Microbiology Study Guide: Infection, Innate Immunity, and Adaptive Immunity (Chapters 14-16)

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Chapter 14: Infection, Infectious Diseases, and Epidemiology

Key Terms and Definitions

Symbiosis: A close and long-term biological interaction between two different biological organisms. Types include mutualism, commensalism, and parasitism.
Anthphagocytic factors: Mechanisms used by pathogens to evade phagocytosis by host immune cells.
Opportunistic pathogen: Microorganisms that cause disease only when the host's defenses are compromised.
Reservoir: Any person, animal, plant, soil, or substance in which an infectious agent normally lives and multiplies.
Zoonoses: Diseases that can be transmitted from animals to humans.
Contamination: The presence of microorganisms on inanimate objects or surfaces.
Infection: The invasion and multiplication of microorganisms in body tissues, causing disease.
Virulence: The degree of pathogenicity of a microorganism.
Pathogenicity: The ability of a microorganism to cause disease.
Human carrier: An individual who harbors a pathogen without displaying symptoms, but can transmit it to others.
Teratogen: An agent or factor that causes malformation of an embryo.
Toxemia: The presence of toxins in the blood.
Vector transmission: The transfer of pathogens via an organism (vector), such as insects.
Disease/Morbidity: Disease refers to a disorder of structure or function; morbidity is the rate of disease in a population.
Etiology: The study of the cause of disease.
Koch's Postulates: Criteria used to establish a causative relationship between a microbe and a disease.
Fomites: Inanimate objects that can transmit infectious agents.
Epidemiology: The study of the distribution and determinants of health-related states in populations.
Incidence: The number of new cases of a disease in a population over a specific period.
Prevalence: The total number of cases of a disease in a population at a given time.
Endemic: A disease regularly found among particular people or in a certain area.
Sporadic: Occurring at irregular intervals or only in a few places.
Epidemic: A sudden increase in the number of cases of a disease above what is normally expected.
Pandemic: An epidemic that has spread over several countries or continents.
Index Case: The first documented patient in a disease outbreak.
Nosocomial Infection: Infections acquired in hospitals or healthcare settings.
Exogenous Nosocomial Infection: Infection from external sources in a healthcare setting.
Endogenous Nosocomial Infection: Infection from the patient's own microbiota.
Iatrogenic Nosocomial Infection: Infection resulting from medical procedures.
Superinfection: A new infection occurring on top of an existing one, often due to disruption of normal flora.

Types of Symbiotic Relationships

Mutualism: Both organisms benefit (e.g., Escherichia coli in the human gut).
Commensalism: One organism benefits, the other is unaffected (e.g., skin bacteria).
Parasitism: One organism benefits at the expense of the other (e.g., pathogenic bacteria).

Reservoirs of Infection

Human Reservoirs: Carriers of disease, symptomatic or asymptomatic.
Animal Reservoirs: Zoonotic diseases transmitted from animals.
Nonliving Reservoirs: Soil, water, and fomites.

Portals of Entry

Mucous membranes (respiratory, gastrointestinal, urogenital tracts)
Skin
Parenteral route (cuts, bites, injections)

Attachment to Host Cells

Adhesion: Microorganisms use adhesins (surface proteins) to attach to host cell receptors.

Manifestation of Disease

Signs: Objective evidence of disease (e.g., fever).
Symptoms: Subjective feelings (e.g., pain).
Syndrome: A group of signs and symptoms.
Asymptomatic: No noticeable symptoms.

