Fundamentals of Immunology Flashcards
The body’s immune system is…
a complex and integrated network of cells, tissues, organs, mechanical barriers, and secreted molecules, all working together to protect the body.
Three Main Functions of the Immune System
Defense
Himeostasis
Surveillance
• The immune system detects abnormal cell growth, such as tumor formation or cancer, indicating a defect in the body’s ability to regulate cell growth.
Surveillance
• The immune system helps maintain balance in the body by stopping immune responses once a pathogen is eliminated. This ensures normal body cells aren’t harmed by the immune response.
Homeostasis
• Prevents entry of infectious agents: The immune system helps stop pathogens from entering the body. If pathogens do enter, the system eliminates them.
Defense
Four Key Components of the Immune System
- Cells and tissues of the immune system
- Monocyte-Macrophage cell system
- T lymphocytes
- B lymphocytes
Cells and Tissues of the Immune System
• Components: Includes the (3)
• These form the first line of defense, preventing the entry of pathogens.
skin
mucous-secreting cells
enzyme-producing cells
• Function: Acts as antigen-presenting cells (APCs), playing a critical role in immunity by identifying and responding to foreign pathogens.
Monocyte-Macrophage Cell System
are essential in cellular immunity, maturing in the thymus and playing a critical role in immune responses.
T cells
are central to humoral immunity and are responsible for producing antibodies that target extracellular pathogens.
B cells
Cells of IS
Coming from the same stem cell, but are going to differentiate into two:
lymphoid stem cell
myeloid progenitor cell
MYELOID PROGENITOR CELL
Neutrophil
Eosinophil
Basophil/ Mast cell
Monocyte (Dendritic cell/ Macrophage)
LYMPHOID STEM CELL
B cell progenitor (Plasma cell/ Memory cell)
T cell progenitor (T helper/ T cytotoxic)
Natural killer cell
• Most numerous granulocytes.
They are active during bacterial infections and migrate to infected tissues to carry out their function.
Neutrophils
• Contain major basic proteins, essential for fighting off parasites.
Eosinophils
Found in the blood, they release histamine, which is involved in initiating hypersensitivity reactions.
Basophils
Found in tissues, they are involved in hypersensitivity reactions and contribute to allergic responses.
Mast Cells
Monocytes: These cells circulate in the blood and can differentiate into:
Macrophage
Dendritic cell
- Engaged in phagocytosis to digest foreign material and pathogens.
- Act as antigen-presenting cells. They capture antigens, break them down, and present them to T cells to trigger an immune response.
Macrophages
Dendritic Cells
- B cells: Mature in the bone marrow and are essential for______ immunity.
- T cells: Mature in the thymus and play a role in_____ immunity.
- Natural Killer (NK) Cells: These cells are responsible for killing infected, foreign, or tumor cells by releasing______
humoral
cellular
cytotoxic chemicals.
• Activate macrophages and B cells through the secretion of cytokines.
• Help dendritic cells and macrophages present antigens to initiate specific immune responses.
T Helper Cells (Th cells)
• Release cytotoxic chemicals to kill infected cells, foreign cells, and tumor cells.
T Cytotoxic Cells (Tc cells)
Activation of B cells occurs when antigen-binding triggers the transformation of B cells into_____, which produce antibodies.
plasma cells
Humoral Immunity:
• ______ play a vital role in humoral immunity by producing antibodies that neutralize pathogens.
• Once activated, B cells become plasma cells, which produce a variety of ______ essential for immune defense.
B cells
antibodies/immunoglobulins
B Lymphocyte Activation and Function
- B Cell Activation:
• Antigen Binding: B cells have surface antibodies (_____ and _____) that bind to specific antigens.
• T Helper Cells: In addition to direct antigen binding, B cells can be activated by chemical signals from T helper cells. These signals trigger B cells to become_____, which release antibodies. - Antibody Production:
• Once B cells differentiate into plasma cells, they produce_____
IgM and IgD
plasma cells
antibodies
B cell
Role in Humoral Immunity:
• Produce antibodies that recognize and neutralize antigens.
• Antibodies are essential proteins for immune defense.
