From lectures Flashcards
(37 cards)
Define antigen
A cell-surface protein capable of stimulating antibody production in an individual lacking that cell-surface protein
Define immunogen
the specific part, or parts, of an antigen that invoke the formation of antibody
define antibody
Immunoglobulin produced in response to the introduction of a foreign antigen stimulated by the immunogenic part of the antigen. The antibody produced may result in removal of that antigen
Why do IgM antibodies cause diresct agglutination while IgG require potentiators or AHG for agglutination.
IgM antibodies are large
difference between a direct and indirect test—-
what is an indirect antiglobulin test (IAT)? what is commonly used as a reagent and how?
testing antigen-antibody aggluttination to identify patient antibodies
mix patient sample with donor RBCs
incubated for binding
washing
describe fully an IAT
Primary - Incubation step
Secondary - Agglutination step
Explain the difference between an antigen and an immunogen
An antigen is any substance capable of inducing an immune response and can include non-immunogenic substances.
Immunogen specifically refers to the part of an antigen that can trigger the production of antibodies
What are antithetical antigens, and provide examples?
Antithetical antigens = antigens that are the result of alternative alleles at the same locus (different versions of the same antigen, determined by genetic variation).
Examples = M and N, S and s, and Fya and Fyb.
Describe the types of antibodies commonly found in blood groups and their characteristics.
Blood group antibodies are usually IgM or IgG, although some may be IgA.
IgM - naturally occurring,
IgG - immune.
what is the difference between IgM and IgG in terms of agglutination ability
IgM antibodies = directly agglutinate antigen-positive red cells in saline
IgG antibodies = most require potentiators or AHG to effect agglutination.
Why are ABO antibodies termed “naturally acquired”?
produced without requiring stimulation by foreign red cells
Most adults have antibodies to the A and/or B antigens naturally occurring to those ABO antigens they lack.
Discuss the factors influencing immunogenicity.
recognition of the substance as foreign
the molecular weight (typically at least 10,000 Daltons),
the composition of the substance (protein, carbohydrate, or lipid-based),
the amount and frequency of its introduction
define immunogenicity
ability to provoke an immune response
Explain why some IgG antibodies require potentiators or AHG for agglutination.
IgG is too small
AHG contains an antibody to IgG and so recognises and binds to the Fc portion of any IgG antibody.
Adding AHG allows cross-linking of red cells and therefore agglutination.
What factors contribute to the production of immune antibodies?
immunogenicity of the antigen concerned,
the amount and frequency of the stimulation involved,
the recipient’s immune response capability.
Why does red cell antibody production not routinely occur after transfusion or pregnancy????????????
What factors contribute to the production of immune antibodies?
Immunogenicity of the antigen: Some antigens are more likely to stimulate an immune response than others.
Amount and frequency of antigen exposure: Sufficient exposure to the antigen over time is required to trigger an immune response.
Recipient’s immune response capability: The recipient’s overall immune health and genetic factors influence their ability to generate antibodies.
Immunomodulatory factors: Certain medications, medical conditions, or immune-suppressing treatments may affect the immune response
Discuss the clinical significance of blood group antibodies.
medicine and prenatal care:
etermine compatibility between donor and recipient blood or tissues, preventing adverse reactions such as hemolytic transfusion reactions or hemolytic disease of the fetus and newborn (HDFN).
Blood group antibodies can cause agglutination or hemolysis of incompatible red blood cells, leading to serious health complications or even death if not properly managed.
What are the different ways blood group antigens can be introduced into circulation, and how do they lead to antibody formation?
transfusion of mismatched blood,
fetal-maternal blood exchange during pregnancy,
or transplantation of tissues containing foreign antigens.
When the recipient’s immune system encounters these foreign antigens, it may produce antibodies against them through the process of sensitisation, leading to antibody formation.
What percentage of transfused patients, pregnant women, and transplant patients are likely to produce red cell antibodies?????????????????
Transfused patients: Approximately 2-9% may produce antibodies after transfusion, depending on various factors.
Pregnant women: About 1% may develop antibodies due to fetal-maternal blood exchange.
Transplant patients: Less than 2% may produce antibodies after transplantation.
Explain the primary and secondary stages of agglutination in antigen-antibody reactions.
Primary stage: Occurs when antibody meets its corresponding antigen, leading to reversible binding via weak forces. This stage is also known as sensitisation.
Secondary stage: Involves cross-linking of red cells by antibody molecules, leading to visible agglutination. It depends on red cell dilution and attraction/repulsion forces.
How does AHG facilitate the agglutination of red cells coated with IgG antibodies?
AHG contains antibodies to IgG and recognizes and binds the Fc portion of IgG antibodies. This binding allows for cross-linking of red cells coated with IgG antibodies, facilitating agglutination.
Describe the blood group nomenclature system outlined in the lecture.
The blood group nomenclature system represents antigens, phenotypes, genes, and Rh haplotypes using various symbols and conventions, including capital letters, superscript/subscript letters and numbers, and positive/negative symbols enclosed in brackets.
