CD3 (immunology)

File:TCRComplex.pngThe T cell receptor complex with TCR-α and TCR-β chains (top), ζ-chain accessory molecules (bottom) and CD3 (represented by CD3γ, CD3δ and two CD3ε). CD3d molecule, delta

Identifiers
Symbol| CD3D
Alt. symbols| T3D
Entrez| 915
HUGO| 1673
OMIM| 186790
PDB| 1XIW
RefSeq| NM_000732
UniProt| P04234
Other data
Locus| Chr. 11 q23
CD3e molecule, epsilon

Identifiers
Symbol| CD3E
Entrez| 916
HUGO| 1674
OMIM| 186830
RefSeq| NM_000733
UniProt| P07766
Other data
Locus| Chr. 11 q23
CD3g molecule, gamma

Identifiers
Symbol| CD3G
Entrez| 917
HUGO| 1675
OMIM| 186740
RefSeq| NM_000073
UniProt| P09693
Other data
Locus| Chr. 11 q23

In immunology, the CD3 (cluster of differentiation 3) T cell co-receptor helps to activate both the cytotoxic T cell (CD8+ naive T cells) and also T helper cells (CD4+ naive T cells). It consists of a protein complex and is composed of four distinct chains. In mammals, the complex contains a CD3γ chain, a CD3δ chain, and two CD3ε chains. These chains associate with the T-cell receptor (TCR) and the ζ-chain (zeta-chain) to generate an activation signal in T lymphocytes. The TCR, ζ-chain, and CD3 molecules together constitute the TCR complex.

## Contents

* 1 Structure
* 2 Regulation
* 3 As a drug target
* 4 Immunohistochemistry
* 5 References
* 6 Further reading
* 7 External links

## Structure

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The CD3γ, CD3δ, and CD3ε chains are highly related cell-surface proteins of the immunoglobulin superfamily containing a single extracellular immunoglobulin domain.

Containing aspartate residues, the transmembrane region of the CD3 chains is negatively charged, a characteristic that allows these chains to associate with the positively charged TCR chains.[1]

The intracellular tails of the CD3 molecules contain a single conserved motif known as an immunoreceptor tyrosine-based activation motif or ITAM for short, which is essential for the signaling capacity of the TCR.

The intracellular tails of the ζ chain contain 3 ITAM motifs.

## Regulation

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Phosphorylation of the ITAM on CD3 renders the CD3 chain capable of binding an enzyme called ZAP70 (zeta associated protein), a kinase that is important in the signaling cascade of the T cell.

## As a drug target

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Because CD3 is required for T cell activation, drugs (often monoclonal antibodies) that target it are being investigated as immunosuppressant therapies (e.g., otelixizumab) for type 1 diabetes and other autoimmune diseases.

## Immunohistochemistry

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CD3 is initially expressed in the cytoplasm of pro-thymocytes, the stem cells from which T-cells arise in the thymus. The pro-thymocytes differentiate into common thymocytes, and then into medullary thymocytes, and it is at this latter stage that CD3 antigen begins to migrate to the cell membrane. The antigen is found bound to the membranes of all mature T-cells, and in virtually no other cell type, although it does appear to be present in small amounts in Purkinje cells.

This high specificity, combined with the presence of CD3 at all stages of T-cell development, makes it a useful immunohistochemical marker for T-cells in tissue sections. The antigen remains present in almost all T-cell lymphomas and leukaemias, and can therefore be used to distinguish them from superficially similar B-cell and myeloid neoplasms.[2]

## References

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1. ↑ Kuby J, Kindt TJ, Goldsby RA, Osborne BA (2007). Kuby Immunology. San Francisco: W.H. Freeman. ISBN 1-4292-0211-4.
2. ↑ Leong AS, Cooper K, Leong FJ (2003). Manual of Diagnostic Cytology (2nd ed.). Greenwich Medical Media, Ltd. pp. 63–64. ISBN 1-84110-100-1.

