From: sbharris@ix.netcom.com (Steve Harris  sbharris@ROMAN9.netcom.com)
Newsgroups: sci.med
Subject: Re: Neutrophils vs. PMNs vs. Granulocytes
Date: 10 Oct 2003 20:12:53 -0700
Message-ID: <79cf0a8.0310101912.5c9d2a3f@posting.google.com>

moosor@lycos.com (Sergey Lupenko) wrote in message
news:<aaaa5256.0310101244.1d899b5c@posting.google.com>...
> Can anyone please clarify the nomenclature of these words?  Why are
> neutrophils sometimes referred to as Granulocytes or PMNs?  I thought
> a Granulocyte was a category including neutrophils, basophils, and
> eosinophils, yet I've heard Granulocyte in reference to only
> neutrophils, and then I've also heard neutrophils called
> hypersegmented PMNs.  I'm kind of confused.

It's bad form to refer use granulocyte as a synonyme for neutrophil,
since as you point out, basophils and eosinophils have granules, and
indeed are granulocyctes also. "Neutrophils" are merely neutrophilic
granulocytes, eosinophils are esosinophilic granulocytes (take up
red eosin), and so on. All neutrophils are granulocytes but not the
reverse.

PMN stands for polymorphonuclear leukocyte, which means literally the
white cell with the many-shaped nucleus. So it should ideally be
applied only to the hypersegmented (ie, mature) form of the
neutrophil. Alas, it isn't always, and has now been used as synonym
for neutrophil of any vintage so much that when you hear it, you can't
always be sure if hypersegmented or segmented neutrophil is meant, or
if all neutrophils are included. You can read about band-PMNs in the
literature, and if you believed in the term literally, this would be
an oxymoron, just as hypersegmented-PMN (which you also see) would be
a redundancy.

The best policy to avoid misunderstanding might be never to use the
term "PMN" at all, and to talk about only neutrophils (and subgroups
hypersegmented neutrophils, segmented neutrophils, band or stab
neutrophils, etc.) Alas, PMN is shorter to write in charts, and this
pretty much guarantees it a permanent place in charting in the future.

But not to worry. Technology has a fix for all this, and that is that
the valuble information that used to come from a hand differential has
gone down the rat hole anyway.  CBCs are now 99.9% automated and
untouched by human hands or eyes (just try getting any other kind in
the middle of the night for your febrile patient), and the machines
can only read dyes (to sort granulocyte classes) and can't tell
segmented neutrophils from any other kind of neutrophil. So generic
neutrophil counts are all you get anyway. So you can now call these
PMNs if you like.

SBH

From: sbharris@ix.netcom.com (Steve Harris  sbharris@ROMAN9.netcom.com)
Newsgroups: sci.med
Subject: Re: Neutrophils vs. PMNs vs. Granulocytes
Date: 10 Oct 2003 20:20:50 -0700
Message-ID: <79cf0a8.0310101920.7b87464b@posting.google.com>

moosor@lycos.com (Sergey Lupenko) wrote in message
news:<aaaa5256.0310101244.1d899b5c@posting.google.com>...
> Can anyone please clarify the nomenclature of these words?  Why are
> neutrophils sometimes referred to as Granulocytes or PMNs?  I thought
> a Granulocyte was a category including neutrophils, basophils, and
> eosinophils, yet I've heard Granulocyte in reference to only
> neutrophils, and then I've also heard neutrophils called
> hypersegmented PMNs.  I'm kind of confused.

I should add that as a neutrophil matures, it goes through a phase
where the nucleus is lumpy but not segmented yet. At that point it is
technically a PMN but not a segmented PMN. In practice, as I said, PMN
gets used as synonym for neutrophil. I think the idea is that this is
a cell whose nucleus has many shapes through TIME, even if it doesn't
have them right at this exact moment.

Hypersegmentation, BTW, is reserved for neutrophils with a lot of
extra lobes, and is classically associated with delayed cell division
and bone marrow release, as happens in severe B12 deficiency,
treatment with chemotherapeutic drugs that interfer with DNA
replication, etc.

SBH