HLA-I -Human leukocyte antigen

The antitumor effect of immunotherapy with immune checkpoint inhibitors (checkpoint inhibitors, anti PD-1, anti PDL-1 and anti CTLA-4) is related to CD8+ T cells. Cancer cell recognition by CD8+ T cells is achieved by HLA-I (Human Leukocyte Antigens) molecules that present the endogenous antigens to the immune system.
The HLA class I complex is subdivided into three genetic loci HLA-A, HLA-B and HLA-C. When a patient’s HLA-I is homozygous at least one genetic locus, the patient is expected to present less diverse tumor neoantigens on T cells compared to patients who are heterozygous at all three genetic loci. Somatic loss of heterozygosity at HLA-I is associated with reduced response to immunotherapy.