdown of the blood-aqueous barrier. The topical pilocarpine irritative model was used to induce breakdown and cause flare. Pilocarpine was instilled in both eyes of seven dogs at time zero and again 5 h later. At 7 h, laser flare photometry was used to measure the flare concentration in each eye using the Kowa FC-1000 laser flare cell meter. All treatments were then discontinued. Two days later, carprofen was administered to the same dogs for a total of three doses. After the last dose of carprofen, pilocarpine treatments and flare measurements were repeated. Carprofen pretreatment resulted in a 68% inhibition of flare, which was highly significant (P < 0.01). The pilocarpine group had a mean of 16.1 photon counts per millisecond (PC ms-1) +/- 2.2 SE, and the carprofen group had a mean of 7.0 PC/ms +/- 1.2 SE. These results compare favorably with previous studies measuring increased protein or fluorescein concentrations in the aqueous humor after blood-aqueous barrier breakdown in the dog. These results suggest that carprofen may be effectively used as a systemically administered ocular anti-inflammatory drug. Carprofen has the added benefit of fewer reported side effects.

Subconjunctivally implanted micro-osmotic pumps for continuous ocular treatment in horses.

OBJECTIVE: To evaluate the feasibility of using a subconjunctivally implanted micro-osmotic pump for continuous delivery of medication to the eyes of horses- during a 7-day period. ANIMALS: 4 healthy adult horses. PROCEDURE: With horses restrained in a standing position, micro-osmotic pumps were implanted subconjunctivally in each eye for 7 days. The treatment eye received an atropine-loaded micro-osmotic pump (100 microl of 1.5% atropine), and the contralateral eye received a sterile saline-loaded pump (100 microl of 0.9% NaCl) as a control treatment. Pupil size was measured at 12-hour intervals until values returned to baseline. RESULTS: The micro-osmotic pumps were tolerated and did not migrate or become dislodged. During the 7-day treatment period, pupils were significantly larger in the eyes implanted with atropine-loaded pumps, compared with saline-implanted control eyes. CONCLUSIONS AND CLINICAL RELEVANCE: Micro-osmotic pumps were implanted and removed easily from standing horses and were not associated with complications during the 7-day treatment period. Therefore, subconjunctivally implanted micro-osmotic pumps can potentially be used when treating ophthalmic disease in horses.