CD2

Summary

CD2 is a pan t-cell marker. In diagnostic use it may be less reliable than CD3 for identification of T-cell lineage, since loss of CD2 expression is seen in some peripheral T-cell lymphomas, and aberrant expression in AML is recognised (particularly the APL subtype).

Normal expression and function

CD2 forms part of the T-cell receptor complex, mediating adhesion to accessory cells and assisting in the generation and control of intracellular signal transduction. Expression of CD2 is acquired during early T cell ontogeny, preceded by CD7 and cytoplasmic CD3 expression and is then retained through thymic maturation and by peripheral t cells. CD2 is also expressed only by a proportion of normal mast cells but is frequently expressed in systemic mastocytosis.

Diagnostic role

CD2 generally identifies T-cell lineage and is not expressed by normal B-cells

• In T-ALL and peripheral T-cell lymphomas CD2 may contribute to diagnosis, but loss of expression is recognised
• CD2 and CD7 are expressed by NK cells (in contrast to CD3) and may be used together with CD56 to identify NK cells

Other relevant information:

In systemic mastocytosis CD2 (with or without CD25) is expressed on the abnormal mast cell population, and in a proportion of cases CD25 may provide greater sensitivity and specificity

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SUMMARY TABLES

Note The colour and % refer to the proportion of cases expressing the marker. Additional comments on strength, or site of expression (if relevant) are given below the table. For full details of key click here. For further information about a particular disease state click <I> adjacent to the condition name

Expression in primitive cell types
AML	CMML	B ALL	BL	T ALL	ETP ALL	MPAL	Hgn
5-20%	5-20%	<5%	<5%	80-100%	80-100%	20-40%	<5%

Notes: CD2 tend not to be included on immunophenotyping routinely in primitive myeloid disorders, but has value as a contributary marker of T-lineage in difficult cases (e.g. MPAL or ETP-ALL). In AML expression may occur, and is a frequent finding APL; in CMML it can be considered a marker of atypical monocytes adding support to a diagnosis.

Expression in mature B cell neoplasms
CLL	MCL	FL	MZL	HCL	DLBCL	LPL	PCL
5-20%	?	20-40%	?	5-20%	?	?	?

Notes: The literature is limited, but CD2 may be expressed on some normal B cells at low level, and is found on at least some cases of mature B-LPD

Expression in mature T cell neoplasms*
ATLL	CTCL/Sezary	T-PLL	T-LGL	NK-LGL
80-100%	80-100%	80-100%	80-100%	80-100%

Notes: An expected antigen on mature neoplastic T-cells. It is generaly expressed on NK cells (in contrast to CD3 which should not be expressed.

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