BLOOD BANK

Welcome to the Clinical Laboratory

To learn about Blood Bank!

Why Study Blood Banking?

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Blood Bank is the area of the lab that prepares units of blood for patient transfusion.

Blood Bank also: Identifies and treats mothers and babies with

Hemolytic Disease of the Newborn (HDN). This is the condition which results from the mother being Rh negative and the baby being Rh positive.

Performs paternity testing

Many Different Blood Components are Given by the Blood Bank

All must be tested for multiple infectious diseases.All have expiration dates, because these are living

products.All have preservatives and anticoagulants.Given for different reasons:

To increase hemoglobin – Packed Red Cells To replace multiple coagulation deficiencies after

massive transfusions - Whole Blood and/or volume expanders

To increase platelet count – Separated Platelets

Blood Components Given by the Blood Bank

Whole Blood: Has RBC, WBC, Platelets, Plasma, & preservatives Approx. 500 ml (450 ml blood + 70 ml

anticoagulant/preservative) costs at least $550.Packed Red Cells: RBCs, and preservatives, to

replenish RBCs One unit is approximately 250 ml.

Fresh Frozen Plasma: Plasma & preservatives, To replenish coagulation factors such as

Factor VIII (hemophiliacs are deficient in Factor VIII and can bleed to death without treatment.)

Components Given by the Blood Bank

Washed or Irridiated Red Blood Cells: packed RBCs that have been washed irradiated. To decrease or eliminate the response of

the transfused T cells (lymphocytes). Given to the immuno-incompetent such as

chemotherapy patients.Platelets: To raise platelet count approx.

50,000-80,000 in cases where disease has eliminated platelets specifically.

Other unit types

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Autologous units From individuals who have donated a unit of

blood product for their own use only; typically used for generally healthy patients who have an elective surgery such as a total knee replacement.

 Directed units From individuals who have donated a unit of blood product for a specific person; should be type specific.

Work Done in Blood Bank Involves Knowledge of the Immune System

The immune system protects the body from potentially harmful substances by recognizing and responding to antigens. Antigens are molecules (usually proteins) on the surface of cells, viruses, fungi, or bacteria.

Nonliving substances such as chemicals, drugs, and foreign particles (such as a splinter) can also be antigens. The immune system recognizes and destroys substances that contain these antigens, generally by producing antibodies.

Antigens (Ag) That are Important in Blood Bank

Antigens - protein on a RBC surface which, when foreign to the person, can stimulate production of antibodies

Complex structure of: complex carbohydrates and/or proteins

Antigens (Ag) studied in blood bank are found on: red blood cells, white blood cells, platelets

Normally, a person does NOT produce an antibody to an antigen they own (this is very important!)

Simplified Mechanism of an Immune Response

First, recognition of the foreign substance (self vs foreign)

Second, destruction and removal of foreign substance. When antibodies attach to antigens, the resulting cell is targeted to be removed.

Third, repair of total system.

Antibodies (Ab)

Antibody (Ab) - protein that is produced in response to exposure to a foreign antigen; located in plasma/serum.

Function is to deactivate the antigenFirst there’s the antigen, then, if it’s foreign,

an antibody is produced by the immune system.

(There are some antibodies that are studied in Serology that are of interest because they are evidence of disease. Sometimes diagnoses are made solely on evidence of the antibody to the antigen that caused the disease. This is how Lyme Disease is diagnosed)

Immune System

Two basic mechanisms of immune system (again):To recognize foreign or abnormal substancesTo respond by enlisting various reactions to

eliminating that substance (immune response, generally involving antibodies)

Types of antibodies – these are different sizes and shapes, so have different purposes IgGIgMIgA Within blood bank (immunohematology) pregnancy and transfusion are the relevant sources of antibody stimulation.

Purpose of Immune System

To protect against pathogens and foreign substances (defense mechanism)

To identify malignant, aged/imperfect cells, and those infected by virus, bacteria, parasites, or cells coated with Ab.

To remove abnormal or damaged cells, like those above

Basically, to protect us.

Immune Response – why are antibodies produced?

Immunogenicity is the ability of an Antigen to stimulate the production of its corresponding Antibody in a person lacking that Antigen.

Some antigens have a stronger ability to stimulate antibodies than others . This is called immunogenicity.

Antibodies are very specific to the antigen.

Why Are These Reactions Even Studied in Blood Bank

These RBCs are circulating as they should. If we could see their antigens on the

surface, this might be what it would look like.

Antigen/Antibody Reaction

But when antibodies attach to the surface antigens,cells clump. Now imagine how that clumping affectscirculation.Both the clumping and the hemolysizing of cells kill the patient.

Antigen/Antibody Reaction

Clumped cells

Antigen-Antibody Reactions

In the previous slide, the immune system was stimulated and antibodies were produced.

