Five proteins were identified as differentially expressed: serum albumin, lactotransferrin isoform 1, immunoglobulin gamma heavy chain C, major allergen Can f 1, and lysozyme C. High-molecular-weight proteins were upregulated in KCS, whereas low-molecular-weight proteins (<10 kDa, proline-rich protein-like components) were markedly reduced or absent. Here, C4BPA is linked to dry eye syndrome.