Immunology Overview

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Questions and Answers

What is the main characteristic of innate immunity?

Always present from birth (correct)

Microbe-specific response

Memory component

Requires prior exposure to pathogens

Which statement accurately describes acquired immunity?

It responds specifically to antigens. (correct)

It operates without the involvement of antibodies.

It is present from birth and always active.

It provides immediate defense against infections.

What is the primary function of a healthy immune system?

To produce antibodies solely

To attack and destroy foreign material (correct)

To supply energy for cellular activities

To circulate nutrients throughout the body

Which component is found in serum but not in plasma?

Clotting factors Signup and view all the answers

What role do leukocytes play in the immune system?

They phagocytize microbes. Signup and view all the answers

What is the primary role of Bifidobacterium bifidum in the intestines of breast-fed infants?

To antagonize growth and prevent colonization by pathogens Signup and view all the answers

Which condition is Fusobacterium primarily associated with?

Colorectal cancer Signup and view all the answers

What are cationic peptides considered to be in immune defense?

Part of the second line of defense, innate immunity Signup and view all the answers

Which of the following complement pathways is the fastest?

Alternative pathway Signup and view all the answers

What is the composition of the complement system?

30 heat-labile blood proteins Signup and view all the answers

Which type of leukocyte is primarily involved in the destruction of large eukaryotic pathogens?

Eosinophils Signup and view all the answers

What is the main function of T-cells in the immune system?

Cellular immunity Signup and view all the answers

Which physical barrier helps to prevent microbial invasion through its waterproof properties?

Skin Signup and view all the answers

What role do normal flora play in innate immunity?

Preventing overgrowth of pathogenic microorganisms Signup and view all the answers

Which of the following factors does NOT directly influence the efficacy of defense mechanisms in the immune response?

Socioeconomic status Signup and view all the answers

Which structure in the respiratory tract is primarily responsible for trapping pathogens larger than 10 micrometers?

Cilia Signup and view all the answers

What is the primary role of basophiles in the immune response?

Inflammation and allergic responses Signup and view all the answers

Which part of the genitourinary tract can be colonized by bacteria?

Urethra Signup and view all the answers

What is the primary role of chemotaxis in the inflammatory response?

To attract phagocytes to the site of infection Signup and view all the answers

How does opsonization enhance the immune response?

By coating microorganisms with antibodies to facilitate adherence Signup and view all the answers

Which of the following is NOT a classic sign of localized inflammation?

Coughing Signup and view all the answers

What effect do pyrogens have on the body during a fever?

They signal the hypothalamus to adjust the body's thermostat Signup and view all the answers

During localized inflammation, which step follows the process of vasodilation?

Phagocyte Migration Signup and view all the answers

What role do complement proteins play in the immune response?

They help in binding and cleaving specific microbes. Signup and view all the answers

Which sugar is specifically mentioned as present in many bacterial cell walls and triggers complement activation?

Mannose Signup and view all the answers

What is the primary outcome of all complement activation pathways?

Formation of the membrane attack complex (MAC). Signup and view all the answers

What type of response does IL-1 promote?

Upregulation of inflammatory response. Signup and view all the answers

Which type of cytokine is primarily produced in response to viral infections?

Interferons (IFN) Signup and view all the answers

What effect does IL-10 have on the immune response?

Downregulates inflammation. Signup and view all the answers

Which type of cell does IL-17 primarily target?

CD-4 T cells Signup and view all the answers

How do cytokines facilitate communication between immune cells?

As soluble proteins or glycoproteins. Signup and view all the answers

Study Notes

Immunity

The body's ability to protect against diseases caused by microorganisms or their products.
Also called resistance.
Lack of immunity is called susceptibility.
Two types of immunity: innate and acquired.

Innate Immunity

Present at birth.
Not microbe-specific.
No memory component.
Always present.

Acquired Immunity

Must be acquired for each microbe.
Microbe-specific, responding to antigens.
Mediated by antibodies and T cells.
Slower to respond, but has a memory component.

Immunology

The study of the second and third lines of defense.
Main functions of a healthy immune system include:
- Surveillance of the body.
- Recognition of foreign material.
- Attack and destruction of foreign material.

Blood

Contains both non-specific and specific defenses.
Liquid tissue that circulates through arteries, veins, and capillaries.
Whole blood is made of blood cells suspended in plasma.
Serum is like plasma, but separated from clotted blood.

Blood Cells

Leukocytes (white blood cells) fight infection by phagocytizing microbes and killing infected cells, tumor cells, and worn-out red blood cells.
Types of leukocytes:
- Neutrophils: phagocytic and motile, active in initial stages of infection.
- Basophils: active in inflammation and allergic responses.
- Eosinophils: destroy large eukaryotic pathogens like helminths and fungi.
- Monocytes: mature into macrophages, which are phagocytic for microbes and dispose of worn-out red blood cells.
- Lymphocytes: two types, functioning in Adaptive Immunity:
  - T cells function in cellular immunity.
  - B cells function in humoral immunity (antibodies).
Red blood cells (erythrocytes): do not have a nucleus and carry oxygen, the most abundant cells in whole blood.
Platelets: not cells, required for blood clotting and function in inflammation.

