Submitted by terrip_t1 t3_10at2kx in askscience
If I put a drop of blood under a microscope could experts be able to say what type it is? Is there a visible difference?
What does A,B, O etc actually mean?
And what does the positives and negative’s mean?
Thanks
Proportionally, how large are the antigens to the size of a blood cell?
Very tiny. A blood cell is around 7-8um across (there are 1000 um, micrometers or microns, in every millimeter). A surface protein is probably around the 10s of nm (nanometers, there are 1000 nm in every um) large. So roughly a thousand times smaller.
It is relatively easy to see cells with a microscope. With a light microscope you generally cannot see proteins because they are too small. Microscopes are limited by something called the diffraction limit, which is usually around 0.25um (or 250nm).
However you can see much smaller structures with an electron microscope and could presumably “see” surface proteins in that manner.
You could also use a stain or dye which colors the cell based on what surface proteins are present. You wouldn’t directly see the proteins, but you could differentiate blood type based on an indirect visualization (the color)
wait, the color of the entire cell would change based on the surface protein?
Depending on how you dye/stain the cell, yes. The surface proteins are distributed all across the surface. So if you use a dye which only sticks to those proteins it would color the whole surface of the cell.
There are ways of binding dyes to targeting moeties, like antibodies, that only stick to one type of target. So you could theoretically make different batches with different colors of dyes and bind them to different targeting moeties so only blood cells with that group get stained that color.
There are way, way, way easier and more practical ways to type blood though. So I don’t know that anyone would actually go through the work to do this or what it would accomplish. Just saying this is a way to achieve what the OP asked about and actually see a clear difference under the microscope.
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If you add a dye of a particular color that sticks to the particular surface protein, yes.
Thank you for explaining this so well
Would you be willing explain the other, rare blood types? For example a family member has the Kidd blood type) Found out the 8 blood types are just the most common, and there’s actually a bunch more.
Sure, but I’m not an expert by any stretch of the imagination. So the cell is surrounded by a membrane. That membrane is absolutely covered in tons and tons and tons of proteins which stick out above the surface of the membrane. We call these surface proteins because they extend above the surface. Those proteins can be used to mark what type of cell the cell is, interact with chemicals floating around outside the cell, bind the cell to various structural components or other cells etc. These are sometimes called surface antigens, because antibodies can be bind to them.
The normal blood group markers, the ABO system, represent a set of surface antigens. The ABO and Rh (that’s the +/- part) happen to be particularly important to how the body recognizes self vs foreign cells. So it’s really important to match those correctly.
But the blood cells have hundreds of different antigens. And just because the ABO and Rh groups are particularly important for recognition doesn’t mean those other antigens aren’t also used. And to make it even more complicated, different people seem to respond more or less strongly to different groups (although ABO seems to be close to universally important)
The only other one I know anything about is the Bombay Phenotype, which is when you have blood cells that have no antigens on them at all. Even O- has the base receptors that all blood cells have (H antigen) but if you have Bombay Phenotype then you don't have those either. Idk what medical issues this causes but it definitely makes it extremely hard if not impossible to get blood if you need it because you would have to get blood from someone else with that rare mutation: there is no other alternative.
Duff, Kelly and Kidd are the most clinically significant after AB0 and Rh. They are not generally reported in blood typing blood tests, instead a "screening" is performed. Here a general test of the presence of the most common antibodies in the patient's blood is done (so not the antigens on the blood cells).
In addition, you can do a "cross match" where donor blood is exposed to patient plasma to check for incompatibility
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Kidd antigens: A red cell has a ton of molecules on the cell surface that helps it do what a cell gotta do. One such molecule is an ion transporter (helps urea travel from one side of the cell membrane to the other. Almost all people have this protein, but at some point there was a mutation, so about 50% of people have “version a” while about 50% of people have “version b” and another 25% have both “Jka” and “Jkb”. These are the main Kidd antigens (Jka and Jkb are abbreviations). So, really there’s nothing special about having a Kidd antigen on your red cell. The problem happens if you’re missing one (ie type Jkb only) and get exposed to some blood from a Jka person. There’s a chance your immune system notices the difference and forms anti-Jka antibodies. Once the hospital knows you have formed this antibody, they’ll do their best to give you Jka-negative blood to prevent the transfusion from being destroyed by your immune system.
