Basic Immunology Lecture 1: Barriers to Infection

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Questions and Answers

What distinguishes innate immunity from adaptive immunity?

Innate immunity responds rapidly at birth. (correct)

Innate immunity can develop a stronger response on re-exposure.

Innate immunity is specific for each microbe.

Innate immunity has memory cells.

Which of the following is NOT a component of innate immunity?

Phagocytosis

Cytokines

Complement pathway

Antibodies (correct)

What is the primary role of skin in innate immunity?

Scanning for tumor cells.

Secreting antibodies to combat microbes.

Providing a mechanical barrier against microbes. (correct)

Producing cytokines to signal infection.

Which characteristic is associated with adaptive immunity?

Development of memory cells after an infection. Signup and view all the answers

Which of the following statements about the first line of defense is correct?

The first line of defense is the same for all microbes. Signup and view all the answers

Which type of cells play a crucial role in adaptive immunity?

Memory T and B cells Signup and view all the answers

How does adaptive immunity respond upon re-exposure to the same antigen?

It provides a stronger immune response. Signup and view all the answers

Which mechanism is NOT part of the innate immune response?

Specific targeting of pathogens. Signup and view all the answers

What is the primary function of cilia in the respiratory tract?

Removing secretions with trapped microbes Signup and view all the answers

How does the stomach create a hostile environment for most ingested microbes?

Through a highly acidic pH of 1 to 3 Signup and view all the answers

Which component in skin sweat is primarily responsible for breaking down the bacterial cell wall?

Lysozyme Signup and view all the answers

What role do commensal microbes play in the human body?

Serving as a natural defense against pathogens Signup and view all the answers

What does the term 'pathogenic dose' refer to?

The minimum number of organisms needed to establish an infection Signup and view all the answers

Which of the following is NOT a method of entry for pathogens into the host?

Exposure to sunlight Signup and view all the answers

What protective role do tears play for the eyes?

Washing away pathogens and containing antimicrobial components Signup and view all the answers

Study Notes

Basic Immunology (Lecture 1): Barriers to Infection

Immunology is the study of the immune system and its disorders
Immunology is divided into two main branches: Basic Immunology and Clinical Immunology
The main function of immunity is to prevent and fight against infection (outside invaders) and tumors (inside cellular abnormalities)
The immune system has two lines of defense: Innate (non-specific) and Adaptive (specific) immunity

Innate Immunity

First line of defense
Rapid onset, present from birth
Non-specific; same for all microbes
Limited specificity
No memory immune cells involved
Same response to re-exposure to antigens
Blocks entry of microbes, eliminates those that enter

Components of Innate Immunity

Barriers to infection (physical, mechanical, chemical, biological)
Innate immune cells
Cytokines (chemical mediators)
Acute phase proteins
Complement (alternative and Lectin pathway)
Phagocytosis
Inflammation

Adaptive Immunity

Second line of defense
Delayed response, develops after infection
Specific to each microbe (antigen)
Stronger response on re-exposure to same antigen
Relies on memory cells

Components of Adaptive Immunity

Adaptive immune cells (memory T and B cells)
Major blood proteins (Antibodies)
Complement (classical pathway)
Other Cytokines

Barriers to Infection: Non-Immunological Host Defenses

Physical Barriers:
Skin: Outermost epidermis (stratum corneum), tightly packed squamous cells, continuously detaching to remove microbes
Mucous membranes: Line body cavities (GIT, respiratory, genitourinary), goblet cells secrete mucus (traps microbes)
Mechanical Barriers:
Respiratory tract: Cilia rhythmically beat to remove secretions with trapped microbes
Urinary tract: Washing action of sterile urine during micturition
Eye: Washing action of tears during blinking
Intestine: Intestinal peristalsis removes microorganisms that can't colonize the intestine
Chemical Barriers:
Skin: Acidic pH (5.5), lysozyme (splits bacterial peptidoglycan), nucleases (destroy microbial genetic material), short unsaturated fatty acids (toxic to bacteria), defensins (act on bacterial cell membrane)
Stomach: Highly acidic environment (pH 1-3), kills most ingested microbes
Gastrointestinal tract: Digestive enzymes (e.g., pepsin)
Respiratory tract: Beta-defensins
Eye: Tears contain IgA and lysozymes
Biological Barriers (commensal microbes/normal flora):
Produce bacteriocins (antibiotics)
Competitive depletion of essential nutrients
Production of toxic by-products (e.g., vaginal lactic acid, pH 4)
Stimulate natural antibodies

Establishment of Infection

Pathogenic dose: Minimum number of microorganisms needed to cause infection
Microbial virulence: Microbial structures, proteins, enzymes, toxins that increase their ability to cause disease
Port of entry: Routes of infection (ingestion, inhalation, direct penetration)
Host immunity: Age extremes can have weak immune systems, making them more susceptible to infection

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Description

This quiz covers the foundational concepts of Basic Immunology, focusing on the body's barriers to infection. It explores the two main branches of immunology, the innate immune response, and the components involved in preventing infections. Perfect for students looking to reinforce their understanding of the immune system's first line of defense.