Microbiology Final Exam Study Guide: Immunity, Immune Disorders, Vaccines, and Cardiovascular/Lymphatic Infections

Chapter 11: Innate Immunity

Overview of the Immune System and Responses

The immune system protects the body from pathogens through two main types of responses: innate and adaptive immunity. Understanding their differences is essential for recognizing how the body defends itself.

• Innate Immunity: The body's first line of defense, present from birth, providing rapid, non-specific responses to pathogens.

• Adaptive Immunity: Develops over time, is specific to particular pathogens, and involves memory for faster responses upon re-exposure.

• Normal Microbiota: The community of microorganisms living on and in the human body that can outcompete pathogens and modulate immune responses.

• Example: Lactobacillus species in the gut help prevent colonization by harmful bacteria.

First-Line Defenses: Mechanical, Chemical, and Physical Barriers

First-line defenses prevent pathogen entry through various barriers.

• Mechanical Barriers: Physical removal of microbes (e.g., cilia in the respiratory tract, flushing action of tears and urine).

• Chemical Barriers: Substances that destroy or inhibit microbes (e.g., stomach acid, lysozyme in saliva and tears, antimicrobial peptides [AMPs] in skin and mucosa).

• Physical Barriers: Structural features that block pathogen entry (e.g., intact skin, mucous membranes).

• AMPs: Antimicrobial peptides are found in various body sites and contribute to chemical defense (general concept only).

Second-Line Defenses and the Lymphatic System

When pathogens bypass first-line defenses, second-line defenses are activated, involving immune cells and the lymphatic system.

• Lymphatic System: A network of vessels and tissues that transports lymph and houses immune cells.

• Primary Lymphoid Tissues: Sites of immune cell production and maturation (e.g., bone marrow, thymus).

• Secondary Lymphoid Tissues: Sites where immune responses are initiated (e.g., lymph nodes, spleen).

• Leukocytes: White blood cells essential for immune responses.

Leukocytes of the Immune System

• Neutrophils: Most abundant, phagocytic, first responders to infection.

• Eosinophils: Combat parasitic infections and involved in allergic responses.

• Basophils: Release histamine, involved in inflammation and allergic reactions.

• Mast Cells: Similar to basophils, found in tissues, key in allergic responses.

• Monocytes: Differentiate into macrophages and dendritic cells, phagocytic.

• Dendritic Cells: Antigen-presenting cells that activate adaptive immunity.

• Lymphocytes: Include B cells, T cells, and natural killer (NK) cells; central to adaptive immunity.

Molecular Second-Line Defenses: Cytokines

• Cytokines: Small proteins released by cells that regulate immune responses, inflammation, and cell communication.

• Cytokine Storm: An excessive, uncontrolled release of cytokines that can cause severe inflammation and tissue damage.

Inflammation and Fever

• Fever: Elevated body temperature as a protective response to infection, mediated by pyrogens.

• Inflammation: A localized response to injury or infection, characterized by redness, heat, swelling, pain, and loss of function.

• Three Main Functions of Inflammation:

  1. Recruit immune cells to sites of infection or injury.

  2. Contain and eliminate pathogens.

  3. Initiate tissue repair.

• Cardinal Signs: Redness (rubor), heat (calor), swelling (tumor), pain (dolor), and sometimes loss of function.

• Unregulated Inflammation: Can lead to tissue damage and chronic disease.

Chapter 12: Adaptive Immunity

Humoral Response of Adaptive Immunity

Adaptive immunity involves specific responses to pathogens, with humoral immunity mediated by antibodies produced by B cells.

• Antibody Isotypes:

  • IgG: Most abundant in blood, crosses placenta, provides long-term immunity.

  • IgA: Found in mucosal areas and secretions (e.g., saliva, tears, breast milk).

  • IgM: First antibody produced in response to infection, effective at agglutination.

  • IgE: Involved in allergic reactions and defense against parasites.

  • IgD: Functions mainly as a B cell receptor.

Humoral Memory and Immunity Types

• Humoral Memory Cells: Long-lived B cells that respond rapidly upon re-exposure to the same antigen.

• Primary Exposure: First encounter with an antigen; IgM produced first, followed by IgG.

• Secondary Exposure: Faster and stronger response, mainly IgG due to memory cells.

