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Band in Boston (Leukocytes #2)

Posted by Frederick Wasti
Nov 27 2013

[If you haven't yet seen my previous blog post, "And the Band Played On (Leukocytes #1)", please check it out first and then come back to this post, which is merely a continuation of it. Thanks.]

You might recall how my blood test results from 9/16 (from the Dana-Farber in Boston) looked, with their "odd" naming and counting of neutrophils -- well, here they are again, along with some more recent (and more "familiar" appearing) blood test results, as a comparison:

We saw, in my previous post, that the neutrophil count from 9/16, which (at first) seemed to be "missing", was indeed actually included, but that the neutrophils were (somehow) differentiated into Bands, Polys, and Metas. I still have to explain what Bands, Polys, and Metas represent, but first we have to go over how the five types of white cells are differentiated, and so that will be the subject of this post -- today you will see how we can visually tell the five leukocyte types apart.

[If you aren't familiar at all with the various types of blood cells, you might refer back to my post from 4/1/2012 on "Blood Cells 101".]

As mentioned in the last post, the five white cell types fall into two groups, "granulocytes" and "agranulocytes", the distinction being based upon whether the cells show specks or granules in the cytoplasm (i.e., the material within the cell that is outside the nucleus). Let's look at the granulocytes first:

If you look carefully at the above granulocyte drawings, you should notice visible reddish granules in the eosinophil and even more obvious bluish (or purplish) granules in the basophil, and perhaps, if you look really carefully, some faint, small reddish or pinkish granules in the neutrophil. (In contrast, the agranulocytes - lymphocytes and monocytes - do not show such granules in their cytoplasm.)

An erythrocyte (i.e., a red blood cell) is included in the above image to allow for estimating the size of the white cells. Since, when a blood smear is examined microscopically, the very numerous red cells will appear in every field of view, and since nearly all red cells are approximately the same size as each other, each red cell makes a useful "yardstick" for judging the relative sizes of white cells. You may have noticed above that the three granulocyte types are each somewhat larger than are red cells.

[This size estimation ability may not seem to be all that useful just yet, when looking at just the granulocytes, because each granulocyte is roughly the same size as every other granulocyte, but size estimation will seem to be more useful when we get to the agranulocytes, since lymphocytes are distinctly smaller than the granulocytes, while monocytes are often larger.]

Let's take a look specifically at the neutrophils first:

In the above microscopic image, there are four neutrophils. Note that they are distinctly larger than are the red cells, that their cytoplasm is "speckled" (i.e., granulated) (although not obviously so), and that their nuclei are multilobed (usually consisting of from two to five lobes, connected by thin filaments, not usually visible at this magnification). (You can also see that the more numerous red cells lack nuclei, and you should also be able to spot about a dozen or so very small platelets as well.)

Taking a closer look at another neutrophil, ...

... the small, faint, pinkish granules are (slightly) clearer, and the nuclear filaments can also be seen as well.

Of course, you already know that all these ~stained~ white cells no longer look white after staining, and it is, in fact, the nature of neutrophils and the stain that colors their granules that is the reason for their name. Blood stains generally are made of a mixture of several stains of varying pH values, and it is the ~neutral~ stain, and not the acidic or alkaline stains, that end up coloring their granules -- hence, they are called "neutro-phils" because they have an affinity for (or "love") the neutral stain in a blood stain mixture (the "phil" comes from the Greek word "philein", meaning "to love").

So, what do you have to remember about neutrophils, in order to be able to recognize them? Well, it really boils down to just three characteristics:

1. Neutrophils show faint reddish or pinkish granules in their cytoplasm.

2. Neutrophils show a multilobed nucleus (of two to five lobes). (In fact, if you spot a white cell with more than two lobes to its nucleus, it is likely to be a neutrophil.)

3. Neutrophils are "somewhat" larger (perhaps very roughly 1.5 to 2 times greater in diameter) than red cells, and are roughly the same size as eosinophils and basophils.

