Immunohematology and Immunology Fundamentals

Vocabulary flashcards covering fundamental concepts in immunology and immunohematology, including cell types, antibody structure, immune responses, complement pathways, and serological agglutination testing.

Immunity

The process by which a host organism protects itself from attacks by both external and internal agents.

First line of defense

Physical and chemical barriers to infection, including unbroken skin, mucosal membrane surfaces, normal biota, mucus, lactic acid in sweat, saliva, tears, earwax, and stomach acid.

Natural Immunity

A non-specific defense mechanism (also referred to as innate immunity) consisting of cells like neutrophils, tissue basophils, and macrophages, as well as soluble substances such as complement, lysozyme, and interferon.

Interferon

A family of proteins that can block the replication of viruses in cells.

Acquired Immunity

Specific secondary immunity seen only in vertebrates that supplements innate immunity, is acquired by contact with a specific foreign substance, and exhibits memory that improves response with each exposure.

Humoral immunity

A branch of adaptive immunity that relies upon the production of antibodies by B cells and plasma cells.

B lymphocytes

Cells that mature in the bone marrow and function primarily to produce immunoglobulins.

Plasma cells

Non-motile, mature end-stage forms of B cells that each produce only one specific type of immunoglobulin.

Cell mediated immunity

A branch of immunity involving interactions of helper and cytotoxic T cells with target cells, functioning in delayed hypersensitivity, graft-v-host reactions, and allograft rejection.

Cytokines

Soluble substances produced by a subpopulation of T cells that function in growth promotion, differentiation, chemotaxis, and cell stimulation.

Natural Killer (NK) cells

Lymphocytes that protect against viruses and kill abnormal cells without needing prior stimulation by producing perforins to cause cell lysis.

Antigen Presenting Cells (APC)

Specialized cells, specifically macrophages, dendritic cells, and B cells, that sample the environment for antigenic molecules and process them for T-cell recognition.

Epitope

The specific part of a complex antigen (also called an antigenic determinant) with which an antibody reacts.

Haptens

Partial antigens that require a carrier molecule to elicit an immune response.

Antibodies

Glycoproteins made of 2 heavy chains and 2 light chains joined by disulfide bonds, featuring constant regions that determine class and variable regions that bind antigens.

IgM

A pentameric immunoglobulin containing a J chain, possessing a valence of 10 and molecular weight of 900,000 D, efficient at classical complement activation and detected at immediate-spin.

IgG

A monomeric immunoglobulin with a valence of 2 and molecular weight of 150,000 D, making up 70-75% of serum antibodies, capable of crossing the placenta, and detected via the antiglobulin test.

Primary response

An immune response elicited on first exposure to an antigen after a lag phase of 5 to 10 days, initially producing IgM followed by IgG.

Secondary response

An accelerated immune response elicited on second exposure within 1 to 3 days, producing sustained high levels of mostly IgG antibodies.

Alloantibodies

Antibodies produced after exposure to genetically different or non-self antigens of the same species.

Naturally occurring antibodies

RBC antibodies present without prior red cell exposure or pregnancy, mostly IgM cold agglutinins that react best at room temperature or lower.

Immune antibodies

RBC antibodies in serum resulting from transfusion or pregnancy, mostly IgG, reacting best at $37 proposal$ 37\n^\ncirc\text{C} and Coombs (AHG) phases.

Autoantibodies

Antibodies produced in response to self antigens that can react at various temperatures and potentially cause reactions in recipients.

Affinity

The strength of a single antigen-antibody bond produced by the sum of attractive and repulsive forces.

Avidity

The functional ability of serum antibody to bind to antigen.

Complement system

A collection of proteins that enhance immunologic functions including opsonization, lysis of pathogens, chemotaxis, inflammation, and clearance of immune complexes.

Classical pathway

A complement activation pathway initiated by antigen-antibody complexes.

Alternative pathway

A complement activation pathway initiated by foreign cell surface constituents such as pathogens or injured tissue.

Agglutination

In vitro antigen-antibody reactions that form visible clumping through sensitization and lattice formation.

Sensitization

The first stage of agglutination where antibody binds to antigen without visible clumping.

Lattice formation

The second stage of agglutination where antibody-coated cells cross-link to produce visible agglutination.

Zeta potential

The electrical distance between red blood cells created by charged ions, affecting lattice formation.

Prozone

A zone of antibody excess resulting in small antigen-antibody complexes and incomplete lattice formation.

Postzone

A zone of antigen excess resulting in small complexes and reduced agglutination.

Zone of equivalence

Optimal ratio of antigen and antibody concentrations that forms large, visible agglutinated complexes.

Forward grouping

Testing patient red blood cells with commercial anti-A, anti-B, and anti-D antisera to detect A, B, and D antigens.

Reverse grouping

Testing patient serum or plasma with reagent A1 and B red cells to detect ABO antibodies.

Crossmatch

A testing procedure combining donor red cells with patient serum or plasma to determine serologic compatibility prior to transfusion.

Anti-A1

A specific component of Anti-A that reacts with A1 cells but not A2 cells.

Anti-H

A weak, cold-reacting antibody found in the serum of group A1 and A1B individuals, identified using reagent from Ulex europaeus.

Bombay phenotype

A phenotype caused by homozygous silent hh genes, leaving the type-2 precursor structure unchanged due to lack of L-fucosyl transferase.