TTR and glaucoma: To evaluate possible age-related changes that could confound the comparisons, serum samples from DBA/2J mice not developing glaucoma (DBA/2J_NG, 21% of the total number of DBA/2J mice) were used as controls for the analysis of five of the proteins (i.e., APOA1, APOA4, C3, C4a, and TTR).