Virulence Factors

Adhesion factors
Enzymes (e.g., coagulase, hyaluronidase)
Toxins (endotoxins, exotoxins)
Antiphagocytic factors
Capsules

What is the difference between endotoxins and exotoxins? Endotoxins are components of bacterial cell walls that are released upon cell death and have less specific systemic effects, while exotoxins are actively secreted proteins with specific effects on host cells and are more immunogenic.
List and describe the five stages of infectious disease?
Incubation - The time between exposure to the pathogen and the onset of symptoms.
Prodromal - The initial stage where vague and nonspecific symptoms begin to appear.
Illness - The stage where the disease is at its peak and symptoms are most severe.
Decline - The stage where symptoms begin to subside as the immune response effectively combats the pathogen.
Convalescence - The recovery phase where the body heals and returns to a normal state.
Biological vectors: Organisms that transmit pathogens and are part of the pathogen's life cycle (e.g., mosquitoes).
Mechanical vectors: Organisms that transmit pathogens without being infected (e.g., flies).
Whose job is it to track incidence and prevalence of disease? The primary responsibility for tracking diseases are on the public health agencies like CDC which is on the national level for the US.

Nosocomial Infections

12. Occur in healthcare settings due to exposure to pathogens, invasive procedures, or compromised immunity.
13. Iatrogenic: Directly caused by medical intervention.

21. What is the difference between mechanical vector transmission versus biological vector transmission? The primary distinction lies in the infection status of the vector and the developmental process of the pathogen. Mechanical vectors carry pathogens without infection, while biological vectors are essential for the pathogen's life cycle and actively participate in its transmission.

Table: Types of Nosocomial Infections

Type	Source
Exogenous	External environment (other patients, staff, equipment)
Endogenous	Patient's own microbiota
Iatrogenic	Medical procedures

Additional info:

Normal flora can prevent pathogen colonization by competing for nutrients and producing inhibitory substances.

Chapter 15: Innate Immunity

Key Terms and Definitions

Innate immunity: Non-specific defense mechanisms present from birth.
Dendritic cells: Antigen-presenting cells that initiate immune responses.
Sebum: Oily secretion that inhibits microbial growth on skin.
Lysozyme: Enzyme that breaks down bacterial cell walls.
Lacrimal apparatus: Produces tears containing lysozyme.
Microbiome: The community of microorganisms living in and on the body.
Leukocytes: White blood cells involved in immune defense.
Neutrophils: Phagocytic cells that ingest and destroy microbes.
Eosinophils: Defend against parasitic infections and mediate allergic responses.
Lymphocytes: Include B cells, T cells, and natural killer cells.
Phagocytosis: The process by which cells ingest and destroy pathogens.
Natural Killer Lymphocytes: Destroy infected or abnormal cells.
Interferons: Proteins that inhibit viral replication.
Complement system: A group of proteins that enhance immune responses.
Inflammation: A response to infection or injury characterized by redness, heat, swelling, and pain.
Acute: Short-term, rapid onset.
Chronic: Long-term, persistent.
Vasodilation: Widening of blood vessels.
Diapedesis: Movement of leukocytes out of blood vessels into tissues.
Pyrogen: Substance that induces fever.
Fever: Elevated body temperature as a defense mechanism.

1. Which of the following best describes the innate nonspecific immune system?

a. a targeted and highly specific response to a single pathogen or molecule

b. a generalized and nonspecific set of defenses against a class or group of pathogens

c. a set of barrier mechanisms that adapts to specific pathogens after repeated exposure

d. the production of antibody molecules against pathogens

2. Monocytes are agranular leukocytes that develop into macrophages.

(Hint: options are granular or agranular for the first empty slot)

3. From our Power Point, name one chemical or cell that can stimulate vasodilation is... Histamine

4. Name at least 2 locations were mucus-secreting membranes can be found in the human body. Nasal cavity and stomach lining

5. Explain the difference between the dermis and epidermis. The epidermis is the outer, avascular layer, while the dermis is the inner, vascular layer.

6. Which is not a leukocyte?

A. lymphocyte B. erythrocyte C. monocyte D. neutrophil E. eosinophil

7. What cells are fixed phagocytes in the epidermis? Langerhans cells

8. Describe how normal flora help protect the body from pathogens. Normal flora protect the body from pathogens by competing for resources and space, producing antimicrobial substances, and stimulating the immune system.