## Further reading

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* Shiv P, Abul KA, Andrew W (2011). Cellular and Molecular Immunology: with STUDENT CONSULT Online Access. Philadelphia: Saunders. ISBN 1-4377-1528-1.

## External links

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* Media related to [[commons:Lua error in Module:WikidataIB at line 428: attempt to index field 'wikibase' (a nil value).|Lua error in Module:WikidataIB at line 428: attempt to index field 'wikibase' (a nil value).]] at Wikimedia Commons
* CD3+Antigens at the US National Library of Medicine Medical Subject Headings (MeSH)
* Mouse CD Antigen Chart
* Human CD Antigen Chart

* v
* t
* e

Transmembrane receptors: immunoglobulin superfamily immune receptors

Antibody receptor:
Fc receptor|

| Epsilon (ε)|

* FcεRI
* (FcεRII is C-type lectin)

|

Gamma (γ)|

* FcγRI
* FcγRII
* FcγRIII
* Neonatal

Alpha (α)/mu (μ)|

* FcαRI
* Fcα/μR

Secretory|

* Polymeric immunoglobulin receptor

Antigen receptor|

| B cells|

| Antigen receptor|

* BCR

|

Co-receptor|

| stimulate:|

* CD21/CD19/CD81

|

inhibit:|

* CD22

Accessory molecules|

* Ig-α/Ig-β (CD79)

T cells|

| Ligands|

* MHC
* MHC class I
* MHC class II

|

Antigen receptor|

* TCR: TRA@
* TRB@
* TRD@
* TRG@

Co-receptors|

* CD8 (with two glycoprotein chains CD8α and CD8β)
* CD4

Accessory molecules|

* CD3
* CD3γ
* CD3δ
* CD3ε
* ζ-chain (also called CD3ζ and TCRζ)

Cytokine receptor|

* see cytokine receptors

Killer-cell IG-like receptors|

* KIR2DL1
* KIR2DL2
* KIR2DL3
* KIR2DL4
* KIR2DL5A
* KIR2DL5B
* KIR2DS1
* KIR2DS2
* KIR2DS3
* KIR2DS4
* KIR2DS5
* KIR3DL1
* KIR3DL2
* KIR3DL3
* KIR3DS1

Leukocyte IG-like receptors|

* LILRA1
* LILRA2
* LILRA3
* LILRA4
* LILRA5
* LILRA6
* LILRB1
* LILRB2
* LILRB3
* LILRB4
* LILRB5
* LILRA6
* LILRA5

* v
* t
* e

Proteins: clusters of differentiation (see also list of human clusters of differentiation)

1-50|

* CD1
* a-c
* 1A
* 1D
* 1E
* CD2
* CD3
* γ
* δ
* ε
* CD4
* CD5
* CD6
* CD7
* CD8
* a
* CD9
* CD10
* CD11
* a
* b
* c
* d
* CD13
* CD14
* CD15
* CD16
* A
* B
* CD18
* CD19
* CD20
* CD21
* CD22
* CD23
* CD24
* CD25
* CD26
* CD27
* CD28
* CD29
* CD30
* CD31
* CD32
* A
* B
* CD33
* CD34
* CD35
* CD36
* CD37
* CD38
* CD39
* CD40
* CD41
* CD42
* a
* b
* c
* d
* CD43
* CD44
* CD45
* CD46
* CD47
* CD48
* CD49
* a
* b
* c
* d
* e
* f
* CD50

51-100|

* CD51
* CD52
* CD53
* CD54
* CD55
* CD56
* CD57
* CD58
* CD59
* CD61
* CD62
* E
* L
* P
* CD63
* CD64
* A
* B
* C
* CD66
* a
* b
* c
* d
* e
* f
* CD68
* CD69
* CD70
* CD71
* CD72
* CD73
* CD74
* CD78
* CD79
* a
* b
* CD80
* CD81
* CD82
* CD83
* CD84
* CD85
* a
* d
* e
* h
* j
* k
* CD86
* CD87
* CD88
* CD89
* CD90
* CD91 \- CD92
* CD93
* CD94
* CD95
* CD96
* CD97
* CD98
* CD99
* CD100

