CD19

Summary

CD19 expressed through most stages of B-cell development and is considered a pan B-cell marker i.e. present at early B-cell commitment until plasma cell stage

Normal expression and function

CD19 forms part of the normal B-cell receptor, and plays a major role in the recruiting and activating signalling proteins involved in B-cell activation. it reliably expressed by most normal B lymphocytes and also by follicular dendritic cells. Expression is acquired very early during normal B-cell development and tends to increase as B cells mature before becoming lost during the transition to plasma cells.

Diagnostic role

• CD19 is very useful in the confirmation of B-lineage of normal and malignant b cells although not etirely specific
• Note however that expression may be absent in very early cases of all and that CD19 and is absent on plasma cells and in some cases of DLBCL
• The level of expression may be helpful with high levels in hairy cell leukaemia with relatively low levels of expression in CLL
• CD19 is a fairly common aberrant marker in AML particularly cases with the t 8;21 cytogenetic lesion

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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%	80-100%**	80-100%	<5%	<5%	40-80%	80-100%

Notes: **While a good marker of B lineage it may not be expressed in more primitive phenotype ALL, there is also a recognised abberrant expression in AML (particularly cases with t)8;21)

Expression in mature B cell neoplasms
CLL	MCL	FL	MZL	HCL	DLBCL	LPL	PCL
80-100%*	80-100%	80-100%	80-100%**	80-100%**	40-80%	80-100%	5-20%*

Notes: Level of expression is important with low expression in CLL* and typically high expression in HCL

Expression in mature T cell neoplasms*
ATLL	CTCL/Sezary	T-PLL	T-LGL	NK-LGL
<5%	<5%	<5%	<5%	<5%

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