OK, let's take a look at eosinophils ("ee-oh-sin-oh-fills") next. Eosinophils are granulocytes that have (when stained) large reddish granules in their cytoplasm. Compared to the neutrophils, the granulation is much more obvious. Most of the time the nucleus in an eosinophil is bilobed (i.e., having two lobes) in appearance. Take a look at the following image, of two eosinophils and a neutrophil, to see how these two types of granulocytes compare in size, in granulation, and in nucleation:

By now, you're probably trying to figure out the etymology of the name "eosinophil". You already know that the "-phil" means "loving" -- it's just the "eosino-" part of the name that might be confusing -- it turns out that the granules of eosinophils have an affinity for a particular ~acidic~ stain with the name of ~Eosin~. [Eosinophils could also, because of this, be referred to as "acidophils" (and sometimes they are), but that's a considerably less common name for these particular white cells, for some inconsistent reason as of yet unbeknownst to me.]

Anyway, what do you have to remember about eosinophils, in order to be able to recognize them? Well, once again, there are just three characteristics to look for:

1. Eosinophils show fairly obvious reddish granules in their cytoplasm (redder and more distinct than the pinker and much smaller granules in neutrophils).

2. Eosinophils usually show a bilobed nucleus.

3. Eosinophils are "somewhat" larger (perhaps very roughly 1.5 to 2 times greater in diameter) than red cells, and are roughly the same size as neutrophils and basophils.

So, then we have the third type of granulocyte, the basophil, to consider:

Basophils are somewhat like eosinophils, except that the granules are more purplish or bluish, rather than more reddish, as in eosinophils. Sometimes this difference may not be overly obvious, though, since the reddish granule color of eosinophils can sometimes seem a bit on the purplish side, while the bluish granule color of basophils can also tend toward purplish. However, sometimes the basophils can also be seen to have granules that are somewhat larger in size, or "coarser" in appearance, than those seen in eosinophils.

In the image above, the two basophils seem not too similar in appearance. Part of this is because the granules do differ in color somewhat between the two cells, but part of the difference is also because the nucleus is closer to the viewer in the upper cell, while the nucleus is farther from the viewer in the lower cell, so that, in the upper cell, the nucleus is hiding many of the granules behind it, while, in the bottom cell, the granules are doing a good job at hiding the nucleus behind them.

Basophils get their name because they and up reacting to the ~basic~ (or alkaline) stain in a typical blood stain mixture.

OK, so what do you have to remember about basophils, in order to be able to recognize them? Well, once again, there are just three characteristics to look for:

1. Basophils usually show obvious bluish or purplish granules in their cytoplasm (sometimes appearing a bit more pronounced than the granules of eosinophils, but always ~much~ more obvious than the faint granules of neutrophils).

2. Basophils usually show a bilobed or U-shaped nucleus.

3. Basophils are "somewhat" larger (perhaps very roughly 1.5 to 2 times greater in diameter) than red cells, and are roughly the same size as neutrophils and eosinophils.

Let's now turn our attention to the agranulocytes (a.k.a., the non-granulocytes), which include the lymphocytes and monocytes:

First, it should be clear (so to speak) that, as the name suggests, there are ~no~ granules in the cytoplasm of the ~non~-granulocytes (i.e., the agranulocytes). Second, it is apparent that there are size differences to be considered with the agranulocytes. And, finally, it should be noted that agranulocytes have a relatively simple nucleus, generally U-shaped or even cup-shaped in appearance.

Taking a look at lymphocytes first, ...

... it can be seen that lymphocytes are quite a bit smaller than any of the other white cells, with a size generally roughly the same as that of the red cells (or a bit larger). There is not too much cytoplasm to look at, because the nucleus of a lymphocyte, approximately round or oval in shape, seems to fill up most of the inside of the cell -- however, there are still no granules to be seen in the limited amount of cytoplasm that is visible.

So, to most easily distinguish a lymphocyte, look for these three characteristics:

1. Lymphocytes do not show much cytoplasm, but what cytoplasm they do show is relatively clear, with no obvious granules.

