Pathology Outlines

CD Markers
CD45

Topic Completed: 1 October 2013

Minor changes: 12 August 2019

Revised: 14 December 2018, last major update October 2013

Copyright: (c) 2003-2018, PathologyOutlines.com, Inc.

PubMed Search: CD45[title]

Related topics: CD45RO, CD45RA, CD45RB, CD45RC

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Table of Contents

Cite this page: Pernick N. CD45. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cdmarkerscd45.html. Accessed May 28th, 2020.

Definition / general

Commonly used marker of hematopoietic cells except erythrocytes and platelets; plays a major role in immune system
Also called leukocyte common antigen (LCA), protein tyrosine phosphatase (References: OMIM #151460)

Pathophysiology

High molecular weight transmembrane protein with intrinsic tyrosine phosphatase activity
Heavily glycosylated and expressed at high levels on nucleated hematopoietic cells
Disruption of the equilibrium between protein tyrosine kinase and phosphatase activity (from CD45 and others) can result in immunodeficiency, autoimmunity or malignancy (Immunol Rev 2009;228:288)
An essential regulator of T and B cell antigen receptor-mediated activation
Also required for thymic selection
Major component of glycocalyx

Clinical features

Different subsets of hematopoietic cells express different CD45 isoforms due to variable exon splicing, which can change in response to cytokines:

CD45RA: naive / resting T cells, medullary thymocytes
CD45RO: memory / activated T cells, cortical thymocytes
Also CD45RB and CD45RC

Loss of CD45 mutations cause severe combined immunodeficiency-autosomal recessive, T cell negative, B cell positive and NK cell positive (OMIM #608971); patients have a defect in B/T cell development, lymphopenia and deficiency in humoral and cell-mediated immunity
77C to G mutation may increase intensity of T cell receptor signaling (J Immunol 2006;176:931) and cause some cases of systemic sclerosis (Genes Immun 2003;4:168), multiple sclerosis (controversial, Nat Genet 2000;26:495) and autoimmune hepatitis (Genes Immun 2003;4:79)
Loss of CD45 activity in lymphocytes of elderly may cause T cell dysfunction (Mech Ageing Dev 2003;124:191)
Necrotic lymphomas are still CD45+, but occasional necrotic carcinomas may also be CD45+ (Am J Clin Pathol 1998;110:641)

Uses by pathologists

Confirm presence of inflammatory cells, including intestinal intraepithelial lymphocytes (Arch Pathol Lab Med 2002;126:897)
Confirm hematopoietic nature of tumors
May assist in classification of lymphomas and leukemias (Am J Clin Pathol 1998;110:797)

Microscopic (histologic) images

Images hosted on PathOut server:

Nodular lymphocyte
predominant
Hodgkin lymphoma

Left: leukemia cutis; right: myeloid sarcoma of fibula

Leukemic vasculitis in the
context of leukemia cutis,
in a patient with atypical
chronic myeloid leukemia

Images hosted on other servers:

Normal:

Small intestine

Splenic lymphocytes

Thymus

Lymphoma:

Immunoreactivity of
the lymphoma cells for
cytokeratin (A) and CD20
(C) but not CD45 (B)

Left: diffuse large B cell lymphoma - urine cytology; middle: diffuse large B cell lymphoma - H&E (fig 7);
right: Hodgkin-Reed-Sternberg cells are CD45- (fig 3C)

Other:

Lymphoepithelioma-like carcinomas: tumor cells are CD45- but infiltrating lymphocytes are CD45+
(left: stomach; right: cervix)

Positive staining - normal

Hematopoietic cells, including basophils, granulocytes, lymphocytes, macrophages / histiocytes, mast cells, monocytes and plasma cells; NOT mature red blood cells and their immediate progenitors, platelets or megakaryocytes
Dendritic cells, fibrocytes (J Immunol 1998;160:419) and medullary thymocytes

Positive staining - disease

AML (Am J Clin Pathol 1998;109:211), anaplastic large cell lymphoma (usually, Am J Clin Pathol 2003;119:205, Hum Pathol 1990;21:624), B and T cell lymphomas (most), CD4(+) CD56(+) lineage-negative malignancies (Am J Surg Pathol 2005;29:1274) and dendrocytoma (Am J Surg Pathol 1990;14:867)
Giant cell tumor of tendon sheath (Mod Pathol 1995;8:155), histiocytic sarcoma (Am J Surg Pathol 1998;22:1386), inflammatory pseudotumors (some, Am J Clin Pathol 1996;105:430) and interdigitating dendritic cell sarcoma (variable, Am J Clin Pathol 2001;115:589)
Leukemia cutis, lymphocyte predominant Hodgkin’s lymphoma (Am J Surg Pathol 1994;18:526), myeloid sarcoma (Am J Surg Pathol 1993;17:1011) and mycobacterial spindle cell pseudotumor in lymph nodes
Plasma cell neoplasms (variable, Blood Cells Mol Dis 2004;32:293), post-transplant lymphoproliferative disorders (Am J Clin Pathol 2004;121:246), preB lymphoblastic lymphoma (low, Am J Clin Pathol 2009;132:940) and primary effusion lymphoma (Am J Surg Pathol 2004;28:1401)
Reticulohistiocytoma (variable, Am J Surg Pathol 2006;30:521), transient myeloproliferative disorder of Down's syndrome (Am J Clin Pathol 2001;116:204)
Candida albicans yeast forms (Am J Clin Pathol 2000;113:59)
Rarely carcinomas (undifferentiated / neuroendocrine, Mod Pathol 1998;11:1204 or necrotic)

Negative staining

Red blood cells and their immediate progenitors, megakaryocytes, osteoblasts and platelets
Epithelial tumors (although necrotic carcinomas may be CD45+, Am J Clin Pathol 1998;110:641), follicular dendritic cell sarcoma (Am J Clin Pathol 1995;103:90), germ cell tumors, melanoma, mesothelioma, multiple myeloma (CD45+ in 9% by flow cytometry, Am J Clin Pathol 2004;121:482, Am J Clin Pathol 2010;133:265) and sarcoma
Reed-Sternberg cells in classic Hodgkin’s lymphoma (Am J Pathol 1991;139:701)
Note that infiltrating lymphocytes in any disorder are typically CD45+, and they must be distinguished from tumor cells

Flow cytometry description

Images hosted on other servers:

Anaplastic large cell lymphoma

Transient myeloproliferative disorder
with erythroid differentiation in
Down’s syndrome (figure C)