Differential Expression of Tear Lymphotoxin-Α, Immunoglobulin E, and Matrix Metalloproteinase-9 in Allergic Conjunctivitis-Associated Dry Eye

To evaluate the expression differences of tear lymphotoxin-α (LT-α), total immunoglobulin E (IgE), and matrix metalloproteinase-9 (MMP-9) in seasonal/perennial allergic conjunctivitis-associated dry eye (S/PAC-DE) and their clinical relevance, probing the underlying pathogenesis of S/PAC-DE. This study enrolled 37 S/PAC-DE patients, 23 dry eye (DE) patients, and 24 healthy controls (HC). Assessing the clinical parameters, tear LT-α, total IgE, MMP-9, and nine other inflammatory cytokines in the three groups. Correlations between tear cytokines and clinical parameters were also analyzed. Tear LT-α levels were significantly lower in S/PAC-DE compared to DE and HC groups. Tear total IgE, TNF-α, and MMP-9 levels were significantly upregulated in the S/PAC-DE group than those in the DE (all <i>p</i> &lt; 0.001) and HC groups (<i>p</i> = 0.005, <i>p</i> &lt; 0.001, and <i>p</i> = 0.048). In the S/PAC-DE group, total IgE was positively correlated with MMP-9 (<i>r</i> = 0.652, <i>p</i> = 0.008). Total IgE and LT-α were positively correlated in the DE group (<i>r</i> = 0.498, <i>p</i> = 0.016), while the two showed a negative correlation trend in the S/PAC-DE group (r=-0.272, <i>p</i> = 0.103). LT-α was positively correlated with tear film break-up time and negatively correlated with corneal fluorescein staining score in both the S/PAC-DE and DE groups. In the S/PAC-DE co-morbid state, the inhibition of tear LT-α expression and the upregulation of the pro-inflammatory cytokines total IgE, TNF-α, and MMP-9 may collectively contribute to the disruption of the ocular surface epithelial barrier, further promoting and exacerbating DE. Additionally, the differences in correlation between LT-α and total IgE in the S/PAC-DE and common DE patients may be related to the distinct ocular immune microenvironments.