Immune System Disorders, Vaccines, Antimicrobial Drugs, and Infectious Diseases: Study Guide

Chapter 13: Immune System Disorders

Overview of Immune System Disorders

Immune system disorders encompass a range of conditions where the immune response is abnormal, including deficiencies, hypersensitivities, and autoimmunity. Understanding these disorders is crucial for diagnosing and treating immune-related diseases.

• Immunodeficiency: A state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Can be primary (genetic) or secondary (acquired).

• Autoimmunity: The immune system mistakenly attacks the body's own tissues, leading to autoimmune diseases.

• Autoantibodies: Antibodies produced against self-antigens, often seen in autoimmune diseases.

• Hypersensitivity: Excessive or inappropriate immune responses to antigens, classified into four types (I-IV).

• Allergen: A normally harmless substance that triggers an allergic response in susceptible individuals.

• Allergy: A hypersensitivity reaction to environmental antigens (allergens).

• Atopic asthma: Asthma triggered by allergens, characterized by airway inflammation and bronchoconstriction.

• Angioedema: Rapid swelling of the dermis, subcutaneous tissue, mucosa, and submucosal tissues, often due to allergic reactions.

• Sensitizing exposure: The initial exposure to an allergen that primes the immune system for future reactions.

• Desensitization: A therapeutic process to reduce allergic responses by repeated exposure to increasing amounts of allergen.

• Localized anaphylaxis: Allergic reactions confined to a specific area, such as hay fever or asthma.

• Systemic anaphylaxis: A severe, potentially life-threatening allergic reaction affecting the whole body.

• Cytotoxic reactions (or cytolytic reactions): Immune responses that result in the destruction of cells, often involving antibodies and complement.

• Hemolytic transfusion reaction: Destruction of red blood cells following transfusion of incompatible blood.

• Autoimmune hemolytic anemia: The immune system destroys the body's own red blood cells.

• Serum sickness: A reaction to proteins in antiserum derived from a non-human animal source.

• Contact dermatitis: Inflammation of the skin caused by direct contact with an allergen or irritant.

Types of Hypersensitivity Reactions (ACID Acronym)

• Type I (A) – Immediate (Allergic/Anaphylactic): IgE-mediated, rapid onset (e.g., hay fever, asthma, anaphylaxis).

• Type II (C) – Cytotoxic: IgG or IgM antibodies target cells, leading to cell destruction (e.g., hemolytic anemia, transfusion reactions).

• Type III (I) – Immune Complex: Immune complexes deposit in tissues, causing inflammation (e.g., serum sickness, systemic lupus erythematosus).

• Type IV (D) – Delayed (Cell-mediated): T-cell mediated, delayed response (e.g., contact dermatitis, tuberculosis skin test).

Key Concepts and Practice Questions

• Compare and contrast primary vs. secondary immunodeficiencies.

• Discuss why cancer can be considered a failure of the immune system.

• Define the term "autoimmune disorder" and provide examples (e.g., Type 1 diabetes, rheumatoid arthritis).

• Describe the four types of hypersensitivity reactions using the ACID acronym.

• Explain the role of allergens and the mechanism of allergic responses.

• Describe the clinical features and treatment of hemolytic disease of the newborn (HDN).

• Discuss the development and treatment of serum sickness.

• Explain the differences between autografts, isografts, allografts, and xenografts in transplantation immunology.

• Describe graft-versus-host disease (GVHD) and its clinical significance.

Chapter 14: Vaccines and Biotechnology-Based Diagnostics and Therapeutics

Overview of Vaccines and Immunization

Vaccines are biological preparations that provide immunity to specific infectious diseases. Modern biotechnology has expanded vaccine development and diagnostic tools.

• Herd immunity: Protection of unvaccinated individuals in a population when a sufficient proportion is immune.

• Live attenuated vaccines: Contain weakened forms of the pathogen that induce strong, long-lasting immunity (e.g., MMR vaccine).

• Inactivated vaccines: Contain killed pathogens; safer but may require boosters (e.g., polio vaccine).

• Whole-agent vaccines: Use entire pathogens, either inactivated or attenuated.

• Subunit vaccines: Contain only parts of the pathogen (e.g., proteins, polysaccharides).

• Adjuvant: Substance added to vaccines to enhance the immune response.

• Nucleic Acid (DNA and RNA) vaccines: Use genetic material to induce immunity (e.g., mRNA COVID-19 vaccines).

Biotechnology-Based Diagnostics

• Enzyme-linked immunosorbent assay (ELISA): Detects antigens or antibodies using enzyme-linked antibodies and color change.

