AW: Definition of monoclonal

Nebe, Thomas thomas.nebe at ikc.ma.uni-heidelberg.de
Fri Sep 25 10:32:01 EST 1998


Dear collegue,

let me try to answer. 
B-cells do not express light chains on their surface in their early (bone
marrow) and late (plasma cells) development.  In some NHL background due to
Fc receptor binding is so high, that light chain restriction is hard to
prove. In late stages cytoplasmic light chain restriction can be
demonstrated.  Monoclonality by light chains could be demostrated by
immunofixation methods in the serum as many NHL secrete small amounts of
immunoglobulin.  Of course a larger panel also depicts clonality but we
report the problem with the light chains. Molecular biology methods showing
clonality also help.
To your second question:
Polyclonal B cell lymphocytosis is seen in some HIV positives and are
polyclonal by surface light chain restriction.
The number of washing steps to remove serum immunoglobulins should be
validated in each laboratory. Minimum is three in our hands and four is
better.  Blocking with serum from the species where the light chain reagent
is derived from is a prerequisite.  So in expansion of immature B cells that
are kappa/lamda negative will not be recognized.  These will be seen in
repopulation phases after immunosuppression and regularily in the normal
bone marrow.
In conclusion monoclonality depends on performance and limitation to flow
cytometry.  Three colour combinations like kappa/CD19/CD20 or kappa/CD19/CD5
better resolve a subset of abnormal B cells in a mixture with normal B cells
(suited eg. for bone marrow, leaky or residual NHL). I already mentioned the
autogating software of Hans-Dieter Kleine to pull them out
(hans-dieter.kleine at medizin.uni-rostock.de).

With kind regards
Thomas Nebe



> ______________________________ Reply Separator
> _________________________________
> Subject: Definition of monoclonal
> Author:  dcdsflow at mint.net at INTERNET
> Date:    23/09/1998 19:43
> 
> 
> This a wqueation for the clinical Flow people,
> 
> It is well known that in in some NHL/B lymphomas and other LPD/B the
> B-cell
> population may express neither surface kappa or lambda light chains.
> Would
> you report this (in your institution) as a "monoclonal population" or as
> an
> "abnormal B-cell population" with neither kappa or lambda expression?
> My second question is if anybody has heard of a condition called
> "persistent
> polyclonal B-cell lymphocytosis"?  One of our pathologists recently
> mentioned this and wondered if this condition could be confused with a
> case
> which has a definite absolute lymphocytosis with absence of kappa and
> lambda.  I would think, polyclonal means having either kappa or lambda on
> the B-cells and therefore the absence of both light chains would not make
> the above mentioned condition part of a differential diagnosis.  Is this
> correct?
> 
> Thank you for you help
> Andrea Illingworth
> Dahl-Chase Diagnostic Services/Flow Cytometry
> 333 State Street
> Bangor, Maine 04401
> (207)990-4855
> 
> 
> 
> 



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