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 |