Blood transfusions and the immune system - Blood Groups and Red Cell Antigens - NCBI Bookshelf
To understand blood typing, it is necessary to define antigen and antibody. An antigen is a RELATIONSHIPS BETWEEN BLOOD TYPES AND ANTIBODIES. With it, blood transfusions must be performed with great care. case of a foreign red blood cell antigen, the patient's pre-existing antibodies bind to the antigen. Differences Between Antigen and Antibody. Antibodies, also called immunoglobulins, Y-shaped molecules are proteins manufactured by the.
Aside from the sugar glycan or carbohydrate antigens, the red blood cell membrane contains three types of protein that carry blood group antigens: Click on the blood groups to find out more about the antigens that define it.
Red blood cell antigens determine your blood group The antigens expressed on the red blood cell determine an individual's blood group. The functions of many of the blood group antigens are not known, and if they are missing from the red blood cell membrane, there is no ill effect.
This suggests that if the blood group antigens used to have a function, e. But the presence or absence of red blood cell antigens becomes extremely important when blood from different people mixes, e. This also happens when a mother becomes pregnant because during labor, a small amount of fetal blood enters her circulation.
Antigen vs Antibody – What Are the Differences? | Technology Networks
In these circumstances, exposure to the foreign antigens on the red blood cells can trigger immune reactions. It is not possible to completely remove the danger of adverse reactions when blood from two people mix, but the danger can be minimized. Before a blood transfusion takes place, the blood to be donated must be "typed and cross matched" with the patient's blood to ensure immune compatibility see Chapter 3.
In pregnancy, the risk of the mother's immune system attacking the foreign antigens present on her fetus' red blood cells is prevented by giving the mother antibodies to cover fetal red blood cell antigens and removing them from the mother's circulation before her immune cells find them see Chapter 4.
It is determined by the frequency of the three alleles of the ABO gene in different populations. Blood type O is the most common worldwide, followed by group A. Group B is less common, and group AB is the least common. The frequencies of ABO and Rh type in the United States were recently examined by collecting data from blood donors over a 10 year period 1. The charts below summarize the findings for blood type and race: The highest percentage of RhD- was found in white donors It is also the most common blood type in populations around the world, including the USA 1 and Western Europe 2, 3.
Therefore, the main symptoms of this type of reaction are fever and chills. Delayed hemolytic transfusion reaction Delayed hemolytic transfusion reactions may occur as soon as 1 day or as late as 14 days after a blood transfusion.
The donor RBCs are destroyed by the recipient's antibodies, but the hemolysis is "delayed" because the antibodies are only present in low amounts initially.
Differences Between Antigen and Antibody
The recipient's antibodies were formed during a previous sensitization primary stimulation with a particular antigen. However, by the time a cross match is done, the level of antibody in the recipient's plasma is too low to cause agglutination, making this type of reaction difficult to prevent. Likewise, during the blood transfusion the level of antibody is too low to cause an acute transfusion reaction. However, during the blood transfusion, as the patient re-encounters the antigen, his or her immune system is stimulated to rapidly produce more antibodies secondary stimulation.
Over the following days, the recipient's antibodies bind to the donor RBCs, which are subsequently removed from the circulation by macrophages extravascular hemolysis. The clinical outcome depends upon the rate at which the patient can produce antibodies and hence destroy the donor RBCs.
Usually, this type of reaction is much less severe than acute hemolytic reactions. This type of transfusion reaction is associated with antibodies that target the Kidd and Rh antigens.
White blood cell incompatibility The most common transfusion reaction is a fever without signs of hemolysis. Only when other potentially severe causes of transfusion reactions have been excluded may FNHRT be diagnosed. The cause is thought to be the patient's preformed antibodies attacking transfused WBCs, binding to their HLA antigens. Another factor might be that during the storage of blood units, WBCs release cytokines that may provoke a fever when the unit of blood is transfused into a patient.
In addition, patients who receive multiple transfusions may be given an anti-pyretic before the transfusion to lessen fever symptoms.
Differences Between Antigen and Antibody
Post transfusion purpura PTP: Platelet incompatibility Post transfusion purpura PTP is defined as a thrombocytopenia low number of platelets that occurs 5 to 10 days after a platelet transfusion. Patients are at risk of bleeding, and bleeding into the skin causes a purplish discoloration of the skin known as purpura.
PTP is caused by the recipient having a platelet-specific antibody that reacts with the donor platelets. The recipient's own platelets are also attacked. The platelet antigen HPA-1a appears to be most frequently targeted.
PTP is more common in women because pregnancy increases the likelihood of forming the platelet-specific antibody. It may also have formed after an earlier platelet transfusion. Treatment includes the use of intravenous immunoglobulin to neutralize the antibodies or to remove them from the plasma by plasmapheresis.
