Immunology Chapter 5 Quiz

Chapter 9: Immunity

• This chapter covers the topic of immunity.

• Various pathogens are mentioned, including viruses (flu, common cold, chicken pox, HIV/AIDS, COVID-19), bacteria (tuberculosis, salmonella, cholera, urinary tract infections, gonorrhea), protists (malaria, amoebic dysentery), fungi (athlete's foot, yeast infection), and animals (intestinal fluke, whipworm).

• Physical and chemical barriers act as the first line of defense, preventing pathogens from entering the body. Examples of these include skin (epidermis), tears, saliva, mucus (containing lysozymes), earwax, digestive acids, vaginal acids, urine, vomiting, and defecation/diarrhea.

• Innate immunity (second line of defense) is a nonspecific defense mechanism that attacks pathogens that enter the body without recognizing specific pathogens.

• Adaptive immunity (third line of defense) is a specific immune response that recognizes specific pathogens the body has encountered before.

Innate Immunity: Types of White Blood Cells

• Neutrophils (2/3 of WBC's): These are attracted to infected/damaged tissue, leave capillaries, engulf (phagocytize) bacteria, and digest them with lysosomes. Dead neutrophils form pus.

• Macrophages: Develop from monocytes, leave capillaries, engulf bacteria, dead cells, and dead neutrophils; release cytokine chemicals (pyrogens) causing fever. Also function as antigen-presenting cells.

• Eosinophils: Attack large parasites (like worms) by surrounding them and releasing digestive enzymes.

• Natural Killer Cells: Recognize and kill infected (viruses) or cancerous cells.

• Complement Proteins: Present in blood and tissue fluids. Activated complement proteins attach to pathogens, attract neutrophils and macrophages to destroy them, and help them engulf pathogens. They "punch holes" in bacterial membranes, causing water influx and cell rupture (osmosis).

• Inflammatory Response: Mast cells and basophils in connective tissue release histamine, causing inflammation. Signs include redness, warmth, swelling (edema), and pain. Histamine dilates arterioles, increasing blood flow to the site and bringing in immune cells. Increased permeability of capillaries allows nutrients and immune cells to reach affected tissue

• Fever: Raising body temperature (up to 39°C) can be useful as it creates an unfavorable environment for bacteria and increases activity of white blood cells and tissue repair. High sustained fevers can be dangerous, impacting proteins.

Adaptive Immunity: Lymphocytes

• B Lymphocytes: Produce antibodies that bind to foreign antigens (surface proteins of viruses, bacteria, etc.) Millions of different types.

• Cytotoxic T Lymphocytes: Kill foreign cells, virus-infected cells, and cancerous cells.

• Helper T Lymphocytes: Coordinate the immune response by causing the cell division of cytotoxic T cells and B lymphocytes. They are vitally important, since HIV infects helper T cells.

Adaptive Immunity: Key Features

• Targets specific antigens (proteins).
• High diversity of B and T lymphocytes. B and T cells recognize specific antigens that enter the body.
• Produces memory B and T cells during initial exposure to an antigen. These cells remain in the body to mount a quick, potent secondary response upon re-exposure.

Adaptive Immunity: B Cells and Antibodies

• Each B lymphocyte produces one unique antibody.
• Antibodies bind to specific antigens. If an antibody encounters a matching antigen, the B cell rapidly multiplies, creating effector B cells and memory cells, both producing the same antibody.
• Effector B cells secrete antibodies into lymph and blood to bind to pathogens with identical antigens.
• Memory B cells remain in the body for future, faster response.

Adaptive Immunity: T Cells

• Each helper T lymphocyte and cytotoxic T lymphocyte produce one unique protein receptor.
• Various types, each targeting a specific antigen.

Adaptive Immunity: Cytotoxic T Cells

• Macrophages engulf pathogens and present antigens to T cells (helper T and cytotoxic T).
• If a cytotoxic T cell's receptor matches a presented antigen, it divides, producing copies of itself.
• Some copies become effector cytotoxic T cells that kill cells with that antigen. Others become memory cells for future attacks.

Adaptive Immunity: Helper T Cells

• Helper T cells stimulate other immune cells (macrophages, cytotoxic T cells, and B lymphocytes)
• Critical for initiating the rapid division of effector B cells and cytotoxic T cells.
• Without helper T cells, immune response is significantly hampered.
• Memory cytotoxic T and helper T cells remain, enabling a faster response to future attacks by similar pathogens.

1st Exposure to a Pathogen

• Significant lag time (3-6 days) between pathogen entry and antibody production.
• Individual will typically experience sickness during the initial response.
• Antibody concentration peak at 10-12 days.
• Formation of memory B and T cells.

2nd Exposure to a Pathogen

• Much quicker (hours) lag time and overwhelming response.
• High antibody response rate. Infection is often prevented from causing sickness.

Comparing Primary and Secondary Responses

• Secondary response (re-exposure) is much faster and produces greater antibody production than the primary response.

Flu/Cold Recurrence

• Flu virus mutations lead to new antigens, rendering pre-existing memory cells ineffective.
• Common colds are caused by numerous viruses. Consequently, exposure to one virus doesn't confer immunity to others.

Lymphatic System

• Picks up bacteria and pathogens, transporting them to lymph nodes.
• Lymph nodes contain macrophages and lymphocytes, producing effector B cells, cytotoxic T cells, helper T cells, and memory T and B cells.
• Lymph vessels and nodes connect with the blood system. These systems thus facilitate antibody and cell dispersal.
• Lymphatic system structure involves blind-ended capillaries with larger intercellular gaps for bacterial uptake, one-way valves, and lymph, containing plasma fluid, WBC's, fats etc.

Early Childhood Immunity/Breastfeeding

• Antibodies pass across the placenta.
• Antibodies, phagocytes, and lymphocytes are present in breast milk, providing initial immunity to the child
• Breast milk provides necessary nutrients that babies need in their first weeks

Active Immunization (Vaccination)

• Exposure to weakened pathogens triggers memory B and T cell formation, enabling immunity without the illness.
• Vaccines can eradicate diseases or reduce incidence rates.
• mRNA vaccines produce the antigen; the body creates memory cells for future exposure.
• Vaccines against virus mutations are continuously required.

Passive Immunization

• Injecting pre-made antibodies to fight existing infections.
• Short-term immunity for the recipient due to lack of memory cell production.

Antibiotics

• Effective only against bacteria, not viruses.
• Antibiotic resistance is a growing concern.

Donating Organs/Tissue Rejection

• Transplanted organs have foreign antigens that elicit an immune response.
• Matching blood types or antigens and immunosuppressive drugs can reduce rejection.
• Effective techniques, combined with increased donor supply, are necessary for transplantation success.

Allergies

• Harmless substances trigger an immune response, causing histamine release, inflammation, redness, swelling, pain, and mucus production.
• Allergies can be localized or cause anaphylactic shock, a potentially fatal, full-body response.

Autoimmune Diseases

• Defective "self" recognition leads to the immune system attacking the body's own cells.
• Examples include multiple sclerosis (impacting central nervous system (CNS)); type 1 diabetes (affecting pancreas insulin production); and rheumatoid arthritis (affecting synovial joints).

Test your knowledge on the immune system and its functions with this quiz focused on Chapter 5 of immunology. Explore topics such as the roles of various immune cells, the importance of physical barriers, and the intricacies of pathogen recognition. Challenge yourself and see how much you know about innate and adaptive immunity.