9. Which type of lymphocyte is involved in nonspecific immune defense?

A. T-cells

B. B-cells

C. Natural Killer (NK) cells

D. none of these lymphocytes are nonspecific

10. Which of the following serve as chemical signals between cells and stimulate a wide range of nonspecific defenses?

A. cytokines

B. antimicrobial peptides

C. complement proteins

D. antibodies

11. What is another name for white blood cells? leukocytes

12. Which of the following constantly sheds dead cells along with any microbes that may be attached to those cells?

A. epidermis

B. dermis

C. hypodermis

D. mucous membrane

13. What is phagocytosis (name all steps) and how is it involved in our body defending us from pathogens? Phagocytosis is the process where immune cells engulf and destroy pathogens in a multi-step process involving chemotaxis, adherence, ingestion, fusion with a lysosome, digestion, and elimination. This mechanism is essential for the innate immune system's defense against infection.

14. How is fever involved in immunology? If a fever gets too high, why is that dangerous? (I need an answer in terms of the specifics of what fever does to the immune system and what high fever can do to the cells in the body).

Fever helps the immune system by increasing the rate of metabolic processes and inhibiting the growth of some pathogens, but high fever is dangerous because it can denature essential body proteins and enzymes.

15. This term describes how the presence of normal flora bacteria discourage pathogens from becoming established? Competitive exclusion (or microbial antagonism).

This term describes the mechanism by which normal flora bacteria occupy space and consume resources, making it difficult for pathogens to become established. They also often produce substances that inhibit the growth of other microorganisms.

16. The muscular contraction of the intestines that results in movement of material through the digestive tract is called peristalsis.

17. Cilia are the hair-like appendages of cells lining parts of the respiratory tract that sweep debris away from the lungs.

18. Match each cell type with its description.

__C__natural killer cell A. stains with basic dye methylene blue, has large amounts of histamine in granules, and facilitates allergic responses and inflammation

__A___basophil B. stains with acidic dye eosin, has histamine and major basic protein in granules, and facilitates responses to protozoa and helminths

__D___macrophage C. recognizes abnormal cells, binds to them, and releases perforin and granzyme molecules, which induce apoptosis

__B____eosinophil D. large agranular phagocyte that resides in tissues such as the brain and lungs

20. Match each cellular defense with the infection it would most likely target.

___A___natural killer cell A. virus-infected cell

___C___neutrophil B. tapeworm in the intestines

___B___eosinophil C. bacteria in a skin lesion

21. What are interferons and when does your body release them? Interferons are signaling proteins released by cells in response to viral infections.

22. Which refers to swelling as a result of inflammation?

A. erythema

C. granuloma

B. edema

D. vasodilation

23. What type of inflammation occurs at the site of an injury or infection? Acute inflammation

24. The hypothalamus is the part of the body responsible for regulating body temperature.

25. Heat and redness, or erythema occur when the small blood vessels in an inflamed area dilate (open up), bringing more blood much closer to the surface of the skin.

Innate Immune System Features

Non-specific, immediate response to pathogens.
Includes physical barriers (skin, mucous membranes), chemical barriers (lysozyme, sebum), and cellular defenses (phagocytes, NK cells).

Phagocytosis Steps

Chemotaxis: Movement toward infection site.
Adherence: Binding to pathogen.
Ingestion: Engulfing pathogen.
Digestion: Enzymatic breakdown.
Exocytosis: Release of debris.

Table: Types of Leukocytes

Type	Function
Neutrophil	Phagocytosis of bacteria
Eosinophil	Defense against parasites
Basophil	Release histamine, mediate allergic responses
Macrophage	Phagocytosis, antigen presentation
Natural Killer Cell	Destroy virus-infected and tumor cells

Inflammation and Fever

Inflammation increases blood flow and immune cell access to infected tissues.
Fever is triggered by pyrogens and can inhibit pathogen growth.
Excessive fever can be dangerous due to protein denaturation and organ damage.

Additional info:

Normal flora protect against pathogens by occupying niches and producing antimicrobial substances.
Interferons are released in response to viral infection and activate immune cells.