IgE anti-allergen antibodies Some patients can have an allergic reaction after their blood transfusions—they report feeling itchy and break out into hives urticaria.
Antibody and antigen
This is more common in patients who have a history of allergic conditions such as hay fever. This type of allergic reaction happens when existing IgE antibody binds to its antigen and triggers the release of histamine from the patient's mast cells and basophils.
- Antibody-antigen complex
- Blood Type - Antigens And Antibodies
In an allergic reaction to a blood transfusion, either the transfused blood contains IgE that binds to antigen from the recipient's blood, or the antibody is the recipient's own and binds to antigen in the transfused blood. Fortunately, symptoms are usually mild and can be controlled by stopping the transfusion and giving antihistamines. IgA anti-plasma protein antibodies Anaphylaxis is a life-threatening allergic reaction that can occur after only a few milliliters of blood have been transfused.
The patient reports difficulty breathing and may be wheezing and coughing. There may also be nausea and vomiting in the absence of a fever. Other signs include low blood pressure, loss of consciousness, respiratory arrest, and circulatory shock. Urgent treatment is essential and includes giving epinephrine. Usually the antigen that triggers the anaphylaxis is not known. In the case of patients with IgA deficiency, it is thought that the presence of IgA in the donor's plasma is the trigger.
IgA-deficient patients have a mild immunodeficiency that may not have been diagnosed. Because they lack IgA, their immune systems can be sensitized to it.
Although this type of transfusion reaction is rare in these patients, special precautions are taken to reduce their risk of exposure to IgA in blood products. Donor anti-leukocyte antibodies attack Transfusion associated lung injury TRALI is a rare and occasionally fatal transfusion reaction characterized by a sudden onset of shortness of breath.
The underlying mechanism is not fully understood, but it is thought to involve the transfusion of donor plasma that contains antibodies that attack the recipient's WBCs. These donor antibodies bind to, and cause the aggregation of, the recipient's WBCs in the blood vessels that supply the lungs.
The white cells release inflammatory mediators that increase the permeability of the lung capillaries, causing fluid to accumulate in the tissue of the lungs, a condition known as pulmonary edema for which supportive treatment is given. Donor T cells attack Transfusion associated graft-versus-host disease TA-GVHD arises when transfused blood cells the graft attack the patient's own cells the host.
It is more common in immunocompromised patients whose immune systems fail to eliminate the transfused cells.
Instead, the surviving donor T cells attack cells that bear HLA antigens. This type of reaction becomes apparent about one week after the transfusion.
Glycoproteinswhich traverse the red cell membrane, have a polypeptide backbone to which carbohydrates are attached. Another integral membrane glycoprotein, glycophorin Acontains large numbers of sialic acid molecules and MN blood group structures; another, glycophorin Bcontains Ss and U antigens.
The genes responsible for inheritance of ABH and Lewis antigens are glycosyltransferases a group of enzymes that catalyze the addition of specific sugar residues to the core precursor substance. For example, the H gene codes for the production of a specific glycosyltransferase that adds l-fucose to a core precursor substance, resulting in the H antigen; the Le gene codes for the production of a specific glycosyltransferase that adds l-fucose to the same core precursor substance, but in a different place, forming the Lewis antigen; the A gene adds N-acetyl-d-galactosamine H must be presentforming the A antigen; and the B gene adds d-galactose H must be presentforming the B antigen.
The P system is analogous to the ABH and Lewis blood groups in the sense that the P antigens are built by the addition of sugars to precursor globoside and paragloboside glycolipids, and the genes responsible for these antigens must produce glycosyltransferase enzymes. The genes that code for MNSs glycoproteins change two amino acids in the sequence of the glycoprotein to account for different antigen specificities.
Additional analysis of red cell membrane glycoproteins has shown that in some cases the absence of blood group antigens is associated with an absence of minor membrane glycoproteins that are present normally in antigen-positive persons.
Methods of blood grouping Identification of blood groups The basic technique in identification of the antigens and antibodies of blood groups is the agglutination test. Agglutination of red cells results from antibody cross-linkages established when different specific combining sites of one antibody react with antigen on two different red cells.
By mixing red cells antigen and serum antibodyeither the type of antigen or the type of antibody can be determined depending on whether a cell of known antigen composition or a serum with known antibody specificity is used. In its simplest form, a volume of serum containing antibody is added to a thin suspension 2—5 percent of red cells suspended in physiological saline solution in a small tube with a narrow diameter.
After incubation at the appropriate temperature, the red cells will have settled to the bottom of the tube. These sedimented red cells are examined macroscopically with the naked eye for agglutination, or they may be spread on a slide and viewed through a low-power microscope.
An antibody that agglutinates red cells when they are suspended in saline solution is called a complete antibody.