Lecture 3: ABO Blood Groups Part 2 Flashcards
ABO was the first ______ marker used in forensic and paternity testing.
genetic
If a discrepancy is detected and transfusion is necessary before resolution, only group ______ red blood cells shall be issued
O.
Define Discrepancy
Forward type and Reverse type do not match OR blood type does not match previous history
Example: What should you do?
Anti-A: 0
Anti-B: 0
A1 cell: 0
B cell: 4+
——> Later this is given
Anti-A,B: 2+
-Try typing with anti-A, B or
-Try cooling down the test system.
For the mean time, we will give O blood, because it is a subgroup
Interpretation: A sub
Explanation: Sub groups might have weak reactivity serologically on their red cells with typical reagents but may not recognize A as foreign.
2) Anti-A1 is not a naturally occurring antibody. It is immune stimulated, however it is shown here for example.
3) Infants, the elderly and the immunocompromised may not have the immune system capability to make enough antibodies that would be detected in their serum.
4) If blood type cannot be determined the safest possible products must be used for transfusion until the discrepancy can be resolved.
Example: What do I transfuse them?
Anti-A: 4+
Anti-B: 4+
A1 cell: 1+
B cell: 0
Later we are given A1 lectin: 0
-Try typing with A1 lectin
In this example, in the forward type, it looks like the patient shows antigens for both A and B. In the reverse type however it looks like we have a reaction that looks like an antibody against an A cell. So what do we do?
1) A1 lectin is a plant based lectin that is specific for those branchier chains of A antigen. When we test these cells for positive A1 antigen with A1 lectin, we’re looking for those branchy As. What we find here is a negative reaction with the A1 lectin.
2) So from this test we can call this patient/reaction a A2B or a A subgroup with regular B antigen.
3) What else we find is that antibody is weakly reactive, which is typical of an A1 specific antibody. So the antibody that this person made is going to be demonstated in our reverse type cells because they do have the branchy chains on them.
But if we tested this antibody against of those of an A2 person, that only have A antigen on the noncomplex chains, we probably would get negative reaction and we would be able to determine the specificity of that antibody created by that patient is directed towards the same thing that A lectin is directed against.
So we blood type this patient as again an A subgroup with B antigen, also expressed on the red cells. Now what do we transfuse this patient? We can transfuse them O blood, because we know that O blood does not have any antigens. We also can transfuse them B blood because they have the properly working B antigen as far as we know, because it has not made an antibody against any part of the B cell.
We should probably stay away from giving them A blood though. We could go through inventory and type any A1 blood that we want, with the A1 lectin, but it takes a lot of time, it’s not cost effective, about 20% of the blood is going to compatible, and when we already have blood on our shelf then type to be compatible, we will use that. So for this patient, I would say that we transfuse them with B blood or O blood.
Example: What the heck happened?
Anti-A: 4+
Anti-B: 0
A1 cell: 0
B cell:0
What should we do?
This patient looks like in the forward type, that they have A antigen expressed on their red cells and not B antigen. But in the reverse type they have made no antibodies. They don’t have any antibodies against A1 cell, nor the B cell, which we would expect.
So in this particular case, what happened is their immune system did not developed the expected immune response. And as we talked with antibodies, they are dependent on the patient’s ability to make antibodies. And this particular patient is not able to make antibodies, for whatever reason or not making enough antibodies that we can see them in the reverse type.
So they look like they would be able to tolerate a transfusion with A cells or B cells, because they don’t have antibodies against either one.
What this lack of antibodies indicates, for this patient is that they may have other immune responses lacking, and they may be called immunocompromised, which is that their immune system is not going to be able to make a response to defend itself against foreign pathogens. So that is really important for choosing special products for this particular patient.
As far for the serological testing, what we can do to try to resolve the discrepancy because there is a discrepancy. If we cannot call this patient an A blood type, until we have that expected result in the reverse type. We need to do is enhance this reactivity. And what we do to enhance the reactivity is again give the IgM antibodies their desired situation.
You can try to cool down the serological test to get a stronger reaction.
B cell cool: W+ —–> Interpretation: A
What the heck happened and what do I do?
Anti-A: 4+
Anti-B: 4+
A1 cell: 4+
B cell: 4+
Recognize first that there is too much reactivity and that we don’t want to enhance it.
Some of our options includes warm it (37C), do a saline control, or we can wash our cells.
By washing, we wash the patient cells (anti-A, anti-B) and we can warm the patient plasma (A1 cell and B cell) - Explore the forward type and the reverse type separately.
For forward type: A and B subgroups are _____ expressions of A or B _____ on the patient red cells.
weak, antigens
-There is no anti-A2 so when a person is negative with A1 lectin and positive with anti-A, we consider them a “subgroup”.
-A1 cells have normal A expression. They are positive for agglutination with A1 lectin and all anti-A reagents.
-A subgroups are negative with A1 lectin but probably positive with anti-A.
-There is no B1 lectin.
True or False: There is B1 lectin
False. There is no B1 lectin, but A1 lectin.
For reverse type: weak expression of ______ has more to do with a patient’s ________ system status than their subgroup status.
antibodies, immune
-Only consider the possibility of a subgroup if there is extra expression of antibody, not if antibody expression is missing.
-A2 cells are reagent cells that are known to have weak expression of A and type negative with A1 lectin. They are used to see if a patient’s extra antibody to A antigen reacts with all A cells or just A1 cells.
-There is no B equivalent.
Take a look at Typical extra workup tool slide if needed
What antigens does O Donor red cells present?
None, they don’t have end sugars, so they are a compatible donor for A, B, O, AB patients blood types.
What are the compatible red cell donors for blood type A, B, O, and AB?
A: A, O
B: B, O
O: O
AB: A, B, AB, O
For it will not react with patient antibodies
Plasma blood donor selection: which blood type is universal and why?
Remember that Plasma is based off of antibodies. AB does not have antibodies thus they are the universal plasma blood donor.
What are the compatible plasma blood donors for blood type A, B, O, and AB?
A: AB, A
B: AB, B
O: AB, A, B, O
AB: AB
Blood type O is a universal recipient for plasma blood.
85% of traumas, you can give A plasma to those patients
check powerpoint
What is the difference between naturally occurring antibodies vs immune stilumated antibodies?
-Naturally occurring antibodies are found in the plasma of individuals who have not been previously exposed to red cells through transfusion or pregnancy. Formed early in life and may persist.
-Usually IgM. Questionable clinical significance. May be non-specific or reactive to a variety of immune stimuli. Ex: anti-A, anti-B, anti-A, B, and anti-H
-Immune stimulated antibodies are made by individuals after exposure to red cells via transfusion or pregnancy. Formed later in life and may grow dormant or undetectable serologically.
-Usually IgG.
-Often indicates ability to have a reaction if exposed again. May be specific based on the type of antigen exposed.
Ex: anti-D, anti-Lea
what is “naturally occurring”
stimulated in the first 4 months of life from carbohydrate structures on gut bacteria and air particles.
“IgM” - for the most part though a significant portion of each type of antibody may form __ counterparts.
IgG
Most common is anti-A,B created by blood type O.
- Anti-A, B recognizes A and B antigens indiscriminately.
“Fix compliment”***
the clinical significance of this antibody is the size of IgM antibodies (cannot escape veins) and ability to fix complement (hemolyses everything)
“Cold reacting”**
room temperature detection serologically while also significantly reactive at body temperature
The strength (titer) of an antibody _____ in some disease states and old age.
decreases
