Innate Immunity Overview

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Questions and Answers

What role does lysozyme play in the body's defense mechanisms?

It regulates body temperature.

It traps microbes and debris.

It breaks down bacterial cell walls. (correct)

It inhibits the production of mucus.

How does the acidic environment of the stomach contribute to microbial control?

It kills most microbes due to low pH. (correct)

It enhances mucus production.

It neutralizes all types of bacteria.

It helps in digestion of proteins.

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

To maintain moisture levels.

To trap microbes and debris. (correct)

To facilitate ciliary movement.

To aid in gas exchange.

What mechanism helps expel dust and microbes from the lower respiratory tract?

Ciliary escalator. Signup and view all the answers

Which body fluid contributes to flushing mechanisms that prevent microbial colonization?

Urine. Signup and view all the answers

What is the role of the epiglottis in protecting the respiratory system?

To prevent food and microbes from entering the larynx. Signup and view all the answers

What is one function of commensal bacteria in the vagina?

To produce lactic acid, maintaining acidity. Signup and view all the answers

What is the primary purpose of inflammation?

To terminate infection and restore tissue Signup and view all the answers

Which sign of inflammation is characterized by swelling?

Tumor Signup and view all the answers

How does peristalsis contribute to microbial defense?

By facilitating the movement of food and expelling waste. Signup and view all the answers

What role do cytokines play in the inflammatory response?

Attract phagocytes to the site of inflammation Signup and view all the answers

During which step of the inflammatory response do phagocytes migrate to the affected area?

Phagocyte migration and phagocytosis Signup and view all the answers

Which of the following is NOT a hallmark sign of inflammation?

Necrosis Signup and view all the answers

What substance is released from injured cells that causes vasodilation?

Histamine Signup and view all the answers

What is the role of phagocytes in the inflammatory response?

To engulf and destroy invading pathogens Signup and view all the answers

Which statement about tissue repair is true?

It replaces dead or damaged cells after injury. Signup and view all the answers

Which cytokines stimulate the synthesis of acute phase proteins in the liver?

IL-1, IL-6, and TNF Signup and view all the answers

Which of the following pathways does not require antibodies for activation?

Alternative pathway Signup and view all the answers

What is the role of acute phase proteins in the immune response?

They activate complement and can kill bacteria. Signup and view all the answers

Which of the following best describes chronic inflammation?

It is less intense and more destructive. Signup and view all the answers

What complex forms the transmembrane channel that facilitates the membrane attack mechanism?

C5b678(9)n Signup and view all the answers

Which of the following endogenous factors can induce inflammation?

Tissue necrosis Signup and view all the answers

What is the function of chemokines in the immune response?

Chemotactic activity attracting immune cells Signup and view all the answers

What distinguishes the lectin pathway from other pathways of complement activation?

It is activated by microbial surface binding of host proteins. Signup and view all the answers

What distinguishes immunogens from regular antigens?

Immunogens can trigger an immune response. Signup and view all the answers

What is an epitope?

The smallest part of an antigen that can be recognized by immune receptors. Signup and view all the answers

Which type of tissue is primarily responsible for the liver's functions?

Parenchyma Signup and view all the answers

Which of the following statements regarding antigens is false?

Antigens cannot be recognized by the immune system. Signup and view all the answers

What happens if stroma cells are more active during tissue repair?

Scar formation takes place. Signup and view all the answers

Which of the following best describes the relationship between antigens and antibodies?

Each antibody recognizes specific epitopes on an antigen. Signup and view all the answers

Which characteristic is true for most antigens?

They can be recognized as foreign by the immune system. Signup and view all the answers

Which cellular components are primarily active in the remodeling phase of tissue repair?

Stroma cells Signup and view all the answers

Which of the following components is generally considered a poor immunogen on its own?

Nucleic Acids Signup and view all the answers

What is the primary role of normal flora in the body?

To compete with pathogens and inhibit their growth Signup and view all the answers

What type of antigen is formed from the body's own altered cells or fragments?

Autoantigens Signup and view all the answers

Which of the following statements is true regarding the second line of defense in the immune system?

