exam review

What are antigens/immunogens?

Substances that react with antibodies; may or may not trigger an immune response.

What is immunogenicity?

The ability of an antigen to trigger an immune response leading to antibody formation.

What is an immunoglobulin?

A protein produced by plasma cells from B-lymphocytes; includes 5 classes: IgG, IgA, IgM, IgD, IgE.

What is isotype/class switching?

The process where activated B-cells change antibody class (e.g., IgM to IgG) without changing antigen specificity.

What are isoagglutinins?

Naturally occurring ABO antibodies, usually of IgM class.

What are naturally occurring antibodies?

Antibodies present without known exposure, produced due to cross-reactivity with bacterial or food antigens.

What are immune antibodies (alloantibodies)?

Antibodies formed after exposure to antigens, typically IgG, that react at 37°C and are clinically significant.

What are autoantibodies?

Antibodies directed against self RBC antigens, often causing panagglutination.

What is panagglutination?

Condition where patient serum agglutinates all reagent RBCs.

What is chimerism?

The presence of two RBC populations in one person, either true (twins) or artificial (transfusion/transplant).

What did Landsteiner discover about the ABO blood group system?

He observed RBC agglutination when mixing blood from different individuals.

What are ABO antigens?

Carbohydrate structures located on the RBC membrane.

What are ABO antibodies?

Mostly IgM antibodies that are naturally occurring.

What is forward typing in blood typing?

The process of mixing patient RBCs with anti-A/anti-B antisera to detect antigens.

What is reverse typing in blood typing?

The process of mixing patient plasma with A1/B reagent cells to detect antibodies.

Why are ABO IgM antibodies clinically significant?

They efficiently activate complement, leading to rapid intravascular hemolysis.

What is Landsteiner’s Rule?

States that if an antigen is present, the corresponding antibody is absent, and vice versa.

What is the mechanism of transfusion reactions?

Recipient antibodies bind to donor RBC antigens, resulting in agglutination and hemolysis.

What characterizes an acute hemolytic transfusion reaction (AHTR)?

Symptoms include fever, chills, hypotension, hemoglobinuria, renal failure, and shock.

What is the universal donor blood type?

O-negative RBCs.

What is the universal recipient blood type?

AB-positive RBCs.

What is the ideal plasma donor blood type?

AB type plasma.

What is the ideal plasma recipient blood type?

O type plasma.

What is the purpose of an antibody screen (IAT)?

To detect unexpected, clinically significant antibodies (usually IgG).

What is the first step in the antibody screen (IAT) method?

Mix patient plasma with group O screening cells.

What is the purpose of incubating at 37°C in the antibody screen (IAT)?

To allow binding of antibodies to corresponding antigens on screening cells.

What is added after washing unbound antibody in the IAT method?

Anti-IgG (AHG) is added.

What does agglutination indicate in the IAT method?

Agglutination indicates a positive test, meaning unexpected antibodies are present.

What does the antibody screen NOT detect?

It does not detect cold IgM antibodies.

What are general rules for ABO discrepancies?

Suspect the weakest reaction, repeat testing, check patient age, diagnosis, and transfusion history.

What is Category I of ABO discrepancies?

Unexpected reverse reactions caused by weak or missing antibodies.

Who commonly shows weak or missing antibodies?

Newborns, the elderly, immunodeficient individuals, those with leukemia/lymphoma.

What is the resolution for Category I discrepancies?

Incubate reverse at room temperature and then at 4°C with controls.

What is Category II of ABO discrepancies?

Weak or missing RBC antigens caused by A/B subgroups or diseases.

What are some causes of Category II discrepancies?

Acquired B phenomenon, leukemia, Hodgkin’s disease, BGSS.

What is the resolution for Category II discrepancies?

Extend incubation, test at 4°C, and enzyme-treat RBCs.

What is Category III of ABO discrepancies?

Plasma/protein abnormalities in antibody screening.

What causes Category III discrepancies?

Rouleaux formation, high fibrinogen levels, dextran interference.

What is the resolution for Category III discrepancies?

Saline replacement and thorough washing of cells.

What is Category IV of ABO discrepancies?

Miscellaneous causes of unexpected reactions.

What might cause Category IV discrepancies?

Cold autoantibodies, unexpected alloantibodies, mixed populations.

What is the resolution for Category IV discrepancies?

Use of a pre-warm technique and antibody identification.

What is immunity?

Resistance to infection.

How is infection different from disease?

Infection is an invasion, while disease is altered health due to infection.

What is normal flora?

Protective microorganisms that can lead to opportunistic infections if disrupted.

What is opsonization?

The process of tagging pathogens for phagocytosis.

What are the characteristics of innate immunity?

Immediate response, no memory, same response each time.

What constitutes the first line of innate immunity?

Skin, mucous membranes, cilia, and bodily fluids like tears.

What constitutes the second line of innate immunity?

Phagocytes, NK cells, complement proteins, and inflammatory responses.

What are neutrophils?

The first responders in the immune system, primarily involved in phagocytosis.