101-150|

* CD101
* CD102
* CD103
* CD104
* CD105
* CD106
* CD107
* a
* b
* CD108
* CD109
* CD110
* CD111
* CD112
* CD113
* CD114
* CD115
* CD116
* CD117
* CD118
* CD119
* CD120
* a
* b
* CD121
* a
* b
* CD122
* CD123
* CD124
* CD125
* CD126
* CD127
* CD129
* CD130
* CD131
* CD132
* CD133
* CD134
* CD135
* CD136
* CD137
* CD138
* CD140b
* CD141
* CD142
* CD143
* CD144
* CD146
* CD147
* CD148
* CD150

151-200|

* CD151
* CD152
* CD153
* CD154
* CD155
* CD156
* a
* b
* c
* CD157
* CD158 (a
* d
* e
* i
* k)
* CD159
* a
* c
* CD160
* CD161
* CD162
* CD163
* CD164
* CD166
* CD167
* a
* b
* CD168
* CD169
* CD170
* CD171
* CD172
* a
* b
* g
* CD174
* CD177
* CD178
* CD179
* a
* b
* CD180
* CD181
* CD182
* CD183
* CD184
* CD185
* CD186
* CD191
* CD192
* CD193
* CD194
* CD195
* CD196
* CD197
* CDw198
* CDw199
* CD200

201-250|

* CD201
* CD202b
* CD204
* CD205
* CD206
* CD207
* CD208
* CD209
* CDw210
* a
* b
* CD212
* CD213a
* 1
* 2
* CD217
* CD218 (a
* b)
* CD220
* CD221
* CD222
* CD223
* CD224
* CD225
* CD226
* CD227
* CD228
* CD229
* CD230
* CD233
* CD234
* CD235
* a
* b
* CD236
* CD238
* CD239
* CD240CE
* CD240D
* CD241
* CD243
* CD244
* CD246
* CD247 \- CD248
* CD249

251-300|

* CD252
* CD253
* CD254
* CD256
* CD257
* CD258
* CD261
* CD262
* CD263
* CD264
* CD265
* CD266
* CD267
* CD268
* CD269
* CD271
* CD272
* CD273
* CD274
* CD275
* CD276
* CD278
* CD279
* CD280
* CD281
* CD282
* CD283
* CD284
* CD286
* CD288
* CD289
* CD290
* CD292
* CDw293
* CD294
* CD295
* CD297
* CD298
* CD299

301-350|

* CD300A
* CD301
* CD302
* CD303
* CD304
* CD305
* CD306
* CD307
* CD309
* CD312
* CD314
* CD315
* CD316
* CD317
* CD318
* CD320
* CD321
* CD322
* CD324
* CD325
* CD326
* CD328
* CD329
* CD331
* CD332
* CD333
* CD334
* CD335
* CD336
* CD337
* CD338
* CD339
* CD340
* CD344
* CD349
* CD350

* v
* t
* e

Cluster of differentiation by lineage

Lymphoid|

| B cell|

* Pre-B cell: CD10/CALLA
* CD79A

* mature: CD19
* CD20
* CD21/CR2
* CD23/FcεRII
* CD127
* CD40

* plasma cell: CD38
* CD138

|

T/NK|

| T cell|

* Pan-T antigens: CD3
* CD7

* CD1
* CD4
* CD8
* CD13
* CD18
* CD26
* CD27
* CD28

|

NK cell|

* CD16
* CD56/NCAM
* CD57

All|

* CD2

All|

* CD5

Myeloid|

| CFU-GM/
Myelomonocyte|

* CD11c
* CD14
* CD15
* CD31
* CD64
* CD68

|

MEP|

| CFU-Meg|

* CD34/CD36
* CD42
* CD41/CD61

|

CFU-E|

* CD36
* CD71

All (pan-myeloid)|

* CD13
* CD33

Stem cell|

* CD34

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