Total protein concentration and T-cell suppression activity of aqueous humour before and after penetrating keratoplasty

We wished to determine whether immune privilege parameters assayed in aqueous humour (AqH) are relevant to the fate of penetrating keratoplasty (PK) in humans.

AqH was collected in 28 patients before PK (prospective cohort), in 6 patients with no history of graft rejection undergoing cataract surgery after PK (acceptors), in another 6 patients undergoing treatment of an acute endothelial immune reaction (rejectors), and in 65 controls undergoing uncomplicated cataract extraction. AqH was tested for total protein concentration and the ability to suppress T-cell activation.

AqH protein concentrations of acceptors and rejectors post-PK were elevated (2.7 ± 0.8 and 2.7 ± 0.7 mg/ml, respectively) compared with pre-PK AqH level and cataract controls (1.0 ± 0.1 mg/ml, P = 0.01). All AqH samples suppressed T-cell activation, irrespective of source and timing of AqH removal.

Assays of immune privilege markers in AqH suggest that PK surgery may result in a sustained loss of integrity of the blood-aqueous barrier. Although trends were evident, values of immune privilege markers determined pre- and post-PK were not statistically significantly different between the study groups. However, further prospective studies determining additional immune privilege markers have to be conducted in order to find out whether these markers might serve as predictive parameters for immune reactions following PK.