Immunological and histopathological changes in alkali burn-induced ocular surface pannus: Implication on success vs. failure of SLET

PURPOSE: This study aimed to investigate the histopathological and immunological characteristics of human alkali burn ocular surface pannus in successful and failed cases of simple limbal epithelial transplantation (SLET). METHODS: Paraffin embedded pannus sections of limbal stem cell deficiency (LSCD) patients who underwent simple limbal epithelial transplantation were obtained from pathology. Samples included both cases of SLET failure (n = 12) and success (n = 7). Histological features were assessed using Hematoxylin-Eosin and Periodic acid-Schiff staining while infiltrated immune cells were characterised using immunohistochemistry. Data were represented as mean or median with the interquartile range and standard deviation. Multiple comparisons of means by linear mixed effect model with Tukey contrast and Bonferroni method were used. RESULTS: Conjunctivalization of the cornea that led to fibrous pannus formation was confirmed by the presence of CK19+ and CK3/12- cells. The median percentage of immune cell infiltrates like T-cells (CD3; success (9 %; IQR-9.2) vs. failure (23.5 %; IQR-10.2), (CD5; success (2.2 %; IQR-3) vs. failure (13.4 %; IQR-18.3), B-cells (CD20; success (3.2 %; IQR-3.2) vs. failure (4.1 %; IQR-5.5), antigen presenting cells (co-stimulatory CD40; success (7.8 %; IQR-8.9) vs. failure (16.4 %; IQR-7.1), and plasma cells (CD138; success (1.1 %; IQR-2.1) vs. failure (3.6 %; IQR-3.5) were identified in the pannus. CONCLUSIONS: This study highlights a significantly higher infiltration of immune cells in the pannus and surrounding ocular tissue in cases of SLET failure compared to successful outcomes. These findings suggest that, strategies to reduce immune infiltration such as immunotherapy, corticosteroids, or amniotic membrane grafting should be considered prior to SLET to improve the success of limbal transplant surgery.