Immunology Overview and Immune System Basics

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Questions and Answers

What is the primary component of sebum that helps inhibit the growth of pathogens?

Saturated fatty acids

Unsaturated fatty acids (correct)

Triglycerides

Cholesterol

Which of the following white blood cells is classified as an agranulocyte?

Neutrophils

Monocytes (correct)

Basophils

Eosinophils

Which of the following statements accurately describes mast cells?

They possess specific enzymes that help distinguish them from basophils. (correct)

They contain primary granules but lack enzymatic activity.

They are included in granulocytes and secrete only histamine.

They originate only from the blood and never from tissue.

Which type of macrophage is found in the lungs?

Alveolar macrophages Signup and view all the answers

What percentage of total peripheral white blood cells do neutrophils typically represent?

50 to 70 percent Signup and view all the answers

Which of the following is a characteristic of primary granules in white blood cells?

Contain enzymes such as myeloperoxidase and elastase Signup and view all the answers

Which type of cell is specifically found in the liver as a macrophage?

Kupffer cells Signup and view all the answers

What is the primary function of eosinophils in the immune response?

To mediate allergic reactions and combat parasitic infections Signup and view all the answers

Which component is NOT found in the primary granules of eosinophils?

Major basic protein Signup and view all the answers

What role do transferrins play in the immune system?

They inhibit bacterial growth by reducing available iron. Signup and view all the answers

Which step does NOT belong to the process of phagocytosis?

Lymphokine activation Signup and view all the answers

Natural Killer (NK) cells are characterized by which of the following surface markers?

CD45 and CD56 Signup and view all the answers

Which of the following is NOT a function of the complement system?

Secretion of antibodies Signup and view all the answers

What type of response does a fever represent in the immune system?

A non-specific response characterized by raised body temperature Signup and view all the answers

Which mechanism is primarily involved in Antibody Dependent Cellular Cytotoxicity (ADCC)?

Recognition of targets via IgG antibodies Signup and view all the answers

What is the role of cytokines in the immune system?

They facilitate communication between immune cells. Signup and view all the answers

What distinguishes CD4 T lymphocytes from B lymphocytes in terms of antigen recognition?

Identify antigens only in the context of MHC molecules. Signup and view all the answers

Which of the following correctly describes the life span of effector cells produced by B lymphocytes?

3-5 days Signup and view all the answers

Which area in a lymph node is primarily associated with T cells?

Paracortex Signup and view all the answers

What is a primary function of secondary lymphoid organs?

Antibody production and trapping of infectious agents. Signup and view all the answers

Which of the following markers is associated with classic T cell identification?

CD2 Signup and view all the answers

What distinguishes Type I interferons from Type II interferons?

Type I interferons are nonimmune and produced during initial responses, while Type II are immune and produced during specific responses. Signup and view all the answers

Which interleukin primarily increases the number of mast cells in peripheral tissues?

IL-3 Signup and view all the answers

What is NOT one of the cardinal signs of inflammation?

Cytosis Signup and view all the answers

Which cytokine is primarily responsible for activating T helper cells and promoting B cell increase?

IL-1 Signup and view all the answers

Where are B lymphocytes primarily produced in humans?

Bone marrow Signup and view all the answers

Which of the following cells produce TNF-alpha upon encountering pathogens?

Macrophages Signup and view all the answers

What is the function of interferon gamma?

Enhance the activity of cytotoxic T cells. Signup and view all the answers

Which of the following is a characteristic of T lymphocytes?

They are produced in the thymus and bone marrow. Signup and view all the answers

What is the primary role of IL-4 in the immune response?

Promote class switching in B cells. Signup and view all the answers

Which sequence correctly identifies the secondary lymphoid organs?

Spleen, lymph nodes, tonsils Signup and view all the answers

What is the primary function of bone marrow in the lymphatic system?

Origin of all hematopoietic cells Signup and view all the answers

At which stage of B cell development is IgM expressed on the surface?

Immature B cell Signup and view all the answers

Which type of T cell is primarily responsible for limiting immune reactions?

T-suppressor cells Signup and view all the answers

Which of the following best describes a plasma cell?

A differentiated B cell producing antibodies Signup and view all the answers

What is the primary role of the thymus in the immune system?

Maturation of T cells Signup and view all the answers

What characterizes activated B cells?

Expression of CD25 receptor for IL-2 Signup and view all the answers

In which area of the thymus do immature T cells reside before maturation?

Cortex Signup and view all the answers

How do T cells identify antigens?