• Polymerase chain reaction (PCR): Amplifies DNA sequences for detection of pathogens.

• Reverse transcription PCR (RT-PCR): Converts RNA to DNA before amplification, useful for RNA viruses.

• Recombinant DNA: DNA molecules formed by laboratory methods to bring together genetic material from multiple sources.

Key Concepts and Practice Questions

• Review the history of vaccines from variolation to modern advancements.

• Discuss the principles of immunity underlying vaccination.

• Explain herd immunity and its importance in public health.

• Compare and contrast types of vaccine formulations (live-attenuated, inactivated, subunit, etc.).

• Describe the purpose of adjuvants in vaccines.

• Discuss the process and applications of gene therapy using viral vectors.

• Describe and interpret ELISA and PCR techniques.

Chapter 15: Antimicrobial Drugs

Overview of Antimicrobial Drugs

Antimicrobial drugs are agents used to treat infections by killing or inhibiting the growth of microorganisms. They include antibiotics, antivirals, antifungals, and antiparasitics.

• Antimicrobial drugs: Compounds that kill or inhibit the growth of microorganisms.

• Antibacterial/Antiviral/Antiparasitic/Antifungal drugs: Drugs targeting specific types of pathogens.

• Antibiotics: Substances produced by microorganisms that inhibit or kill other microbes.

• Selective toxicity: The ability of a drug to target pathogens without harming the host.

• Therapeutic index: Ratio of toxic dose to therapeutic dose; higher values indicate safer drugs.

• Resistance: The ability of microbes to withstand the effects of drugs that once killed them.

• Multidrug-resistant (MDR): Microbes resistant to multiple antimicrobial agents.

• Carbapenem-resistant Enterobacteriaceae (CRE): A group of bacteria resistant to carbapenem antibiotics, posing significant treatment challenges.

Modes of Action and Examples

Antimicrobials can be classified by their mode of action and spectrum of activity.

Drug	Mode of Action	Example Pathogen Treated
Penicillins	Inhibit cell wall synthesis	Streptococcus
Tetracyclines	Inhibit protein synthesis (30S ribosome)	Chlamydia
Macrolides	Inhibit protein synthesis (50S ribosome)	Mycoplasma
Fluoroquinolones	Inhibit DNA gyrase	Escherichia coli
Sulfa drugs	Inhibit folic acid synthesis	Streptococcus
Polymyxins	Disrupt cell membrane	Pseudomonas

Key Concepts and Practice Questions

• Explain the discovery of penicillin by Alexander Fleming and the genus Penicillium.

• Define broad vs. narrow spectrum antibiotics and their clinical implications.

• Compare bacteriostatic vs. bactericidal drugs.

• Discuss the development of drug resistance and strategies to combat it.

• Describe susceptibility testing (e.g., Kirby-Bauer test), zone of inhibition, and MIC/MBC determination.

• List the top three urgent drug-resistant bacterial threats in the United States.

Disease Survey

Overview of Selected Infectious Diseases

For each disease, know the causative agent, symptoms, signs, and transmission routes.

Disease	Causative Agent	Transmission
Smallpox	Variola virus	Respiratory droplets, fomites
HIV	Human immunodeficiency virus	Blood, sexual contact, vertical
Poliomyelitis	Poliovirus	Fecal-oral
Impetigo	Staphylococcus aureus, Streptococcus pyogenes	Direct contact
C. diff infection	Clostridioides difficile	Fecal-oral
Tuberculosis	Mycobacterium tuberculosis	Airborne droplets
Leprosy	Mycobacterium leprae	Prolonged close contact
Pneumococcal pneumonia	Streptococcus pneumoniae	Respiratory droplets
Strep throat	Streptococcus pyogenes	Respiratory droplets
Cholera	Vibrio cholerae	Fecal-oral (contaminated water)
Bubonic plague	Yersinia pestis	Flea bites, respiratory droplets
Tapeworm	Taenia spp.	Ingestion of larvae in undercooked meat
Syphilis	Treponema pallidum	Sexual contact
Typhoid fever	Salmonella typhi	Fecal-oral
Malaria	Plasmodium spp.	Anopheles mosquito bite
Giardia	Giardia lamblia	Fecal-oral
Ringworm	Dermatophyte fungi	Direct contact, fomites
Yeast infection	Candida albicans	Endogenous, overgrowth
Hookworm	Necator americanus, Ancylostoma duodenale	Penetration of skin by larvae

Additional info: For each disease, also review clinical presentation and prevention strategies as part of exam preparation.