IMMUNE SYSTEM

Lymphatic System

Removes excess fluid from tissues, absorbs fats, and protects against invaders.

Bone Marrow

Primary lymphoid organ where most immune cells are made.

Thymus

Primary lymphoid organ where T cells mature.

Lymph Nodes

Secondary lymphoid organs that filter and store immune cells.

Spleen

Secondary lymphoid organ that stores immune cells.

Tonsils

Secondary lymphoid organs that trap pathogens from the mouth and nasal cavity.

Appendix

Contains lymphoid tissue and is considered a secondary lymphoid organ.

Infectious Disease

Caused by pathogens and can be spread from person to person.

Noninfectious Disease

Not caused by pathogens, cannot be spread, often due to genetics or lifestyle.

Examples of Noninfectious Diseases

Cancer, diabetes, cardiovascular disease, chronic respiratory disease.

Bacteria

Prokaryotic single-celled organisms that produce toxins and can be treated with antibiotics.

Fungi

Eukaryotic organisms that can be single-celled or multicellular and cause disease by spore inhalation.

Viruses

Non-living pathogens that reproduce only in host cells and can be treated with antivirals.

Influenza A Virus

changes yearly due to genetic reassortment.

Influenza Infection Process

Virus enters cell, uses host machinery to replicate and assembles new viruses.

Vaccines

Prevention method for influenza due to antigenic variation.

Antibiotic Resistance

Occurs when bacteria mutate and survive antibiotic use, leading to superbugs.

First Line of Defence: Physical Barriers

Includes skin, cilia, and mucous that prevent pathogen entry.

First Line of Defence: Chemical Barriers

Includes stomach acid, urine, and secretions that kill or flush out pathogens.

First Line of Defence: Expulsion

Coughing, sneezing, vomiting, and diarrhoea that help remove pathogens.

Second Line of Defence

Activated if the first line fails, the second line will try remove anything that doesn’t have a MHC

Phagocytes

White blood cells, such as macrophages, that engulf and digest pathogens.

Natural Killer (NK) Cells

Destroy cells without MHC markers, such as virus-infected and cancer cells.

Cytokines

Chemical messengers that attract immune cells and interfere with viral replication.

Chemokines

Control the movement of immune cells and their release from bone marrow.

Fever

Raises body temperature to inhibit pathogen survival and activate immune cells.

Antigen

A substance that triggers an immune response and leads to antibody production.

MHC (Major Histocompatibility Complex)

Cell surface marker used to present antigens and identify self vs non-self.

Humoral Response

Involves B cells and antibodies, targeting extracellular pathogens.

B Cell Activation: Step 1

activation of a specific B cell (antigen)

B Cell Activation: Step 2

APC activates a T helper cell

B Cell Activation: Step 3

B cells and T helper cell meet, causing clonal expansion

B Cell Activation: Step 4

cells become either plasma cells that create antibodies or B memory cells

Plasma Cells

Produce and secrete antibodies to neutralize or destroy antigens.

Memory B Cells

Remain long-term and respond faster upon re-exposure.

Antibody Roles

Bind and neutralize pathogens, mark them for phagocytosis, or activate the complement system.

Cell-Mediated Response

Involves T cells targeting viral infected cells. Intracellular

T Cell Activation: Step 1

specific T cell is activated by the antigen

T Cell Activation: Step 2

APC activates a T helper cell

T Cell Activation: Step 3

T cell and T helper cell meet, causing clonal expansion

T Cell Activation: Step 4

some of the T cells become activated, killing viral cells. The other become T memory cells for long term memory

Vaccination: How It Works

Injects weakened or dead pathogen to trigger antibody and memory cell production.

Types of Vaccines

Including live attenuated, inactivated, and subunit vaccines.

Memory B Cells in Vaccines

Enable faster and larger antibody responses upon re-exposure.

Natural Active Immunity

Body produces antibodies after encountering a pathogen naturally.

Natural Passive Immunity

Antibodies received from mother through placenta or breast milk.

Artificial Active Immunity

Vaccination leads to body making antibodies and memory cells.

Artificial Passive Immunity

Injected antibodies provide immediate protection.

Herd Immunity

Large portion of the population is immune, protecting non-immune individuals.

Consequence-Based Ethics

Focuses on maximizing positive outcomes and minimizing harm.

Duty-Based Ethics

Follows rules and duties regardless of negative consequences.

Virtue-Based Ethics

Prioritizes moral character over outcomes or rules.

Inflammation

delivery of phagocytes (WBCs)

Pathogen

an organism or agent that causes disease

Adaptive Response

antigen specific, has memory

Innate immune response

1st and 2nd lines of defence (non-specific)

Vaccine boosters

creates more memory cells and gives better protection.

Third line of defence

searches for antigens and removes it

Antibodies

‘‘Y’ shaped structures that attach to antigens

B cell

a type of white blood cell that produces antibodies