• Types of Humoral Immunity:

  • Natural Active: Immunity from infection.

  • Natural Passive: Immunity from mother (e.g., IgG via placenta, IgA via breast milk).

  • Artificial Active: Immunity from vaccination.

  • Artificial Passive: Immunity from injection of antibodies (e.g., antiserum).

Chapter 13: Immune Disorders

Immunodeficiencies

• Primary Immunodeficiency: Congenital, genetic defects present at birth (e.g., SCID).

• Secondary Immunodeficiency: Acquired due to external factors (e.g., HIV infection, chemotherapy).

Autoimmune Disorders

• Definition: Conditions where the immune system attacks the body's own tissues.

• Examples: Type 1 diabetes, rheumatoid arthritis, lupus.

Hypersensitivity Reactions

• Definition: Excessive or inappropriate immune responses to antigens.

• Four Types of Hypersensitivity:

  1. Type I (Immediate): IgE-mediated, e.g., allergies, anaphylaxis.

  2. Type II (Cytotoxic): IgG/IgM-mediated, e.g., hemolytic anemia, transfusion reactions.

  3. Type III (Immune Complex): Immune complex deposition, e.g., serum sickness.

  4. Type IV (Delayed): T cell-mediated, e.g., contact dermatitis, TB skin test.

Anaphylaxis

• Definition: Severe, rapid allergic reaction that can be life-threatening.

• Localized Anaphylaxis: Limited to a specific area (e.g., hives, asthma).

• Systemic Anaphylaxis: Affects the whole body, can cause shock and requires immediate treatment.

• Signs and Symptoms: Swelling, difficulty breathing, low blood pressure, rash.

Blood Types and Transfusion Compatibility

• Blood Types: Determined by antigens on red blood cells (A, B, AB, O) and Rh factor (+/-).

• Compatibility: Incompatible transfusions can cause hemolytic reactions (Type II hypersensitivity).

Donor Blood Type	Recipient Blood Type	Compatible?
O-	All types	Yes (universal donor)
AB+	AB+	Yes (universal recipient)
A	A, AB	Yes
B	B, AB	Yes
O	O, A, B, AB	Yes
AB	AB	Yes
Additional info:	Rh factor must also be considered for compatibility.

Chapter 14: Vaccines

Purpose and Mechanism of Vaccination

• Purpose: To stimulate adaptive immunity and provide protection against specific diseases without causing illness.

• How Vaccines Work: Introduce antigens to the immune system, leading to the development of memory cells.

Herd Immunity

• Definition: When a high percentage of the population is immune, the spread of disease is limited, protecting those who are not immune.

• Natural vs. Artificial: Immunity can be acquired through infection (natural) or vaccination (artificial).

Types of Vaccines

• Live Attenuated Vaccines: Contain weakened forms of the pathogen; induce strong, long-lasting immunity but may not be suitable for immunocompromised individuals.

• Inactivated Vaccines: Contain killed pathogens or components; safer but may require booster doses.

Chapter 21: Cardiovascular and Lymphatic Infections

Anatomy & Physiology Overview

• Cardiovascular System: Composed of the heart, blood, and blood vessels; transports nutrients, gases, and immune cells.

• Lymphatic System: Network of lymph vessels and nodes; returns fluid to the bloodstream and houses immune cells.

• Connection: Lymphatic fluid drains into the cardiovascular system, facilitating immune surveillance and response.

Sepsis

• Definition: A life-threatening organ dysfunction caused by a dysregulated host response to infection.

• Signs and Symptoms: Fever, rapid heart rate, low blood pressure, confusion, organ failure.

• Complications: Septic shock, multi-organ failure, death.

Cardiovascular and Lymphatic Infections: Recognition and Terminology

• Transmission: Pathogens may enter via wounds, insect vectors, or medical procedures.

• Signs and Symptoms: Vary by disease; may include fever, lymphadenopathy, rash, or endocarditis.

• Pathogen/Etiology: Bacteria (e.g., Staphylococcus aureus), viruses, fungi, or parasites.

• Terminology: Endocarditis (infection of heart lining), lymphadenitis (lymph node infection), bacteremia (bacteria in blood).

Additional info:

• Students should review specific diseases, their transmission, and complications as covered in class materials and slides.

• Refer to visual summaries and tables in the textbook for further clarification.