Chapter 16: Adaptive Immunity

Key Terms and Definitions

Adaptive (Acquired) Immunity: Specific immune response developed after exposure to antigens.
Cell-mediated immune response: Involves T lymphocytes targeting infected cells.
Antibody immune response: Involves B lymphocytes producing antibodies.
B lymphocytes: Cells that mature in bone marrow and produce antibodies.
Plasma Cells: Differentiated B cells that secrete antibodies.
Antibody: Protein that binds to specific antigens to neutralize pathogens.
T lymphocytes: Cells that mature in the thymus and mediate cellular immunity.
Lymphatic system: Network of vessels and organs involved in immune responses.
Antigens: Substances that provoke an immune response.
Epitopes: Specific regions of an antigen recognized by antibodies.
MHC (Major Histocompatibility Complex): Proteins on cell surfaces that present antigens to T cells.
Cytotoxic T lymphocyte: Destroys infected or abnormal cells.
Helper T lymphocyte: Activates B cells and other immune cells.
Regulatory T lymphocyte: Suppresses immune responses to prevent autoimmunity.
Apoptosis: Programmed cell death.
Immunoglobulins: Antibody proteins (IgG, IgM, IgA, IgE, IgD).
Cytokines: Signaling proteins that mediate immune responses.
Interferons: Proteins that inhibit viral replication and activate immune cells.
Chemokines: Cytokines that direct cell movement.
Primary immune response: First response to an antigen.
Secondary immune response: Faster, stronger response upon re-exposure to the same antigen.
Naturally acquired immunity: Immunity gained through natural exposure.
Artificially acquired immunity: Immunity gained through vaccination.
Passive immunity: Transfer of antibodies from another source.
Active immunity: Production of antibodies by the host's own immune system.

1. What are the five attributes of adaptive immunity? Specificity, diversity, memory, self-tolerance, and inducibility

2. What is the role of the lymphatic system in immunity? The lymphatic system is responsible for filtering pathogens and housing immune cells, facilitating the adaptive immune response.

3. Explain how a lymph node works? Lymph nodes filter lymph fluid and serve as a meeting point for immune cells to coordinate a targeted immune response.

4. One of the advantages of adaptive immunity over innate immunity is:

A. the response is targeted against a single pathogen.

B. the response is far faster.

C. the ability to recognize antigens common to many microbes.

D. the response targets classes of pathogen instead of specific pathogens.

E. a huge variety of cells are produced in response to an infection.

5. What is difference between an epitope and an antigen? An antigen is a molecule that can trigger an immune response, while an epitope is the specific part of the antigen that is recognized by immune cells (like antibodies or T-cell receptors). An antigen is typically a larger molecule, and it can have multiple epitopes.

6. Which of the following is an exogenous antigen? (you should learn about the other two antigen types also)

A. a bacterium inside a cell

B. a virus inside a cell

C. a bacterium outside a cell

D. a noninfected human cell

E. the malaria parasite inside a red blood cell

7. What are the names of the two kinds of white blood cells primarily responsible for adaptive immunity? B cells (B lymphocytes) and T cells (T lymphocytes).

8. Which of the following is TRUE of memory T cells?

A. They require many regulatory signals.

B. They persist for several months to years in lymphoid tissue.

C. They are not as effective as a primary response with a previously encountered antigen.

D. Both A and C are correct.

9. After an initial exposure to a pathogen, the phenomenon of _immunological memory (or adaptive immunity)__ produces a faster, more effective response to subsequent exposures.

10. What is the role of interleukins? Interleukins are a group of cytokines that play a crucial role in regulating immune and inflammatory responses.

