I know that my memory is poor, but I remember a long thread about this coming
up in regular intervals.
Indeed, there are possibilities of doublets, aggregates, coincident events,
receptor shedding... but as said below, there is also biology. From an
engineering point of view I would consider those cells interesting as they
should tell something about the traffic of those cells from a to b and thus
about the underlying regulation trying to keep numbers constant. Ideally I
would want to know about a and b as well.
Considering the comment below I actually wondered if those cells might have to
go for training elsewhere instead of being escapees or reexpress cd4. What's a
thymus of a HIV patient look like?
Gerhard Nebe-von-Caron
Research Scientist
Applied Science & Technology Group
SEAC - Safety and Environmental Assurance Centre
Unilever Research, Colworth Laboratory, Sharnbrook, UK - MK44 1LQ
Tel: +44 (0)1234 264822, Fax: +44 (0)1234 222552
E- mailto:Gerhard.Nebe-von-Caron@unilever.com
I actually picked here a contribution from my brother in 1997:
Wed, 10 Dec 1997 23:24:50 +0100
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
Next message: Jose C. Segovia: "RE: stage incubator"
Previous message: Mario Roederer: "Re: Permanent label for living cells?"
Dear collegues,
I got the impression that in this ongoing discussion two different phenomena
got
mixed up.
The one phenomenon that Maryalice described is the unspecific binding due to
substances in the blood sample that cause unspecific binding of some but not
all
antibodies in your panel. It disappears by washing before staining or by adding
access amounts of normal mouse serum. We see it in about one in a hundred cases
esp. in the BD CD3-FITC/CD19-PE and CD3-FITC/CD16&56 combination. You see only
two clusters in the two colour dot plot (see the quoted Cytometry paper).
The other phenomenon of CD4+8+ has first been described to my knowledge by
Diether Recktenwald in the application part of the first edition of the FACScan
manual (it was removed later on). There he used it as an example for a three
colour application where these double positive cells are propidium (or 7-AAD, I
donīt remember exactly) positive. I have seen a few patients, where in all
cases the normal mutual exclusive CD4 and CD8 are present and the third
cluster of double positives in addition (in our hands in the BD CD4-FITC/CD8-PE
test tube). The percentage of CD4+8+ was very stable in the two cases where we
were able to get consecutive tests over a longer period of time. Interestingly,
the first case was also a women from the lab where I did my PhD who was on
thyroid hormones for the same reason. Others were outside patients where we
could not get more clinical information. Taken all information together,
apoptotic escapees form the thymus would be an attractive explanation. As these
self reactive cells shouldnīt leave the special thymic environment, the
attribution to autoimmune diseases is not a bad idea.
I stop it here and apologize for my long comment I sent before.
Thomas Nebe
Klinikum Mannheim
-----Original Message-----
From: Maciej Simm [SMTP:simmmmer@yahoo.com]
Sent: Saturday, November 10, 2001 2:19 AM
To: Cytometry Mailing List
Subject: RE: RE: cd4 cd8 coexpression
Howard,
In my opition -
we look for CD4+ events in HIV patients to help us get an idea of the
state of the immune system of an HIV/AIDS patient(as one of many
assays). The virus attacks CD4+ cells, with preference for TH
lymphocytes (as opposed to DC's and monos etc etc), and as Mario
Roederer et al. showed using 11 color flow (if I remember right),
memory cells are more volnurable than naive cells.
According to my immunology textbook, double positive T cells are
undifferentiated T cells that have yet to undergo T cell receptor
rearrangement, so they're FAR from functional T lymphocytes that can
help in fighting the HI-virus.
Therefore, in my opinion, double positive T cells should not be
included in HIV patiens' T cell assessment.
In fact I would go as far as proposing that we look for remaining
MEMORY CD4+ T cells in HIV patients.
maciej
--- Howard.Gale@med.va.gov wrote:
>
> As I said in a previous message, the CD4+/CD8+ T-cells(CD3+)in our
> HIV+
> patients come in all varieties of brightness. The acquistion rate
> is in the
> 100-400 events/second range and I see no evidence of this being a
> doublet
> problem in the SSC vs CD45, CD3 vs CD4, or CD3 vs CD8 cytograms.
> These
> populations present consistently in patients over time and
> occasionally are
> a significant part of the CD+/CD3+ count. Is there any evidence
> that these
> dual positive cells (should not be counted as T-helper cells)and
> does the
> amount of relative fluorescence of CD4 and CD8 matter?
> -----Original Message-----
> From: Jacek Polski [mailto:jpolski@usouthal.edu]
> Sent: Thursday, November 08, 2001 10:33 AM
> To: cyto-inbox
> Subject: Re: RE: cd4 cd8 coexpression
>
>
>
> This may well be the answer to this intellectually stimulating
> issue, but
> the
> CD4+CD8+ events in my experience (usually below 1%) have the same
> intensity
> of CD8 as
> suppressor cells and slightly lower CD4 expression than helper
> cells. In my
> opinion,
> this observation supports the previously posted notion that CD4 can
> be
> expressed on
> activated CD8+ cells.
> Regards,
> Jacek Polski, MD
> Univ. South Alabama
>
>
> >>> <Alice.L.Givan@dartmouth.edu> 11/06 6:45 PM >>>
>
> Hello Flowers,
> I just wanted to re-inforce Ken Ault's comments about artifactual
> co-expression of CD4
> and CD8 due to coincidence of two cells in the laser beam. Two
> cells can
> coincide in
> the beam either because they are physically aggregated into a clump
> or
> because they
> just happen (by statistical probablility) to be suspended in the
> same
> volume of sample
> buffer as it moves past the laser.
>
> A coincidence artifact should be suspected if:
> 1) as Ken said, the frequency of these CD4/CD8 doubles decreases
> when the
> flow rate
> is decreased (although this may not happen if the cells are in
> actual
> clumps).
> 2) the intensity of each color on the double expressors is the
> same as the
> intensity of
> each color on the relevant single expressors. In other words, if
> the double
> expressors
> form the fourth corner of a perfect rectangle on a dot plot (with
> the negs,
> the PE+
> singles, and the FITC+ singles forming the other three corners),
> then you
> should
> be suspicious.
>
> Alice
>
>
> Alice L. Givan
> Englert Cell Analysis Laboratory
> of the Norris Cotton Cancer Center
> Dartmouth Medical School
> Lebanon, New Hampshire NH 03756
> tel 603-650-7661
> fax 603-650-6130
> givan@dartmouth.edu
>
__________________________________________________
Do You Yahoo!?
Find a job, post your resume.
http://careers.yahoo.com
This archive was generated by hypermail 2b29 : Sun Jan 05 2003 - 19:01:39 EST