Mass Spectrometry: Peptides were analyzed with a Waters NanoAcquity liquid chromatograph (LC) paired with a Q-Exactive mass spectrometer (Thermo Scientific). 200 ng of peptides were injected into the LC system equipped with a peptide BEH C18 100 mm column containing 1.7 mm particles (Waters; Milford, MA). Peptides were separated over a 48-minute gradient with a flow rate of 0.9 µL/min with a two-solvent system where solvent A was water containing 0.1% FA and solvent B was ACN containing 0.1% FA. The following linear gradient was used for all samples: 4% B for 0-8 min, 4-7% B from 8-10 min, 7-33% B from 10-30 min, 33-90% B from 30-33 min, 90% B until 36 min, 90-4% B for 1 min, and reequilibration at 4% B from 37-48 min. The mass spectrometer settings were identical to those described previously. Database Searching (PEAKS): Raw data files were searched using PEAKS Online X build 1.4.2020-10-21 (Bioinformatics Solutions, Waterloo, ON, Canada) using the current Homo sapiens Uniprot database (downloaded June 27, 2022), with the MUC16 entry (Accession ID: Q8WXI7, 14,152 amino acids) replaced with the version from the 2016 SwissProt database (22,152 amino acids) for the human serum samples, and the current Gallus gallus Uniprot database (downloaded June 24, 2022) for the chicken protein samples. The digestion enzyme was set to trypsin with a maximum of two missed cleavages. Precursor mass tolerance was set to 10 ppm and fragment mass error tolerance was set to 0.02 Da. Carbamidomethylation of C was added as a global modification, and deamidation of N and Q, oxidation of M, pyro-glu conversion from E and Q, and sodium adduction were set as variable modifications. A peptide FDR was set to 1% and protein -10log P was set to ³ 20. Peptides of length 6 to 45 amino acids were considered, and common contaminants (including keratin) were filtered out. Two or more unique peptides were required for protein identification.