Fig 2: ELISA analyses of PIP in human tear samples. (A) Significant increase of the PIP concentration in tear samples from patients with dry eye disease (DED, n = 115) compared to healthy donors (n = 38). (B) PIP concentration in DED subgroups. There are increased PIP levels in tear samples of patients with aqueous deficient dry eye (ADDE, n = 19), evaporative dry eye (EDE, n = 48) and mixed dry eye (MDE, n = 48) compared to healthy subjects. Significantly increased PIP levels can only be seen in MDE compared to healthy subjects and in MDE compared to ADDE. (C) PIP concentration in analyzed groups divided by sex (women, n = 100 and men, n = 53). Significantly increased PIP levels can only be seen in MDE compared to healthy subjects. (D) PIP concentration in analyzed groups divided by age. There are significantly increased PIP levels in MDE compared to healthy subjects. One way anova and Dunn multiple comparison test, *p < 0.05, **/##p < 0.01.

Fig 3: Immunohistochemical analyses of prolactin inducible protein (PIP) in the human cornea (A) with corneal epithelium (CE), lacrimal gland (B) and eyelid (C) with Meibomian gland (MG). The antibody reaction is visible by the intracellular red reaction product. Pictures represent meaningful immunohistochemical analyses of sections obtained from 10 different cadavers for each tissue (n = 10). (A,B) and (C) Inlays show higher magnification. Nuclei are counterstained with hemalum (blue). Arrows and Arrowheads accentuate the reactivity localization.

Fig 4: RT-PCR analysis of PRLR and PIP gene expression in human ocular tissues and cell lines. The expression of ß-actin gene served as internal control for assessing integrity and stability of the transcribed cDNA. Cornea (C), lacrimal gland (LG), eye lid (L), undifferentiated human Meibomian gland epithelial cell line (Mu), differentiated human Meibomian gland epithelial cell line (Md), human corneal epithelium cell line hCTEpi (T), human corneal epithelium cell line HCE (HCE), negative control (N) positive control (P) for PRLR is submandibular gland and for PIP is testis. Pictures represent three independent experiments.