What we try to do in Blood Bank is mimic the conditions of blood transfusion in the lab before the blood is given (in vitro), so that there is no immune response to the transfusion needed, thus, preventing an antigen-antibody reaction from occurring in the live patient (in vivo.)

Reactions are very rapid and often deadly, so work done in Blood Bank is very critical.

Blood Groups

Most people associate blood groups with what blood type someone is, for example O positive, A negative, B positive, etc... That assumption only accounts for two blood groups: ABO and Rh blood groups. There are many blood groups with various antigens associated with each.

We will only talk about A, B, O, AB, and Rh groups because they are the most common with the strong immunogenicity.

How Blood Groups Work

Type A people have A antigens on their RBC and B antibodies in their plasma

Type B people have B antigens on their RBC and A antibodies in their plasma.  Type O people have neither A nor B antigens on their cells but have both antibodies in their plasma.

Type O people have neither A or B antigens on their RBC , but they have A and B antibodies in their plasma.

Type AB people have both A and B antigens on their RBC, and no A or B antibodies in their plasma.

Another View of Antigen/Antibody Reaction

The reaction pulls the cells closer, causing clumping. Clumped cells do notcirculate well.

Crossmatching for Transfusions

Crossmatching the patient’s blood with a sample of the unit to be transfused is done in blood bank to be certain the transfusion will be compatible.

If the blood given is compatible the with patient, this is called a compatible transfusion and all is well. This means the patient hasn’t received blood with antibodies against any antigens present.

Crossmatching is very, very important and is always performed carefully and documented scrupulously.

Transfusions (cont.)

But if the patient receives a unit of blood with antibodies matching antigens present, the antibodies attach and begin destroying the cells (remember, the immune system gets rid of imperfect cells.)

This kind of transfusion is called an incompatible transfusion. If the antigen/antibody reaction involves group A, B, O, AB, destruction of the cells is immediate and often the patient dies quickly.

The Crossmatch

Again, all of this is tested for in the blood bank.

A very simple explanation of a crossmatch:adding antisera (the antibody) to the patient’s

cells where the antigens will be, if present. If there is an antigen/antibody reaction, the

cells clump (because the antibodies have attached to the antigens). The blue liquid

is the anti-A antisera.

See the clump?

clump?

The Crossmatch

This is what happens in an incompatible crossmatch:

Crossmatch (in vivo)

Compatible blood

Incompatible blood.See the clumping?

A Bit More About Blood Groups

At the beginning of the 20th century an Austrian scientist, Karl Landsteiner, noted that the RBCs of some individuals were agglutinated by the serum from other individuals. He made a note of the patterns of agglutination and showed that blood could be divided into groups. This marked the discovery of the first blood group system, ABO, and earned Landsteiner a Nobel Prize.

Karl Landsteiner and Alexander Wiener injected animals with Rhesus monkey cells to produce an antibody which reacted with 85% of human red cells, which they named anti-Rh.  Later, it became obvious that there were more antigens in the Rh monkey blood (see next slide!)

A blood group contains antigens controlled by a single gene. At the time of writing, there are 22 blood group systems, including the ABO, Rh, and Kell blood groups which contain antigens that can provoke the most severe transfusion reactions.

A Bit More About Blood Groups

ABO Blood Group: 4 antigens: A, B, AB, and A1

Rh Blood Group: 49 antigens, but D, C, E, c, and e are among the most significant.

But, when someone is said to be Rh positive, most of the time this means they have the D antigen.

Hemolytic Disease of the Newborn

HDN is a condition where the mother is Rh-, the father is Rh+ and the baby is Rh+.

The mother's immune response to the fetal D antigen causes antibodies to form against it. These antibodies are usually transported across the placenta and become part of the fetal circulation. This is when they attach to the baby’s D antigen.

Remember, some of these reactions cause destruction of the red cell (hemolysis). The baby can be in a life threating situation without treatment.

Treating HDN

The mother is most likely to be exposed to the baby’s blood the last three weeks of pregnancy. So that this type of reaction doesn’t happen, a pharmaceutical named RhoGam is given to the mother.RhoGam contains Anti-D, so if the mother does get the baby’s blood with its D-antigens, the RhoGam antibodies will attach, making the baby D-antigen unable to stimulate an antibody. To recap, the mother has anti-D that wants to attach to the baby’s D antigen should the two bloods mix.To keep this from happening, RhoGam, a manmade D antigen is given to the mom to bind her anti-D.

HDN blood cells

Review Questions

In Blood Bank, is only one product transfused to the patient? List as many as you can.

The concept of self and foreign material is important in immunology. What do these two terms, self and foreign mean?

True or false: ABO and Rh are the only two blood groups.

What is the process of confirming compatiblity units of blood for the patient called?

If the patient is A positive, they have A-antigens and what type of antibodies?

Review Questions

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When crossmatching, what does an incompatible unit look like?

What is the treatment preventing Hemolytic Disease of the Newborn called?