Dissemination of T Lymphocytes and Potential Immune‐Escape Mechanisms of Bovine Skin Squamous Cell Carcinoma Regarding
MHC
‐1 and
PD
‐
Sabah M. Sameen, Waseem Al‐Jameel ABSTRACT
Background
Bovine skin squamous cell carcinoma (SCC) is a malignant neoplasm in cattle triggered by sunlight exposure. Immune escape drives tumour survival and progression. Previous findings in humans have emphasised the prognostic value of immune checkpoint marker (PDL‐1), major histocompatibility complex (MHC‐1) and cytotoxic CD8 T cells in the context of cancer immune escape.
Objectives
We examined the distribution of CD8 + T cells and the possible immune‐escape mechanisms of SCC in relation to PD‐L1 and MHC‐1 expression and correlated marker expression with tumour grade.
Animals
Twenty samples of bovine skin SCC were collected between 2025 and 2026.
Materials and Methods
Histopathological evaluation, including grading, was performed on SCC samples. Immunohistochemical examination was performed for all three proteins in relation to histological grade, substantiated by the mRNA levels of MHC‐1 and PD‐L1.
Results
We observed a significant relationship between PD‐L1 expression and grade, increasing from 33% in well‐differentiated SCC to 100% in moderately and poorly differentiated SCC. PD‐L1 mRNA levels in well‐ and moderately differentiated SCC remained comparable, whereas poorly differentiated SCC exhibited a significant upregulation. MHC‐1 showed a significant grade‐dependent decline, decreasing from 83% in well differentiated to complete loss in poorly differentiated. This progressive protein loss was corroborated at the transcriptional level. High CD8 T‐cell levels were observed in 83% of well‐differentiated SCC, with complete absence in poorly differentiated SCC.
Conclusions and Clinical Relevance
This study emphasises the importance of PD‐L1, MHC‐1 and CD8 T‐cell biomarkers as prognostic indicators in SCC. High PD‐L1, low MHC‐1 and CD8 represent potential immune‐escape mechanisms for bovine SCC.