C1r-C1s-C1inhibitor (C1rs-C1inh) complex measurements in tears of patients before and after penetrating keratoplasty

Purpose. The aim of this pilot study was to determine the presence of complement activation products in tears from pre- and postkeratoplasty eyes and the fellow eyes in order to investigate the activation of the classical and alternative pathways of the complement system in the early postkeratoplasty period. Methods. Tear samples from both eyes of 19 prekeratoplasty patients were tested. From 10 patients, samples were taken before operation, one week and 3 weeks after penetrating keratoplasty. Only baseline and 1 weak samples, and baseline and 3 week samples were available from 5 and 2 patients, respectively, while only baseline tear samples were collected from 2 patients. Tear concentration of two complement activation products, C1rs-C1inh and C3bBbP were determined by enzyme-linked immunosorbent assay. Results. There was no difference (p = 0.339) between baseline samples of the eyes waiting for operation (0.93 ± 0.51 AU/ml, mean ± SEM) and the fellow eyes (0.33 ± 0.33 AU/ml) in respect of mean C1rs-C1inh complex concentration. The one-week samples of the operated eyes revealed significantly (p = 0.006) elevated levels of C1rs-C1inh complexes (18.8. ± 6.37 AU/ml), compared to their baseline samples (1.18 ± 0.64 AU/ml), whereas the one-week values of the fellow eyes did not differ from the baseline values. Compared to the increased one-week values, the three-week values decreased to the baseline values in the operated eyes. C3bBbP could be detected in 3/68 tear samples. Conclusions. In our study we demonstrated the increased concentration of C1rs-C1inh complex in several tear samples taken early after human penetrating keratoplasty. These findings provide direct evidence that the classical pathway of complement may be activated in the early postoperative period after penetrating keratoplasty.