Just as an aside, there are tons of different blood group system (types of molecules on the red blood cell surface that can vary between one person and another). It’s impractical to “match” a blood unit up front to each persons molecules except for the ABO and Rh+/- everyone’s talked about. So we only special-select blood if there’s a known antibody, with the exception of sickle cell patients.
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Also interesting to note that the blood type O started out as 0 because those red blood cells had none of A or B.
Very interesting history of learning of blood types and early stages of trying transfusions.
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> > > > > The reason it's important to know this is because your body recognizes your cells by recognizing the cell surface antigens on your cells.
Well, mostly they don't recognize your own cells, they recognize anything foreign.
There are a few exceptions like NK cells recognizing MHC I from your own cells. But that's not involved here.
That is absolutely wrong. The immune system HAS to recognize self in order to attack the non-self. It does so mostly through two self-identification molecules (Human leukocyte antigens [HLA], and the major histocompatibility complex [MHC]). When the immune system doesn’t recognize the body’s own cells you get autoimmune diseases.
We're also talking about humoral immunity, which relies on antibodies. There is no self recognition involved there. As for cell-mediated immunity, it's true that the self MHC is part of what's required for recognition, but MHC alone is not sufficient - you need the foreign antigen loaded into the self MHC for recognition.
As for MHC and HLA, they are not two different molecules. MHCs are HLAs.
Thank you for this great explanation!
Great answer, I didn’t know this much about blood cells. Unfortunately your answer doesn’t answer OP’s question. What are the physical differences between these antigens?
Edit: apologies your answer answers partially. You explained what those letters and signs mean.
Well I mean the physical difference is the different antigens. That's about it.
Now I finally understand this, thank you.
One caveat: while Rh is a protein, A and B are carbohydrate antigens.
For the most part, you can’t tell under the microscope a person’s blood type. However, some antigens, if they’re missing entirely, result in misshapen cells. For example, if missing all Rh antigens (not just the D that gives +/- as mentioned above) you get a shape called “stomatocyte”, where instead of a pale round area in the middle, it looks more like a closed mouth.
Blood types can be visualized under a light microscope if IgM antibodies are added to the blood. This is a very fast and easy way to determine blood type. What you actually see is the blood cells clumping together (the actual A, B, and Rh proteins are far too small to be seen except perhaps by very specialized equipment).
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You can do this without a microscope as well, I've done this in uni somewhere in my first year. It's very easy and quick indeed.
The agglutination test at the bio labs for first year students don’t allow you to see individual cells. You simply see a reaction or lack thereof. That’s a bit different from what OP was asking.
>That’s a bit different from what OP was asking.
I'm aware, that's why it was a reply to the mention of that assay and not a direct post towards OP. I work with TM-proteins and do quite a lot of labeled Ab assays to indirectly prove something's there as it's just too small to see;)
The difference between the blood-types is the presence of certain antigens on the surface of the blood cell. These molecules are too small to be seen through a microscope. The "positive/negative" part is about another antigen on the surface of the cell, which is determined by another gene than the ABO system.
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Minute_Farmer t1_j471vtt wrote
There are 4 main types of blood: A, B, AB, and O. Any one of these 4 types can be + or -.
On the surface of the blood cell there are proteins called antigens. The important antigens for this explanation are: A antigen, B antigen, and Rh antigen.
Someone who has A antigens on their blood cells would be type A. Someone who has type B antigens on their blood cells would be type B. If you have both A and B, you're type AB. If you have neither A or B, you have type O.
Rh antigen decides if you're + or -. If you have the Rh antigen, you're +. If you don't, you're -.
So for example, someone with only B antigen and no others would be B-. Someone with A,B, and Rh antigen would be AB+.
The reason it's important to know this is because your body recognizes your cells by recognizing the cell surface antigens on your cells. If a foreign cell surface antigen is detected, your body will attack that cell. So for example, if you have A- blood, you can only recieve a blood donation of O- or A- blood. You can get O- because there's no antigens for your body to recognize as foreign (no B or Rh). In contrast, someone with AB+ blood can receive blood from any blood type, but someone with O- can only receive O-, despite being a universal donor (anyone can receive O- blood.)