Factors Affecting the Immune Response

Direct factors influence the efficacy of defense mechanisms:
- Nutrition.
- Physiology.
- Age.
- Genetics.
Indirect factors can also exert influence:
- Personal hygiene.
- Socioeconomic status.
- Living conditions.

Physical and Mechanical Defenses

Skin:
- Waterproof keratin.
- Acidic pH (sebum, sweat, organic acids from commensal S.a).
- Sheds, with microbiota.
Mucous membranes:
- Mucus resists penetration.
- Lysozymes (muramidase).
- Lactoferrin.
Respiratory tract:
- 10µm particles are trapped by cilia.
- Mucus traps and expels particles.
- Alveolar macrophages.
Gastrointestinal tract:
- Low pH.
- Digestive enzymes.
- Microbiota.
Genitourinary tract:
- Kidneys, ureters, and bladder are sterile.
- Distal portion of urethra (and vagina) can be colonized.
- Males have longer urethras, helping to exclude bacteria.
- Females have shorter urethras, making UTIs 14x more common.

Normal Flora Function in Innate Immunity

Normal flora prevent the overgrowth of pathogenic microorganisms.
Normal flora are antagonistic to pathogen growth through competition.
Normal flora can cause disease:
- Fusobacterium: anaerobic, non-spore forming, Gram-negative bacteria that can cause gingivitis, IBD, and ulcerative colitis. It can also be linked to colorectal cancer.

Chemical Mediators of Immunity

Part of the second line of defense (still innate).
Types:
- Cationic peptides: human origin, like cathelicidins, defensins, and histatin.
- Bacteriocins: produced by bacteria to kill other bacteria, like colicins (plasmid origin) which help E. coli lyse other strains of E. coli.
- Complement.
- Cytokines.

Complement

Consists of 30 heat-labile blood proteins.
Complement proteins are activated by cleavage of a pro-protein.
Main activation pathways:
- Classical pathway: discovered first but is slowest.
- Alternative pathway: discovered second, is faster.
- Lectin complement/Mannose-binding lectin pathway: discovered third, fastest as an alternative pathway.

Classical Pathway

Antibodies from the adaptive arm of the immune system bind to microbes.
Binding reveals amino acids on the antibody that recruit and cleave complement proteins.
Complement proteins can act as opsonins and connect the microorganism to the immune cell.

Alternative and Lectin Pathway

Molecules on the surface of bacteria bind complement proteins.
Mannose-binding protein (from host) binds to mannose on bacteria, triggering complement.

Regardless of Activation…

All complement pathways end with the membrane attack complex (MAC).
Activated complement proteins are inserted into the cell membrane, aiding in lysis.
Gram-negative bacteria are more susceptible to complement.

Cytokines

Chemical mediators that provide a way for immune cells to communicate.
Soluble, low molecular weight proteins or glycoproteins.
Types of cytokines:
- Chemokines: promote chemotaxis.
- Interleukins (IL): produced by leukocytes and act on other leukocytes.
- Interferons (IFN): produced in response to viral infections.
- Colony-stimulating factors (CSF): stimulate growth and differentiation of leukocytes.

Cytokine Target and Function

IL-1: Macrophages, T cells, B cells, NK cells; Up regulates inflammation response, fever, stimulates growth and differentiation of T cells, B cells, NK cells.
IL-10: Macrophages and neutrophils; Downregulates inflammation and cell response.
IL-17: CD-4 T cells, others?

Phagocytosis

Steps:
- Chemotaxis: attraction to the site of infection by chemical stimuli (endotoxins, microbial products, damaged tissue).
- Adherence: phagocyte plasma membrane interacts with the microbe; microbial capsules interfere with adherence. Opsonization (coating the microorganism with antibodies) promotes adherence.
- Ingestion: the microorganism is brought into the phagocyte in a membrane-bound vesicle called a phagosome.
- Digestion: the phagosome fuses with a lysosome, and the microbe is killed and digested.

Inflammatory Response

Classic signs and symptoms include:
- Redness (Rubor): increased circulation and vasodilation in injured tissue in response to chemical mediators and cytokines.
- Warmth: heat given off by the increased blood flow.
- Swelling: increased fluid escaping into tissue as blood vessels dilate—edema; WBCs, microbes, debris, and fluid collect to form pus, helping to prevent the spread of infection.
- Pain: stimulation of nerve endings.

Steps in Localized Inflammation

1. Vasodilation.
1. Edema.
1. Phagocyte migration.
1. Tissue repair.

Inflammatory Response: Fever

Systemic inflammatory response initiated by circulating pyrogens:
- Exogenous pyrogens: products of infectious agents (like LPS).
Phagocytes recognize pyrogens and secrete chemicals called cytokines.
Cytokines affect the body's internal thermostat located in the hypothalamus of the brain.
Benefits of fever:
- Inhibits multiplication of temperature-sensitive microorganisms.
- Impedes nutrition of bacteria by reducing available iron.
- Increases metabolism, stimulating immune reactions and protective physiological processes.

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Description

This quiz covers the fundamental concepts of immunology, focusing on the body's immune response, including innate and acquired immunity. It explores the roles of antibodies, T cells, and blood components in defending against diseases. Test your knowledge about how the immune system recognizes and destroys foreign materials.