Erythrocyte antigens and the immune system Flashcards
What is the significance of understanding the interaction between antigens and antibodies in transfusion medicine?
Understanding the interaction between antigens and antibodies is crucial in transfusion medicine because it helps prevent immune reactions against transfused cells, ensuring recipient safety.
How are transfused exogenous cells treated by the recipient’s immune system?
Transfused exogenous cells are treated as ‘foreign’ by the recipient’s immune system, initiating an immune response similar to what occurs when targeting invading microorganisms.
What are antigens, and what can they stimulate?
Antigens are molecules present on the surface of infectious organisms, drugs, pollens, and cells. They can stimulate an immune response by binding to lymphocyte receptors. Alloantigens are those originating from the same species.
What determines the strength of the immune response to antigens, and why are highly antigenic antigens clinically significant?
he strength of the immune response to antigens depends on antigenicity, influenced by properties like complexity, biological activity, and size. Highly antigenic antigens are more clinically significant in red cell transfusions.
What happens when transfusions bypass innate responses and activate adaptive immune responses?
Transfusions bypass innate responses and activate adaptive immune responses, involving humoral (B lymphocytes producing antibodies) and cellular (T lymphocytes that destroy target cells) pathways.
What is complement activation, and how is it implicated in transfusion reactions?
Complement activation refers to a group of plasma proteins involved in immune responses. It is implicated in type II hypersensitivity reactions in transfusion recipients. There are four pathways for complement activation: classical, lectin, alternative, and terminal.
What are the four effects of complement activation, and how do they impact transfusion reactions?
The four effects of complement activation are cell lysis (target cell destruction), inflammation, opsonization (coating the target cell for phagocytosis), and interactions with other pathways. In transfusion, these effects can lead to recipient issues such as hemolysis and inflammation.
What is cellular immunity, and how does it function in the immune response?;
Cellular immunity is the immune response initiated by T lymphocytes to non-self antigens. T-lymphocytes differentiate into T helper cells (B-lymphocyte support) and T cytotoxic cells (directly destroy target cells).
What is the role of memory T-lymphocytes in the immune response?
Memory T-lymphocytes retain the memory of an antigen for future encounters, while other T-lymphocytes are involved in the immediate immune response.
How does T-lymphocyte differentiation allow the immune response to be more concentrated on specific aspects?
The differentiation of T-lymphocytes into T helper cells and T cytotoxic cells allows the immune response to be concentrated on either antibody production or the destruction of target cells, depending on the presented antigen.
What happens once a compatible T-lymphocyte is found in the immune response?
When a compatible T-lymphocyte is found, it requires three activating signals to initiate the immune response. Once fully activated, the T-lymphocyte transforms into a lymphoblast and secretes cytokines, which induce immune actions.
What are antibodies, and how are they produced?
Antibodies, or immunoglobulins, are a class of gamma globulins. They are produced and secreted by antigen-specific B lymphocytes, particularly B lymphoblasts, which are the activated form of the cell.
What are the stages of B lymphocyte activation upon recognizing a non-self antigen?
Activated B lymphocytes, or lymphoblasts, undergo three stages of activation upon recognizing a non-self antigen. Most activated B cells differentiate into plasma cells that synthesize and secrete specific antibodies, with some becoming memory B cells.
What is the primary immune response, and when does it become clinically significant?
The primary immune response is the body’s reaction to a new non-self antigen, with a natural lag phase. It is initially mediated by IgM but shifts to IgG after a few days, which is more clinically significant.
What is the secondary immune response, and how does it differ in dogs and cats?
The secondary response occurs in sensitized dogs or all cats transfused with incompatible blood. It is primarily mediated by memory B lymphocytes producing IgG antibodies and is considerably more potent and rapid.
Why is the secondary response more rapid and potent in cats, especially on their first transfusion?
The secondary response is more rapid and potent in cats on their first transfusion because they naturally have circulating antibodies to non-self red cell antigens. This response is mediated by memory B lymphocytes, even in the absence of prior exposure.
What does the term “Blood type” refer to?
Blood type refers to species-specific antigens present on the surface of erythrocytes.
Define “Blood group system” in the context of transfusion medicine.
A blood group system is one or more red cell antigens controlled by either a single gene or a cluster of two or more closely linked, homologous genes.
What does “Autosomal” refer to?
Autosomal refers to the characteristic being located on non-sex chromosomes.
Explain the term “Dominant” in the context of genetics.
Dominant refers to the relationship between two genes controlling the same characteristic, where the dominant gene is always expressed, masking the manifestation of recessive genes.
Define “Locus” in genetics.
Locus refers to the location of a gene controlling a particular characteristic, indicating a specific position on a chromosome.
What is an “Allele”?
An allele is a different version of a gene found at the same locus, resulting in variations in the expression of a characteristic.
What is a “Monoclonal” sample?
A monoclonal sample consists of identical antibodies recognizing an antigen at the same antigen-antibody binding site (epitopes), ensuring high specificity.
Define “Polyclonal.”
Polyclonal refers to a sample containing a mixture of antibodies capable of identifying the same antigen but at different antigen-antibody binding sites (epitopes).
Who discovered the ABO blood group system, and when?
Karl Landsteiner, an Austrian doctor, discovered the ABO blood group system in 1900.
How many blood groups are recognized in the DEA system for dogs?
Currently, seven blood groups in the DEA system are recognized: DEA 1, DEA 3, DEA 4, DEA 5, DEA 6, DEA 7, and DEA 8.
Are erythrocyte antigens genetically determined, and do they change over an individual’s lifetime?
Yes, erythrocyte antigens are genetically determined characteristics, similar to eye color, and they do not change over an individual’s lifetime.
What is the significance of the positive and negative designations in blood types?
If the gene controlling the expression of a particular antigen is present at the locus, that antigen will be expressed (positive), and if not present, the antigen will not be expressed (negative).
What are “natural antibodies,” and when are they present in dogs and cats?
Natural antibodies are present in dogs or cats without any antigen exposure. They are generated soon after birth or can be maternal antibodies passed from mother to offspring.
How does the prevalence of an antigen impact incompatibility reactions during transfusion?
An antigen with high prevalence causes fewer incompatibility reactions, as most individuals express the antigen, reducing the likelihood of antibody generation following a transfusion.
What are the two types of haemolytic transfusion reactions, and what influences them?
Acute haemolytic transfusion reactions occur during or within 24 hours of a transfusion, while delayed reactions can be primary or secondary immune responses, influenced by the antigenicity of the antigen.
What is unique about DEA 7 compared to other erythrocyte antigens?
DEA 7 is an unusual antigen as it is not part of the cell membrane but is soluble, manufactured by lymphocytes, secreted into plasma, and then absorbed onto the surface of RBCs.
