Figure 2.

Degradation of LF, Cys C, and sIgA by CTSS occurs in tears from SS patients but not in tears from healthy controls. Tears obtained from SS patients and healthy controls were collected on Schirmer’s strips and were eluted in CTSS sample buffer. For LF degradation, tear samples were supplemented with 2.6 µg of recombinant LF only. For Cys C degradation, tear samples were supplemented with 2.5 µg Cys C and 2.6 µg LF. For sIgA degradation, tear samples were supplemented with 5 µg of purified sIgA. All supplemented tear samples were treated without or with recombinant CTSS equivalent to 18,000 RFU/10 mg tear protein for 4 hr at 37 °C. Equal amounts of recombinant LF, Cys C, and purified sIgA in PBS were used as controls. LF (A) and Cys C (B) loss by degradation was evaluated by Western blotting and densitometry as shown for LF in (C) and Cys C in (D). sIgA was blotted with both anti J-chain antibody (E) to detect multimeric IgA forms and with anti-IgA (F) antibody to detect monomeric IgA on the same gel. Densitometry is shown in (G) and (H), respectively. For quantitation, n = 6 for LF, n = 3 for Cys C and n = 4 for sIgA. Bars show SEM; *p < 0.05, **p < 0.01. Representative blots are shown. Full length blots are shown in Supplementary Figs 2 and 3.