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Probably worth mentioning the new research that the spleen serves as a reservoir for monocytes. 220.127.116.11 (talk) 20:56, 6 August 2009 (UTC)
A labeled version of that electron microscope image would rock. One with arrows and call-outs. I can't identify anything but red and white cells in that picture. TomCerul (talk) 19:00, 9 November 2009 (UTC)
The word unilobar was added in the first edit of 22 January 2014, making the sentence in the lead read as Monocytes have bean-shaped nuclei that are unilobar, which makes them one of the types of mononuclear leukocytes (agranulocytes). But the accompanying image very clearly shows two illustrative monocyte cells with nuclei that are each multilobar. So which description is correct? Milkunderwood (talk) 02:43, 27 June 2015 (UTC)
Hi. Good question, and it's one that Wikipedia ought to be clearer about, for the sake of all of us who aren't biologists or pathologists (in other words, most humans and most Wikipedia readers). We should be able to come here to Wikipedia and sort out the 101-level concepts of this business (mononuclear, multinuclear, and polymorphonuclear). Back in 2014, digging around in Dorland's and elsewhere, I found that the distinction of lobes of the nucleus lies at a rather high threshold, higher than the one most readers would expect (and which is reflected in your question). The threshold is at the level of being so thoroughly furcated that the portions look, or almost look, as if they were separate nuclei (in which case they are considered lobes). For example, the image currently at the top of the polymorphonuclear leukocyte article (File:pBEosinophil.jpg) shows this heavy degree of furcation. In contrast, in the image at the top of this article (File:Monocytes, a type of white blood cell (Giemsa stained).jpg), one can clearly see that each cell has only one nucleus, and the waviness of the nuclear membrane doesn't extend to the heavy furcation that would qualify the portions as lobes, in the way that pathologists would count lobes.
So the above is basically the answer to the posted question. I also wanted to post here some info that should eventually be incorporated into Wikipedia's various cell- and nucleus-related articles, when we get time for such development. It is as follows:
There are a few discrepancies between the literal meanings of the strings of combining forms and the modern usage of the words. They mostly align, but with some fudge factor. We can see that mono- + -nuclear, "one nucleus", corresponds to any cell with a single nucleus, as opposed to multinucleated cells (multi- + -nuclear, "multiple nuclei"). Now, let's consider the word monocyte (mono- + -cyte, "one cell"). If we are even going to use roots meaning "one cell" when we really mean "one-nucleus cell"—well, OK, let's accept that on the principle of shorthand. But even so, if life were fair, then monocyte really ought to be synonymous with mononuclear cell, in any sense or context. But wouldn't you know, in modern usage, it's not. There are trillions of mononuclear cells in the human body (single-nucleus cells), but only a mononuclear class of leukocytes gets called by the name monocyte (there's the first bit of oddness)—and further more, even the polymorphonuclear leukocytes (poly- + morpho- + -nuclear, "multiple forms of nucleus") are in fact mononuclear cells—not multinucleated ones, although the lobes make them look, or almost look, that way—so contradistinguishing one class of leukocytes from another by calling them monocytes (a second bit of oddness) is a bit silly, if one were interested in controlling the language. But alas, one is not—or I should say, most people aren't, and thus we humans usually don't do it. Which makes for all kinds of belabored pedagogy when we try to learn. It's a sad little endemic pathology. At any rate, one can see behind today's usage oddnesses a hint of an earlier era when the state of the art in the magnification and resolution of microscopy was still often having trouble differentiating cells with deeply furcated nuclei (i.e., lobed nuclei) from those with multiple nuclei. Quercus solaris (talk) 14:22, 27 June 2015 (UTC)