Investigating MHC Class II Expression, Localisation and Antigen Presentation in Human Melanoma Cells.

Major histocompatibility complex (MHC) class II molecules are crucial for adaptive immunity, as they present antigens to CD4(+) T lymphocytes to drive their activation. Although MHC class II molecules are primarily on the cell surface of professional antigen-presenting cells, they can also be expressed in melanoma, where they are implicated in neoantigen presentation and immune evasion. This study investigates the expression and localisation of MHC class II molecules, specifically HLA-DR and HLA-DP, in a human melanoma cell line. The results show that HLA-DR and HLA-DP are constitutively expressed independent of IFN-γ treatment. Post translational modification patterns, including glycosylation and sialylation, provide insights into HLA-DR and HLA-DP trafficking, stability, and role in antigen presentation. The study also examines accessory proteins involved in MHC class II processing, with a focus on the Invariant chain (CD74). Results support its involvement in the regulation of MHC class II maturation in human melanoma cells. Additionally, the study investigates candidate proteins with a potential role in MHC class II presentation, providing evidence of their possible interactions with MHC class II in melanoma through immunoprecipitation and mass spectrometry. These findings enhance our understanding of the MHC class II antigen presentation pathway in human melanoma and highlight its potential as a target for immunotherapeutic strategies.