HA-1 (minor histocompatibility antigen)

Class

Allogeneic TCR-T cell therapy

Pathway

T-cell receptor recognition of the blood-restricted HA-1 minor histocompatibility antigen, used post-allogeneic HSCT to eliminate residual leukemic cells

HA-1 is a minor histocompatibility antigen: a short peptide fragment, produced from a common gene, that differs between individuals because of a single amino-acid variant encoded by a genetic polymorphism. This peptide fragment is displayed on the cell surface, bound to a particular HLA-A molecule, but only by cells of blood and immune lineage, including leukemic cells derived from those lineages. In the setting of allogeneic hematopoietic stem cell transplantation, a donor lacking the HA-1 variant can supply T cells whose receptors recognize HA-1 as foreign when it appears on the recipient's cells. This underlies a therapeutic strategy: T cells engineered to express a receptor specific for HA-1 are administered after transplantation to seek out and destroy residual host leukemic cells carrying the antigen. Because HA-1 expression is largely confined to the blood-forming compartment rather than distributed across many tissue types, this approach aims to concentrate immune attack on leukemia and normal blood cells while sparing the broader graft-versus-host reactions associated with less tissue-restricted antigens. This mechanism is relevant to leukemias treated with stem cell transplantation, where relapse from surviving malignant cells remains a central clinical problem.