CD79b

Summary

CD79b is a pan-B-cell marker expressed from early commitment to B-cell lineage then becoming lost during plasma cell differentiation; CD79b may be used as marker of B-cel lineage, but its more variable expression make it less useful than CD79a or CD19 in this context

The major diagnostic value of CD79b is its characteristically weak-expression in CLL

Normal expression and function

The two forms of CD79 (CD79a and CD79b) each associate directly with the immunoglobulin chains to control signalling from the B-cell receptor. Expression of both CD79a and CD79b is therefore acquired at early B-lymphocyte formation (initially in cytoplasm then membrane) and persist until plasma cell differentiation. However, while both CD79a and CD79b may be considered pan B-cell antigens, expression of CD79b is acquired later and is lost earlier than for CD79a.

Diagnostic role

• The most useful attribute of CD79b is its variable intensity of expression - in particular the characteristically weak intensity of expression of CD79b in CLL is often used as a diagnostic criterion

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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	Burkitt	T ALL	ETP ALL <I>	MPAL <I>	Hgns <I>
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: *low expression in CLL; **typically high expression in HCL; ***generally absent in PCs

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

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