B Lymphocyte Activation
Surface Receptors: B cells have
_______ and ______ on their surface.
When antigens bind to these receptors, B cells become_______, leading to
antibody secretion
Alternatively,______ cells release chemical signals to activate B cells into plasma cells.
IgM and IgD
plasma cells
T helper
Activate macrophages and B cells via cytokine secretion.
Serve as the cells where APCS (dendritic cells, macrophages) present antigens.
Upon antigen detection, they elicit
specific immune response.
T Helper Cells (Th Cells):
Release chemicals to destroy:
Infected cells
Foreign cells
Tumor cells
Natural Killer Cells (NK Cells)
Types of immunity
Innate
Adaptive
Always consistent regardless of the type or amount of pathogen.
Governed by the same regulatory mechanisms.
Does not have immunologic memory.
Responds to all pathogens in the same way
Innate immunity
First line if defense
Skin
Mucosal lining
Other physiological factors that contribute to be first line of defense:
■ Hydrochloric acid in the stomach
■ Pseudostratified ciliated columnar
epithelium of the respiratory tract
(produces mucus)
■ Flushing action of urine
■ Unsaturated fatty acids (skin)
■ Sweat, tears, and saliva
■ commensal normal flora
Second line of defense
Inflammation
Inflammation
Results in 3 specific events:
■ Increased blood supply in the
area
■ Increased capillary permeability
■ Migration of leukocytes
Inflammation
The 3 events → manifest symptoms which include: (4)
■_______ → led to increased
blood flow in the area →_______ (increased temperature)
■_______
● is manifested by edema
Pain, heat, redness, and swelling
Vasodilation
Redness and Heat
Swelling
Features:
Develops immunologic memory and specificity in response to antigens.
Can differentiate between self and
non-self antigens.
Adaptive (Specific) Immune Response
Adaptive immunity
Involves two key mechanisms:
1.__________: Production of
antibodies by B-lymphocytes.
2._________: Actions of T-lymphocytes.
Humoral Immunity
Cell-Mediated Immunity
_______
B-lymphocytes are activated to become plasma cells.
Plasma cells produce antibodies capable of recognizing and neutralizing specific antigens.
_________
T-cells recognize antigens presented by antigen-presenting cells and initiate a specific immune response.
Antibody Production (Humoral Immunity)
T-Cell Actions (Cell-Mediated Immunity):
Substances capable of provoking a specific immune response.
If an antigen elicits an immune response, it is called an______.
ANTIGENS
immunogen
Role:
Stimulate antibody formation.
Initiate the development of cell-mediated immunity.
Antigen
Characteristics of Immunogens
Foreigness
Molecular size
Molecular complexity and composition
Route of inoculation and dose
Molecular Size:
Antigens with a molecular weight of_______ are better immunogens.
more than 10,000 daltons
______: Best form of antigens due to their complexity, making them effective in inducing an immune response.
_______: Less effective than proteins but still capable of inducing a response.
Proteins
Carbohydrates and Lipids
_________: Glycolipids that act as effective immunogens.
_________: Highly protein-based and strong immunogens.
Can lead to complications such as miscarriage if this blood type of the mother is incompatible with the baby.
ABO Antigens
Rh Antigens
_______: Most effective in inducing an immune response (e.g., through blood transfusion).
Intravenous Route
Recognized as foreign by the immune system.
Small regions within the immunogen molecule.
Also known as_______.
EPITOPES
antigenic determinants
Key Characteristics:
Unique Configurations: Allow recognition by a corresponding antibody.
Epitope
Multiple Epitopes:
A single antigen can have multiple epitopes.
Each epitope can elicit the production of a specific_____.
Cross-Reactivity:
Antibodies produced for different epitopes may ______ if these epitopes share a common determinant.
antibody
cross-react
Derived from another individual of the same species.
In Immunohematology and Blood Banking (IHBB):
Refers to blood from a different individual that may share the same blood type as the recipient.
Allogeneic Antigens
Derived from an individual’s own self.
Always tolerated by the immune system because they are recognized as self-antigens.
Autologous Antigens
If the immune system fails to recognize self-antigens, it can mistakenly attack them, leading to autoimmune conditions.