Leukocytes include both granulocytes and agranulocytes Signup and view all the answers

How are exogenous antigens primarily taken up by Antigen-Presenting Cells (APCs)?

Phagocytosis Signup and view all the answers

What initiates the process of phagocytosis among phagocytes?

Chemotaxis towards site of infection mediated by signaling molecules Signup and view all the answers

Which MHC class is associated with the recognition of exogenous antigens by T-cells?

MHC-II Signup and view all the answers

Which cell type is primarily responsible for early phagocytosis during an infection?

Neutrophils Signup and view all the answers

What distinguishes a complete antigen from an incomplete antigen?

Ability to induce a response independently Signup and view all the answers

Which of the following is true about haptens?

They require a larger molecule to provoke a response Signup and view all the answers

What occurs during the digestion phase of phagocytosis?

The phagosome fuses with a lysosome to form a phagolysosome Signup and view all the answers

What is the role of opsonins in the immune response?

To facilitate the phagocytosis of pathogens Signup and view all the answers

What characteristic defines autoantigens?

They do not trigger an immune response under normal conditions Signup and view all the answers

Which T-cell protein is associated with the recognition of endogenous antigens?

CD8 Signup and view all the answers

What causes serious diseases like candidiasis following antibiotic use?

Overgrowth of pathogenic bacteria due to reduced normal flora Signup and view all the answers

Which type of leukocyte is primarily involved in the destruction of target cells via cytolysis?

Natural killer cells Signup and view all the answers

Study Notes

Innate Immunity

Innate immunity is the body's first line of defense against any microbial infection or foreign material
It provides protective mechanisms that don't require a prolonged induction period
It recognizes non-self structures but not self, avoiding autoimmunity
Pattern recognition receptors (PRRs) recognize pathogen-associated molecular patterns (PAMPs)
It detects immunological danger in the form of damage-associated molecular patterns (DAMPs)
Innate immunity is activated rapidly by microbes and subsequently activates adaptive immunity
Innate immunity is present from birth and is non-specific
It does not improve after exposure to antigens
It is available quickly and is antigen-independent
It has limited diversity and no immune memory
Physical barriers such as skin, form a hostile environment against microbes.
The dry, acidic surface of skin and continual loss of outer dead skin layers remove potential pathogens.
Cells of the stratum corneum create a tight barrier preventing toxins and bacteria from entering.
Sebaceous glands in dermis produce sebum to maintain pH between 3-5, inhibiting potential pathogen growth.
Sweat regulates body temperature to flush microbes and waste and lysozyme inhibits microbial growth
Mucous membranes are linings of the respiratory, digestive, and genitourinary tracts
Continuously produce mucus, a viscous glycoprotein which traps microbes and debris
Epithelial cells with inner connective tissue secrete mucus and prevent desiccation, trapping microbes.
Enzymes within mucus kill microbes, the acidic environment of the stomach also kills microbes.
Mucus-coated nose hairs trap microbes, the ciliary escalator in the lower respiratory tract pushes outward microbes; sneezing/coughing speeds the process
Epiglottis covers the larynx preventing food and microbes from entering.
Tears from lacrimal glands wash over the eye and drain into lacrimal ducts, containing lysozyme breaking down bacterial cell walls.
Urine flushes out microbes and contains uric acid, urea and lysozyme.
Acidic environment of vagina has lactic acid secreted by bacteria maintaining a pH 4.4-4.6 to kill microbes.
Saliva from salivary glands constantly cleans teeth and mouth, containing lysozyme and aggregate bacteria
Gastric juice with HCl, mucus, and enzymes with a low pH of 1.5-3 kills most microbes and toxins.
Small intestine mucus prevents attachment and entry. Pancreatic enzymes, bile, intestinal enzymes, and secretory IgA help.
M cells endocytose pathogens aiding presentation to B & T lymphocytes
peristalsis moves food, defecation eliminates waste, vomiting responds to toxins
Blood-brain barrier, blood-placenta barrier, and blood-thymus barrier protect privileged organs.
Recognition of signals indicates 'all is well' and prevents immune response against host tissues.