By recognizing antigens presented by APCs Signup and view all the answers

Which of the following correctly describes the transformation of activated B cells?

They differentiate into plasma cells Signup and view all the answers

What is the main activity of naive T cells in response to antigen exposure?

Differentiate into effector cells Signup and view all the answers

Study Notes

Immunology

Immunology is the study of molecules, cells, or organs and systems responsible for the recognition and disposal of foreign material.
It also examines how body components respond and interact, along with desirable and undesirable consequences of immune interactions.
It investigates ways to advantageously manipulate the immune system for disease protection or treatment.

Immune System

The immune system is a collection of cells, tissues, and molecules mediating resistance to infections.
Physiological functions include defense against infections, tumors, tissue grafts and newly introduced molecules.
The immune system can also harm cells and induce pathogenic inflammation.

Components of Immunity

Natural/Innate/Nonspecific Immunity

Provides protection against many different pathogens.
Present at birth.
Provides a standardized response for all pathogens.
Lacks memory; unable to remember prior exposure.
General response does not improve upon repeated exposure.
Recognizes foreign molecules via toll-like receptors (pattern-recognition receptors) interacting with pathogen-associated molecular patterns (PAMPs).

Acquired/Adaptive/Specific Immunity

Provides protection against specific pathogens.
Not present at birth.
Offers a diverse response to each antigen.
Has memory.
Specific response improves upon repeated exposure.
Recognizes foreign molecules via specific receptors interacting with corresponding epitopes.

Cells of the Innate and Adaptive Immune Systems

Diagram shows overlapping circles representing innate and adaptive immunity with various cell types: Mast Cells, PBMCs, Macrophages, Neutrophils, Dendritic Cells, Natural Killer Cells, Monocytes, B cells, T cells, and regulatory T cells.

Natural Immunity

First Line of Defense

Physical/Mechanical:
- Intact skin: physical barrier to pathogens; normal skin flora.
- Mucous membranes: line open body cavities; secretion of mucous.
- Cilia: line the respiratory tract; traps and propels harmful air particulates and airborne pathogens.
- Lacrimal apparatus: continual washing and blinking preventing microbes from settling on the eye surface.
- Saliva: washes microbes from teeth and mouth mucous membranes.
- Mucus: thick secretion trapping many microbes.
- Coughing and sneezing: expel foreign objects.
- Epiglottis: covers larynx during swallowing.
- Urination: cleanses urethra.
- Vaginal secretions: remove microbes from genital tract.
Biological/Chemical:
- Lysozyme (muramidase): abundant in secretions; damages bacterial cell walls.
- pH: inhibits growth of certain pathogenic bacteria and fungi.
- Sebum: contains unsaturated fatty acids inhibiting growth of certain pathogenic bacteria and fungi.
- Perspiration: contains lysozyme and acids; traps and propels harmful air particulates and airborne pathogens.

Second Line of Defense

Cellular Factors:
- Phagocytes: neutrophils, macrophages, monocytes, eosinophils.
- NK cells
- Basophils and Mast Cells.
Mast Cells: included in granulocytes; enzyme content distinguishes them from basophils (acid phosphatase, alkaline phosphatase, protease).
Monocytes: classfied as agranulocytes; phagocytes in blood; largest blood cell..
Monocytes (in the Blood) and Tissue Macrophages: (e.g., Kupffer cells in liver, alveolar macrophages/dust cells, microglial cells, dendritic cells, splenic/littoral macrophages, osteoclasts) located in various tissues and organs.
Granulocytes (WBC): Contain granules: primary granules with enzymes like myeloperoxidase, elastase; secondary granules with collagenase, lactoferrin, lysozyme; tertiary granules with gelatinase and plasminogen activator.
Eosinophils: Increased presence of allergens and parasitic infections; included in granulocytes; primary granules contain acid phosphatase and arylsulfatase; eosinophil-specific granules contain major basic protein, eosinophil cationic protein, eosinophil peroxidase, and eosinophil derived neurotoxin
Basophils: Included in granulocytes; increased if allergy present; granules are histamine, small amount of heparin

Function of Phagocytosis

Killing invading microorganisms/disposal of damaged or dying cells.
Removal of aging erythrocytes from spleen.
Removal of tissue debris from repairing wounds/embryonic tissues/cancer cells

Steps in Phagocyte Extravasation

A detailed diagram illustrating the steps in phagocyte extravasation.