What is unique about monocytes compared to other phagocytes?

Monocytes circulate in blood and mature into macrophages in tissues.

What role do eosinophils serve in the immune system?

They combat parasites and are involved in allergic reactions.

What are basophils and mast cells primarily known for?

Releasing histamine during allergic reactions.

What function do dendritic cells serve?

They are the most potent antigen-presenting cells, linking innate and adaptive immunity.

What is the primary function of natural killer (NK) cells?

Kill infected or tumor cells without prior sensitization.

What are the signs of inflammation?

Redness, heat, swelling, and pain.

What role does histamine play in inflammation?

It induces vasodilation and increased permeability of blood vessels.

What is diapedesis in the context of inflammation?

The process in which neutrophils squeeze through vessel walls to reach tissue injury.

What is chemotaxis?

The movement of white blood cells toward chemical signals at an infection site.

What is phagocytosis?

The process through which cells ingest and destroy pathogens.

What are the major functions of the complement system?

Opsonization, inflammation, cell lysis, chemotaxis, and immune complex clearance.

What triggers the classical pathway of the complement system?

It is triggered by IgM or IgG antibodies bound to antigens.

What distinguishes the alternative pathway?

It is antibody-independent and triggered by pathogen surfaces.

What initiates the lectin pathway?

Mannose-binding lectin binding to microbial surfaces.

What is the most abundant component of the complement system?

C3 is the most abundant component and central to all pathways.

What is the MAC in the complement system?

C5b-9, which leads to cell lysis.

How does complement relate to transfusion reactions?

ABO incompatibility activates the classical pathway leading to hemolysis.

What are the responsibilities of Canadian Blood Services?

Collecting, testing, processing, and distributing blood and managing stem cell registry.

What are the eligibility criteria for blood donors?

Must be at least 17 years old and weigh at least 110 lbs.

What are the hemoglobin requirements for blood donors?

Women must have ≥125 g/L and men must have ≥130 g/L.

What are temporary deferrals for blood donation?

Include tattoos/piercings, transfusions, pregnancy, dental surgery, and recent travel to Zika-infested areas.

What are some causes for indefinite deferrals for blood donation?

IV drug use and risk factors for CJD.

What are permanent deferrals for blood donation?

HIV, Hepatitis, and Ebola.

What types of blood donations are there?

Allogenic, autologous, directed, and designated donations.

What are packed RBCs stored at?

Stored at 1–6°C with a shelf life of 42 days.

What is the purpose of platelets in blood products?

To aid in clotting; stored at 20–24°C with a shelf life of 7 days.

What temperatures are plasma and cryoprecipitate stored at?

Plasma is frozen at ≤ −18°C, while cryoprecipitate is also stored at that temperature.

What is the main function of packed RBCs?

To raise hemoglobin levels by approximately 10 g/L.

What process is used to rapidly prepare whole blood components?

The buffy coat method separates RBCs, plasma, and platelets.

What is the filtration method used for?

To process RBCs along with plasma.

Why is irradiation used in blood transfusion?

To prevent transfusion-associated graft-versus-host disease (TA-GVHD).

What is the storage requirement for neutrophils?

They are kept at 1–6°C.

What defines the neutrophil's primary role?

They are the most abundant WBC and act as first responders to infections.

How long do neutrophils usually live?

A few hours to days.

What do neutrophils use to kill pathogens?

Phagocytosis, degranulation, and NETs (neutrophil extracellular traps).

What is the lifecycle of monocytes in relation to macrophages?

Monocytes circulate in the blood and migrate to tissues to become macrophages.

How do eosinophils affect parasites?

They contain major basic protein that is toxic to parasites.

What is the role of basophils in allergic responses?

Release histamine and are key players in type I hypersensitivity.

What is the function of dendritic cells in immunity?

They capture antigens, migrate to lymph nodes, and activate T-cells.

What triggers the inflammatory response?

Tissue injury leading to the release of histamine, prostaglandins, and cytokines.

What is the sequence of events during inflammation?

Tissue injury, vasodilation, increased permeability, diapedesis, chemotaxis, phagocytosis.

What are the key components involved in the inflammatory response?

Neutrophils, macrophages, and cytokines.

How does the innate immune system respond to pathogens?

Uses immediate defense mechanisms with no memory and the same response each time.

What are the distinct characteristics of adaptive immunity?

Highly specific, develops memory with each exposure, and has a slower initial response.

What produces antibodies in the immune system?

B-cells are responsible for antibody production in humoral immunity.

How do CD4+ helper T-cells function in adaptive immunity?

They coordinate the immune response and activate other immune cells.

What does MHC Class I present?

Endogenous antigens to activate CD8+ cytotoxic T-cells.

What does MHC Class II present?

Exogenous antigens to activate CD4+ helper T-cells.

What is the difference between the primary and secondary immune response?

Primary response is slow and weak; secondary response is fast and strong due to memory.

What type of immunity is effective against intracellular pathogens?

Cell-mediated immunity, primarily driven by T-cells.