minor histocompatibility protein HA-1 ([contains: minor histocompatibility antigen HA-1 (mHag HA-1)], HMHA1 KIAA0223)

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Function

GTPase activator for the Rho-type GTPases (putative)
precursor of the minor histocompatibility antigen HA-1
HA-1 is presented to the cell surface by MHC class 1 HLA-A*0201, but also by other HLA-A alleles; this complex specifically elicits donor-cytotoxic T-cell reactivity against hematologic malignancies after treatment by HLA-identical allogenic bone marrow transplantation; it induces cell recognition & lysis by CTL
HA-1 forms a complex with MHC class I HLA-A*0201

expressed on cells of the hematopoietic lineage
detected in dendritic cells & epidermal Langerhans cells
expressed in peripheral blood mononuclear cells
detected also in some solid tumors & tissues such as cancerous & non-cancerous tissue

during HLA-identical bone marrow transplantation, specifically, mismatching for mHag HA-1 (immunodominant), is associated severe GVHD
expressed in all leukemia/lymphoma cell lines
detected also in some solid tumors & tissues such as cancerous & non-cancerous tissue

the HA-1H allele is presented on the cell surface & recognized by CTL, whereas the HA-1R allele is poorly represented by HLA-A & non-immunogenic, although HA-1R allelic frequency is the highest

infusion of lymphocytes from mHag HA-1-negative donors results in a durable remission in mHag HA-1-positive patients with leukemia or multiple myeloma