Steps in Phagocytosis

A schematic diagram illustrating the steps involved.

Natural Killer Cells

Forms initial defense against aberrant cells (tumors and virally-infected cells).
Comprise 10-15% of circulating lymphocytes.
Identified by specific surface markers.
Known as Lymphokine-Activated Killer Cell when exposed to IL-2 and IFN gamma.
Antibody Dependent Cellular Cytotoxicity (ADCC); requires IgG molecule.

ADCC

Final mechanism of cellular cytotoxicity.
Cytotoxic potential of NK, Neutrophils, Macrophages, Eosinophils.
Mechanism of target cell killing involves lytic enzymes and mechanisms like perforin/granzymes/TNF. Diagrams are included showing these processes.

Humoral

Transferrins: Iron-binding proteins inhibiting bacterial growth by reducing available iron.
Complement System: More than 30 circulating glycoproteins functioning as anaphylatoxin, chemotaxin, opsonin and lysis.
Fever: Generalized response to infection with temperature elevation above basal (36.5-37.5°C). Stimulus is pyrogens, which augment host defenses.
Acute Phase Reactants: Plasma proteins increasing in concentration during chronic or intensive inflammation. Table 1-1 shows characteristics of acute-phase reactants (protein, time, increase, function).

Cytokines

Chemicals released by many body cell types enabling immune communication. Table provides specifics of various cytokines, their cellular sources, and primary targets.

Interferons

Family of glycoproteins with virus-nonspecific/host-specific antiviral activity. Type I interferons (NONIMMUNE) are initial responses to viral infections (e.g., interferon alpha from leukocytes, interferon beta from fibroblasts). Type II interferons (IMMUNE) are primarily components of the specific immune response against viral and other pathogens (e.g., interferon gamma produced by immunologically stimulated T cells).

Tissue Necrosis Factor

Tumor necrosis factor-alpha (TNFα) produced by macrophages, lymphocytes, and NK cells encountering bacteria, viruses, tumor cells, toxins and complement protein C5a.
TNF-beta produced by CD4 and CD8 positive cells after exposure to specific antigens.

Interleukin

IL-1 activates T helper cells, increases B cell numbers, activates vascular endothelium; causing fever and acute-phase protein synthesis and induces T cells to produce lymphokines.
IL-2 causes proliferation of activated T and B cells.
IL-3 increases mast cells in skin, spleen, and liver.
IL-4 induces proliferation of T cells and class switching from IgM to IgG and IgE.

Inflammation

Local response to tissue damage, series of biochemical and cellular changes for irritant elimination and damaged tissue repair. Detailed diagrams are included.

Cardinal Signs of Inflammation

The five cardinal signs: Rubor (redness), Calor (heat), Tumor (swelling), Dolor (pain), Functio laesa (loss of function) are described and illustrated.

Adaptive Immunity

Components: cellular (T lymphocytes, B lymphocytes, plasma cells)—and humoral (antibodies, cytokines).
Comparison of Types of Acquired Immunity: (Table 1-3) active/passive; natural/artificial—modes of acquisition, antibodies produced by the host, and durations of immune responses.

Lymphocytes

Key cells in immune response; 7-10 µm in diameter with large rounded nucleus; some cells may be indented.
Primary lymphoid organs—bone marrow (B lymphocytes), thymus (T lymphocytes).
Secondary lymphoid organs—spleen, lymph nodes, appendix, tonsils—and other mucosal-associated lymphoid tissue.

Primary Lymphoid Tissue

Central lymphoid organs are the thymus and bone marrow.
Details about these organs' functions relating to lymphocyte maturation, differentiation (e.g., of pro-B cells into mature B cells in the bone marrow, or T cell precursors in the thymus).

B Lymphocytes

Effector cells of humoral-mediated immunity.
Derived from progenitor cells through an antigen-independent maturation process in bone marrow and GALT (gut-associated lymphoid tissue).
Differentiate into plasma cells upon antigenic stimulation.
Stages of B cell development: pro-B, pre-B, immature B, and mature B cell. Specific markers (e.g., CD19, CD21, CD35, CD40, CD45). Cells undergo rearrangement of genes producing antibodies (e.g., IgM on surface at different stages.)
Activated B cells—antigen CD25 appears—end stage is becoming a plasma cell. Plasma cells have abundant cytoplasmic immunoglobulin.