Autoimmune Response
Blood is collected from an individual and later transfused back into the same individual.
Commonly done for individuals with rare blood types.
Blood is donated for personal use only, not for others.
Autologous Transfusion
Chemical Structures: Embedded in or protruding from red blood cells (RBCs), white blood cells (WBCs), and platelets.
Determined by the inheritance of various blood group genes.
BLOOD ANTIGENS
Key Facts:
______Blood Group Systems recognized globally.
______Unique Red Cell Antigens are officially recognized by the American
Association of Blood Banks (AABB).
Every individual has a unique set of red cell antigens determined through______.
29
250
genetic inheritance
Common Forms of Blood Antigens
Glycolipids
Glycoprotein
Protein
Common Forms of Blood Antigens
Glycoproteins:
Example:______
Glycolipids:
Examples: _____(4)
Proteins:
Examples: ______ (3)
HLA system
ABH, Lewis, Ii, and P blood group systems
Rh, M, and N blood group systems
are specific proteins produced in response to a particular antigen, crucial for the immune defense.
Antibodies
Types of Antibodies:
Gamma (IgG)
Alpha (IgA)
Mu (IgM)
Epsilon (IgE)
Delta (IgD)
Characteristics of Antibodies
Size
Biologic function
Biochemical properties
Serological activity
Antibodies
Size
Monomeric Units: Some antibodies are composed of a single monomeric unit, while others have multiple units.
Smallest Antibodies: ________ (3)
These are monomers (single-unit structures).
_____: Can be monomeric (found in the serum) or dimeric (found in secretions).
Largest Antibody:
______: A pentamer (made up of five antibody units).
IgG, IgE, IgD
IgA
IgM
Antibodies
Biologic Function
Determined by the______ of the antibody.
_____ provide antibodies with unique features for specific biological functions.
The ______ determines the antibody class.
heavy chains
_____: Found in secretions like saliva, mucus, and tears.
Other antibodies (e.g.,_______) are primarily found in the serum
IgA
IgG, IgM, IgE
Light Chains:
Two types:
Kappa and Lambda
Antibodies
Biochemical Properties
______: Responsible for antigen binding.
______: Provides functional uniqueness
Variable Region
Constant Region
Antibodies
Attachment to specific cells:
___: Attaches to basophils and mast cells.
___: Found on the surface of B lymphocytes.
___: Mainly found in the serum.
___: Present on the surface of B cells.
___: Found in secretions.
IgE
IgD
IgG
IgM
IgA
______:
Composed of_____ bonds.
Provides flexibility for the antibody molecule during antigen binding.
Hinge Region
disulfide
_______: Splits the antibody into three fragments:
Two Fab (antigen-binding fragments).
One Fc (fragment crystallizable).
_____: Splits the antibody into two fragments:
One Fab.
One Fc.
Papain
Pepsin
Antibodies
Clinical Relevance in Hematology
Focus on_____ and_____:
These antibodies are of high clinical significance.
They are produced when red cells with foreign antigens (absent in the recipient) are introduced.
Essential in blood transfusion compatibility and immune response evaluation.
IgG and IgM
Immunoglobulin Mu (IgM)
General Characteristics
Largest Antibody:
Consists of five basic units, forming a______.
Units are joined by a______, composed mainly of disulfide bonds.
Location:
Restricted to the_____ space due to its large size.
Despite this, it efficiently activates the_______.
Percentage in the Immunoglobulin Pool:
Constitutes_____% of the total immunoglobulin population.
pentamer
J chain
intravascular
classical complement pathway
5–10
IgM
Functions and Properties:
IgM activates______ more efficiently than IgG.
Requires only____ IgM molecule to initiate the classical pathway.
complement; one
Primary Immune Response:
First antibody produced during the primary immune response to an antigen.
IgM
Saline Agglutinins:
It causes visible agglutination of cells suspended in saline.
Reacts at room temperature (22–24°C) or lower, making it a cold-reacting antibody.
IgM
IgG
Most Abundant Antibody:
Comprises____% of the total immunoglobulin population.