Normal Flora

"Normal microbiota" are microorganisms living on the body, inhibiting pathogen growth
Commensal microbes are not pathogenic except under specific circumstances.
The skin and gastrointestinal tract are colonized by over 500 microbial species
They defend their territory through physical advantage, nutrient competition, and inhibitory substances like acid and toxins.

Second Line of Defense

Formed elements of blood: platelets involved in blood clotting, erythrocytes transport oxygen/carbon dioxide, leukocytes include granulocytes and agranulocytes (e.g., neutrophils, basophils, eosinophils, monocytes, macrophages, dendritic cells, and natural killer cells.)
Phagocytes (e.g., neutrophils, monocytes, macrophages) perform phagocytosis, engulfing and destroying microbes through chemotaxis, adherence, ingestion, and digestion.

Soluble Factors

Acute-phase proteins increase plasma protein levels (e.g., C-reactive protein, mannose-binding protein) in response to cytokines produced by macrophages after exposure to microorganisms.
These proteins bind bacterial surfaces and activate complement.
Interferons (alpha, beta, gamma), chemokines (chemotactic activity), and enzymes (lactoperoxidase, lactoferrin, myeloperoxidase) are part of the soluble factors.
Complement (serum proteins C1-C30; C5b-C9 form membrane attack complex).

Complement Activation

Complement activation occurs through the classical, alternative, or lectin pathways.
Classical pathway is activated by antibodies, alternative pathway by microbial surfaces, and the lectin pathway by microbial surfaces.

Inflammation

Inflammation is a reaction to injury, from infection or physical/chemical trauma, to restore homeostasis.
Acute inflammation is rapid and resolves quickly (infection removed) while chronic inflammation persists longer.
Inducing factors include endogenous factors (tissue necrosis, hypersensitivity, bone fracture) and exogenous factors (mechanical injury, burns, chemical injury, and infectious agents).
Hallmark signs are tumor (swelling), rubor (redness), calor (heat), and dolor (pain).
Inflammatory response steps:

Vasodilation & increased vessel permeability, histamine released kins, prostaglandins, leukotrienes, cytokines, and clotting factors
Phagocyte migration and phagocytosis, phagocytes migrate to site of infection (diapedesis), phagocytic cells engulf microbes
Tissue repair, damaged tissue replaced, inflammatory response clears infection site and prevents infection, and phases are inflammatory, proliferative, and re-modeling

Antigens and Antibodies

Antigens are substances/molecules recognized as foreign by the immune system
Immunogens are antigens that trigger an immune response. All immunogens are antigens but not all antigens are immunogens.
Epitopes/antigenic determinants are the smallest portion of an antigen recognized by B and T receptors.
An antigen can have multiple epitopes.
An epitope on a monovalent antigen is different from a bivalent antigen.
A single antibody only recognizes one epitope at a time, not the whole antigen.
T-independent antigens are antigens capable of directly stimulating B cells to produce antibodies without the help of T helper cells.
These antigens have repeated epitopes, activating B cell clones for other antigens (polyclonal activation).
T-independent antigens are generally more resistant to degradation.
Antigens can be proteins, polysaccharides, nucleic acids, or lipids. Exogenous/endogenous antigens (external/internal body origin)
Autoantigens are normal proteins/protein complexes (DNA, RNA) recognized as non-self by the immune system.
These antigens cause issues when the immune system has lost immunological tolerance (e.g., Nucleoproteins, Nucleic acids).
Complete antigens have antigenic properties, to generate immune responses by themselves, high molecular weight.

Incomplete Antigens (Haptens)

Haptens are incomplete antigens, unable to induce an immune response on their own but can react with specific antibodies when combined with larger molecules (carrier molecules).
Haptens are often small molecules that become immunogenic after binding to a carrier molecule.
Haptenic determinants are new determinants created by the hapten.
The type of carrier molecule determines if the response will be T-independent or T-dependent.

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Description

Explore the fundamental aspects of innate immunity, the body's first line of defense against infections. This quiz covers its functions, mechanisms, and the role it plays in activating adaptive immunity. Test your knowledge on how innate immunity distinguishes between self and non-self structures.