2. Lymphocytes show a round or oval nucleus that seems to almost fills the cell.

3. Lymphocytes are easily the smallest of the white cells, being very close to the red cells in size.

In contrast, monocytes, ...

... the other type of agranulocytes, are generally the largest of all the white cells, with a diameter of often approximately twice that of red blood cells. [The Golgi apparatus shown in the above monocytes, which is involved with cell secretion, is not usually too visible in most blood smear preparations.]

The nucleus of a monocyte is quite large (although it does not come close to filling up such a large cell) and is usually U-shaped or cup-shaped in appearance, although sometimes it can be irregular (even "blobby") in shape.

There are no granules in a monocyte's cytoplasm -- although the cytoplasm may not be totally transparent, ...

... there still is a lack of any colored granules to be seen in it.

Therefore, the three main characteristics to look for in trying to distinguish a monocyte are:

1. Monocytes, being agranulocytes, lack any visible colored granules in their cytoplasm.

2. Monocytes show a large nucleus that is U-shaped, cup-shaped, or irregular in shape.

3. Monocytes are significantly larger than any other white cells, often having a diameter twice (or even more than twice) that of the red blood cell "yardsticks".

Now, please do not be intimidated by all these characteristics. First, I have tried to limit the similarities and differences to just three characteristics for each of the five types of white cells -- you really have to look for only the granulation (if any) in the cytoplasm, the shape of the nucleus, and the relative size of the cell. It's that "simple". Really. Besides, you really don't have to be "good" at distinguishing these cell types -- I am merely trying to ~acquaint~ you with the morphology of the types of leukocytes. So, no pressure, right?

Well, er, um, maybe just a wee bit of pressure: (<grin>) How about a little quiz, where you can prove (to ~yourself~) that you can indeed do a pretty good job at telling one white cell type from another? You can grade it yourself, and you can score it on a "pass-pass" basis. And it's an "open book" quiz (or an "open blog" quiz anyway - you can look at all the characteristics provided above. So, just how hard can it be, right? Eh?

Just to help you succeed more easily, I'll even summarize the most useful things to look for before we begin, OK?

1. If the nucleus shows three or more lobes, it's likely to be a neutrophil.

2. If the cytoplasm shows obvious reddish granules, it's likely to be an eosinophil.

3. If the cytoplasm shows obvious bluish granules, it's likely to be a basophil.

4. If the cell is a very small cell, similar to a red cell in size, it's likely to be a lymphocyte.

5. If the nucleus seems to fill up most of the cell, leaving room for very little cytoplasm, it's likely to be a lymphocyte.

6. If the cell is a very large cell, at least twice as wide as a red cell, it's likely to be a monocyte.

Finally, I'll provide one more hint for the quiz: I'm going to show five images, and they are for the five types of white cells, one image for each type. Therefore, you might be able to come up with the answer for a "tougher" image by "the process of elimination". OK? (The bad news is that, if you guess one incorrectly, and are using "the process of elimination", you probably have at least two of 'em wrong - <grin>.) Of course, "in the real world", in a blood lab, the technicians can't use "the process of elimination" when counting cells.

So, grab a scrap of paper (perhaps the back of an envelope from a bill that you weren't going to pay anyhow, say), number it from 1 to 5, and try to put an 'N', an 'E', a 'B', a 'L', or an 'M' for each cell type next to each number. (See? -- you don't even have to spell out the names -- easy, eh?)

Ready? Here goes -- here are your "unknown" white cell types:

I'll provide the answers in the next blog entry -- so, please stay tuned. (And don't lose your "scrap of paper".)

[Please note: I did intend to include a little information on the background for the expression "Banned in Boston" as part of this entry, but, in order to get this blog entry "out the door", I will delay writing that until probably sometime after posting the third issue of this series (which will include the answers to today's little quiz), entitled "Band of Blood-ers (Leukocytes #3)" - as I said very recently, "please stay tuned".]

Categories: General, Leukemia