Ability to Cross the Placenta:
IgG possesses Fc receptors, enabling placental transfer.
80
IgG
Advantage: Protects the fetus by transferring maternal immunity.
Disadvantage: If produced against fetal red cell antigens, it may lead to________
Hemolytic Disease of the Fetus and Newborn (HDFN).
IgG
Complement Activation:
Activates complement but is less efficient than IgM.
Requires____ IgG molecules to initiate the classical complement pathway
Secondary Immune Response:
Predominant antibody in the secondary immune response.
2
Clinical Significance:
Most clinically significant in blood banking.
Reacts at 37°C (body temperature) and can activate complement.
Causes indirect agglutination and hemolysis.
Reactivity Enhancement:
Requires reagents like antihuman globulin for visible agglutination
IgG
IgG that cannot cross the placenta
IgG2
Steps in Antibody Formation (From Hemolytic Transfusion Reactions)
1.______ – slow progress of antibody production
2.______– happens the second time the patient encounters the same antigen
SENSITIZATION
FASTER PRODUCTION OF ANTIBODIES
Cause
Most commonly caused by incompatibility in the Rh blood group system.
Occurs when the baby inherits the Rh antigen from the father, which is absent in the mother.
Hemolytic Disease of the Fetus and Newborn (HDFN)
Hemolytic Disease of the Fetus and Newborn (HDFN)
Mechanism
First Pregnancy (Safe):
Initial exposure to fetal Rh antigens through_____ circulation.
Leads to_____ of the mother’s immune system.
Baby survives but may appear_____ due to hemolysis (bilirubin production).
Second Pregnancy (Unsafe):
Mother’s immune system recognizes the Rh antigen faster due to memory.
Produces IgG antibodies, which:
Cross the placenta.
Attach to fetal red cells.
Activate complement, causing hemolysis and potential fetal death.
fetomaternal circulation ; sensitization; jaundiced
The ______forms when antigens bind to antibodies through non-covalent forces, ensuring specificity and biological interaction.
antigen-antibody complex
antigen-antibody complex
Binding Mechanisms:
_________: Ionic attraction between oppositely charged molecules.
_________: Interaction between negatively charged groups (e.g., nitrogen, oxygen) with a hydrogen atom.
_________: Weak attractions between the electron cloud of one atom and the protons in the nucleus of another.
_________: Weak bonds formed by the exclusion of water from the antigen-antibody interface.
Electrostatic Forces
Hydrogen Bonds
Van der Waals Forces
Hydrophobic Forces
_______
Tendency of an epitope to combine with the antigen-binding site of an antibody molecule.
_______
Strength of the bond between the antigen and the antibody, representing overall binding force.
Affinity
Avidity
A group of serum proteins that play a crucial role in:
Antigen clearance.
Cell lysis.
Vasodilation.
Complement System
Complement System
_______: Circulate in an inactive or pro-enzyme state.
_______: Converts into active enzymes that amplify immune responses.
Inactive State
Activation
Functions of the Complement System
Opsonization
Anaphylaxis
Lysis
Chemitaxis
Coats foreign material with complement proteins to enhance phagocytosis.
Promotes the release of enzymes from neutrophils.
Opsonization
Increases smooth muscle contraction and induces inflammation.
Anaphylaxis
Attracts platelets and phagocytes to the site, initiating an immune response.
Chemotaxis
Three Pathways
- Classical Complement Pathway
- Alternative Pathway
- Mannose-binding lectin (MBL) Pathway
ANTIBODIES THAT CAN ACTIVATE COMPLEMENT
● IgM
● IgG1
● IgG2
● IgG3
Classical Pathway
Initiated by______
Alternative Pathway
Triggered by______ without antibody involvement.
Mannose-Binding Lectin (MBL) Pathway
Activated by_____ residues on microbial surfaces.
antigen-antibody interaction
pathogen surfaces (microbial surfaces or antibody molecules)
binding mannose
Non-Activating Antibodies:
IgG4, IgA, IgE, IgD
Membrane Attack Complex (MAC)
Formation:
C5b binds to C6, C7, C8, and C9.
Resulting structure:_____
C5b6789
