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Reviewer: Nat Pernick, M.D. (see Reviewers page)
Revised: 14 April 2013, last major update April 2013
Copyright: (c) 2002-2013, PathologyOutlines.com, Inc.


● HLA-DR is a MHC (major histocompatibility complex) class II cell surface receptor encoded by human leukocyte antigen complex on 6p21.31 (Wikipedia-HLA-DR)
● Antigen presenting cells use HLA-DR molecules to present protein fragments (processed antigen) to T cells, a key event in induction of T cell responses (PLoS One 2012;7:e31483)

Clinical features

● Involved in several autoimmune conditions, disease susceptibility and disease resistance (Scand J Immunol 2011;74:603), including idiopathic dilated cardiomyopathy (Mol Biol Rep 2012;39:221), hepatits B persistence (World J Gastroenterol 2012;18:3119)
● HLA-DR on Tregs is a good marker for HIV1 viral replication and disease progression (Chin Med J (Engl) 2011;124:2340)
● Hypoxia increases membrane and secreted HLA-DR in endothelial cells, rendering them T-cell activators; may be important in transplants (which have preoperative ischemic periods) and graft rejection (Transpl Int 2011;24:1018)
● HLA-DRB1 mismatches are significant risk factor for kidney transplant rejection, although may be difficult to find matched donors (Arch Surg 2011;146:824)
● Decrease in density of HLA-DR+ cells occurs faster in corneas stored in organ culture than under hypothermic conditions; may prolong graft survival (Ophthalmic Res 2012;47:39)


Various diagrams

Micro images

Cervix: squamous cell carcinoma (figure A)

Diffuse large B cell lymphoma: HLA-DR shows membranous staining (figure D)

Skin: atopic eczema lesions

Skin scar: coexpression of CD34 and HLA-DR

Positive staining - normal

● Basophils (immature), osteoblasts
● Antigen presenting cells (B cells, dendritic cells, macrophages, monocytes)
● Precursor T cells and CD4+ T cells
● Liver: bile ductules
● Thymus

Positive staining - disease

● AML: M0-M6 (some variability); also AML, with myelodysplastic related changes, recurrent genetic abnormalities; acute basophilic leukemia, acute panmyelosis with myelofibrosis, transient myeloproliferative disorder of Down’s syndrome (80%)
● Breast: medullary carcinoma
● Esophagus: Crohn's disease
● Langerhans cell histiocytosis
● Lymphomas: adult T cell leukemia/lymphoma (HTLV1+) (frequent), B-ALL, blastic plasmacytoid dendritic cell neoplasm, extranodal NK/T-cell lymphoma nasal type, primary effusion, SLL/CLL
● Thyroid: Grave's disease (thyrocytes and lymphocytes)

Negative staining

● Acute promyelocytic leukemia (usually, Am J Clin Pathol 2011;135:76)

End of Stains > HLA-DR (Ia)

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