11. The antibody immune response is attributed to the action of what type of cell? B cells (B lymphocytes)

12. The perforin-granzyme pathway involves:

A. the production of fever, which kills the pathogen

B. the production of antibodies toward the invading pathogen

C. the synthesis of special cell-killing proteins that act on infected or abnormal cells

D. presenting the foreign antigen to B cells

13. What are major histocompatibility antigens in general? Proteins

14. Explain the role of MHC I and MHC II. What information do they contain? What are they made of? What cell or cell parts bind/recognize what specific MHC? MHC class I molecules display fragments of proteins synthesized within the cell (e.g., normal self-proteins or foreign proteins from intracellular pathogens like viruses) to cytotoxic T cells. This signals if a cell is healthy or infected. MHC class II molecules display fragments of external proteins (antigens) that have been internalized and processed by specialized antigen-presenting cells (APCs) to helper T cells. This helps initiate a broader immune response.

15. Vaccination triggers an immune response which produces ________ immunity.

A. artificial passive

B. natural passive

C. natural active

D. artificial active

E. both active and passive

16. Where in the body does clonal deletion of developing T lymphocytes takes place? Thymus

17. What is the main function of B lymphocytes? Producing antibodies

18. Leukocytes migrate to a site of infection in response to what signal? Chemokines

19. What type of immunity is produced by the body when a person contracts a disease? Naturally acquired active immunity

20. Which of the following cytokines act as a signal between leukocytes?

A. growth factors

B. interferons

C. interleukins

D. tumor necrosis factors

E. chemokines

21. Which of the following statements concerning plasma cells is TRUE?

A. They live for many years and function as memory cells.

B. They are descended from activated T cells.

C. They can produce large quantities of antibodies on a daily basis.

D. They secrete a variety of antibody molecules specific for multiple epitopes.

E. The antibodies they produce can remain in circulation for years.

22. Antibodies are produced by cells called _plasma cells_.

23. Match the antibody class with its description.

___D___IgA A. This class of antibody is the only one that can cross the placenta.

___E___IgD B. This class of antibody is the first to appear after activation of B cells.

___C___IgE C. This class of antibody is involved in the defense against parasitic infections and involved in allergic responses.

___A___IgG D. This class of antibody is found in very large amounts in mucus secretions.

___B___IgM E. This class of antibody is not secreted by B cells but is expressed on the surface of naïve B cells.

24. ___Humoral___ immunity involves the production of antibody molecules that bind to specific antigens.

25. The heavy chains of an antibody molecule contain ___constant___ region segments, which help to determine its class or isotype.

26. The variable regions of the heavy and light chains form the ___antigen-binding___ sites of an antibody.

27. Explain how T and B cells interact with the T-dependent antibody immune response (Fig 16.18) In a T-dependent immune response, B cells internalize an antigen, process it, and present fragments on their surface via MHC class II molecules. A helper T cell (T sub H cell) that recognizes the same antigen fragment then binds to the B cell. This interaction, along with cytokines released by the

T sub H cell, activates the B cell, leading to its proliferation and differentiation into antibody-secreting plasma cells and memory B cells.

Adaptive Immune System Features

Specificity for particular antigens.
Memory for faster response upon re-exposure.
Involves B cells (humoral immunity) and T cells (cell-mediated immunity).

Antibody Structure

Composed of two heavy and two light chains.
Variable regions form antigen-binding sites.
Constant regions determine class (isotype).

Table: Classes of Immunoglobulins

Class	Main Function
IgG	Most abundant, crosses placenta, long-term immunity
IgM	First produced, pentamer, effective in agglutination
IgA	Found in mucous secretions
IgE	Involved in allergic responses and defense against parasites
IgD	Functions mainly as a B cell receptor

Antigen Presentation and MHC

MHC I: Present on all nucleated cells, presents endogenous antigens to cytotoxic T cells.
MHC II: Present on antigen-presenting cells, presents exogenous antigens to helper T cells.

Types of Immunity

Active immunity: Host produces own antibodies (natural infection or vaccination).
Passive immunity: Antibodies received from another source (maternal antibodies, antiserum).

Additional info:

Interleukins are cytokines that mediate communication between leukocytes.
Memory cells enable rapid secondary immune responses.
Apoptosis is essential for removing infected or abnormal cells.