T Lymphocytes

Cells involved in cellular immune response. Expression of specific T cell antigens depends on the maturation and activation stages. They have the ability to bind with sheep red blood cells (RBCs) forming rosettes (important diagnostic tool for identifying them). Have a longer life span than B cells. Subsets of T cells (e.g., T-helper, T-cytotoxic, T-suppressor) and their functions (e.g., Th1, Th2, TH17, etc.).

Subset of T Cells

Detailed functions of T helper cells (Th), cytotoxic T cells (Tc), suppressor T cells (Ts), and T-delayed type hypersensitivity cells (Tdth).

T cell maturation

A diagram showing the process of T cell maturation, highlighting the thymus' role, the involved cells, and cytokines that regulate this process.

Phases of T cell responses

The phases of T cell response including naïve T cells with no prior exposure to antigen—recognition of antigen in secondary lymphoid organs, stimulation and proliferation—becoming effector cells and memory cells—differentiation of effector cells—re-encountering antigen in circulation-performing effector function, release of cytokines. Diagram included.

Helper T cell CD4

Different helper T cell subtypes (e.g., Th1, Th2, Th17) and their respective functions (e.g., macrophage activation, B cell activation, extracellular bacterial and fungal control). Diagram included

T Lymphocytes, B Lymphocytes

Key differences between these cells: Effector & recognition mechanisms, development locations (Thymus vs BM).

Cellular & Humoral Immunity

Key differences: Antigens involved (CD2, CD3, CD4, CD8 vs CD19, CD20, CD21, CD40, MHC, etc.), End products following activation, life-span of activated cells.

Secondary Lymphoid Organs

Sites where mature T and B cells are stored until antigen or stimulus encounter. Spleen, lymph nodes, tonsils, Peyer's patches (gut-associated lymphoid tissue), Bronchus-associated lymphoid tissue (BALT).
Functions of these organs, e.g., standby areas for T cells, B cells and macrophages; trapping sites for infectious agents or their antigen-bearing products; antibody production, or production of immunocompetent T cells. Specific details of lymph node sub-sections.

Spleen

Largest secondary lymphoid organ.
Lymphatic filter in blood vascular tree.
Removes senescent red blood cells (RBCs) and inclusion bodies.
Major site of antibody (Ab) synthesis.
Responds to antigens introduced intravenously.

Virus

Small genetic material with a protein envelope incapable of independent reproduction.
Virion—Entire virus particle—nucleus of nucleic acid is surrounded by capsid (protein coat). Many also have a membrane (envelope) and protein spikes.

Life Cycle of Virus

A schematic illustrating the life cycle phases, including Attachment, Penetration, Uncoating, Gene expression and replication, Assembly, Release.

HIV and AIDS

Human Immunodeficiency Virus. Types HIV-1 (Global) and HIV-2 (Africa).
Family Retroviridae, subfamily Lentiviridae.
Preference for T Helper/Inducer Lymphocytes (CD4+).
Discovered by Luc Montagnier (1983) and Robert Gallo (1981)
Viral genome and gene products; including structural protein functions (p24, p18, p15, gp120, gp41, reverse transcriptase, RNAase, protease, integrase).
Diagrams describing HIV structure (immature, mature forms of the virus).

Mode of Transmission

Sexual contact, Blood Transfusion, Parenteral injection, Transplacental, Breastfeeding, Passage through infected birth canal.

Clinical Manifestation

Primary Stage: asymptomatic or lymphadenopathy.
Intermediate Stage: ARC → AIDS-related complex. Quantitative T-cell deficiencies with inverted CD4:CD8 ratio.
Final Stage (2-10 years post-infection): Syndrome of CD4 depletion—result in opportunistic infections—infection & cancers indicative of cell-mediated immunity defects.
Severe depletion of Helper–Inducer T lymphocytes when HIV replicates. Normal CD4:CD8 ratio → 2:1. AIDS patients → 0.5:1.

Antigens

Any molecular structure initiating antibody production; consisting of two sections (epitope & carrier).

Antibodies

Specific glycoproteins, produced by B lymphocytes or plasma cells, in response to antigenic stimulation. Also known as immunoglobulins or gamma globulins. Make up around 20% of the proteins in blood plasma. Part of adaptive or humoral immune response.

Functions of the Immunoglobulins

Bind antigens.
Fix complement.
Facilitate phagocytosis.
Neutralize toxins.

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Description

Explore the fundamentals of immunology, including the components and functions of the immune system. This quiz covers the distinctions between natural and innate immunity, as well as their roles in protecting the body from pathogens. Test your knowledge on how the immune system interacts with foreign materials.