Major histocompatibility complex class II (MHC II) presenting tumor-derived peptides (MHC II-peptide complex)

Major histocompatibility complex class II (MHC II) molecules are heterodimeric cell surface proteins that play a pivotal role in the adaptive immune system by presenting exogenous peptides to CD4+ T helper cells (Wikipedia; AACR Journals, 2021). While traditionally associated with professional antigen-presenting cells (APCs) like dendritic cells and B cells, MHC II can also be expressed by certain tumor cells, where it is referred to as tumor-specific MHC II (tsMHC-II) (Cancer Biology & Medicine, 2023; NIH). In the context of oncology, these molecules present tumor-derived peptides, including neoantigens arising from somatic mutations or tumor-associated antigens like MAGE-A3 (Nature, 2017; Journal of Clinical Oncology, 2017). This presentation is essential for the activation of CD4+ T cells, which coordinate the anti-tumor response by secreting pro-inflammatory cytokines such as IFN-gamma and providing necessary help to CD8+ cytotoxic T cells (AACR Journals, 2021; NIH, 2018). Therapeutic targeting of MHC II-peptide complexes involves several modalities, including personalized neoantigen vaccines (e.g., Neo-PV-01) designed to elicit CD4+ T cell responses and adoptive T-cell therapies using TCR-engineered T cells (TCR-T) (Kactus Bio; Journal of Clinical Oncology, 2017). Challenges in targeting these complexes include the high polymorphism of HLA genes and the low density of specific pMHC complexes on the cell surface (Frontiers in Immunology, 2020). Furthermore, tumors often evade immune detection by downregulating MHC II expression through the suppression of the CIITA transactivator (NIH, 2023). Despite these challenges, MHC II-restricted targets are increasingly recognized as critical for achieving durable clinical responses in cancer immunotherapy (AACR Journals, 2021).

Other names

HLA class II-peptide complexMHC II-neoantigen complexTumor-specific MHC II-peptide complexpMHC-IItsMHC-II

Activation of CD4+ T cells and induction of anti-tumor immunity through the recognition of tumor-specific peptides presented on MHC class II molecules, leading to Th1 differentiation and support for CD8+ cytotoxic T cell responses.