Infectious Disease and Human Immunity

Flashcards covering the classification of pathogens, historical theories of disease, plant and animal immune responses, and strategies for controlling infectious diseases.

Pathogen

Biological agents that cause disease or illness in a host organism by releasing toxins, damaging tissue, or depriving normal cells of nutrients.

Viruses

Microscopic non-cellular pathogens containing DNA, RNA, and a protein coat; they require a living host cell to replicate.

Prions

Microscopic non-cellular pathogens that do not contain DNA or RNA and primarily attack brain or nerve cells.

Bacteria

Microscopic prokaryotic cells that cause disease by dividing quickly and/or producing toxins.

Fungi

Microscopic or macroscopic eukaryotic cells with a cell wall that spread via spores; an example is Phytophthora cinnamomi which causes dieback.

Protozoa

Microscopic single-celled eukaryotic organisms, such as Plasmodium which causes Malaria.

Epidemic

A disease that affects a large number of people within a population.

Pandemic

An epidemic that spreads over multiple countries or continents.

Endemic

A disease or condition that belongs to or is confined to a particular group or country.

Outbreak

An increase in the number of endemic cases that is larger than anticipated.

Direct Contact

Transmission via physical contact between a host and a non-infected organism, such as touching, sexual contact, or contact with bodily fluids.

Indirect Contact

Transmission with no physical contact, such as airborne droplets (sneezing/coughing) or contaminated food and water.

Vector Transmission

A form of indirect transmission where the pathogen is carried by organisms like mosquitoes, flies, ticks, or fleas.

Spontaneous Generation

The theory that life can arise from non-living material; this was disproved by Louis Pasteur's swan neck flask experiment.

Biogenesis

The principle that life comes from other life.

Germ Theory

The theory that infectious diseases are caused by the growth and spread of microorganisms called germs.

Koch's Postulates

A set of four criteria (Common, Culture, Cause, Compare) used to identify the causative organism for infectious diseases.

Apoptosis

Programmed cell death used to limit the spread of infection.

PAMPs

Pathogen Associated Molecular Patterns; structures found on pathogens that trigger immune responses in host cells.

Hypersensitive response (HR)

A localized plant response where cells produce oxidative agents to trap pathogens, which then die during apoptosis.

Systemic acquired resistance (SAR)

A non-specific, whole-plant response triggered by salicylic acid providing long-lasting protection against pathogens.

Microflora

Non-pathogenic microbes with a symbiotic relationship with the body that help prevent infection by outcompeting pathogens.

Phagocytosis

The process where leukocytes like neutrophils and macrophages engulf and break down pathogens using lysozymes.

Inflammatory response

A reaction triggered by histamines and prostaglandins that increases blood flow and capillary permeability at the site of infection.

Complement system

A group of proteins that can mark pathogens for phagocytosis (opsonization), attract macrophages (chemotaxis), or cause cell lysis.

Interferons

Cytokines released by virus-infected cells that signal uninfected cells to reduce protein synthesis and hinder viral replication.

Natural killer cells

Immune cells that patrol the body and distinguish between healthy and infected cells via the MHC I receptor to trigger apoptosis.

Antigens

Molecules recognized by the body as foreign that trigger an immune response.

Antibodies

Proteins called immunoglobulins produced by plasma cells that bind to specific antigens to deactivate or clump them.

Helper T-cells

Lymphocytes that release interleukin-2 to activate cytotoxic T-cells and B-cells specific to an antigen.

Cytotoxic T-cells

Activated T-cells that bind with infected cells and release chemicals to destroy them.

Plasma B-cells

B-cells that clone themselves to secrete antibodies into the blood and lymph.

Memory Cells

T and B lymphocytes that remain in the body after initial exposure to provide a faster response if the antigen is encountered again.

Active immunity

Immunity developed when the host's own adaptive immune system is activated to produce antibodies and memory cells.

Passive immunity

Short-term immunity acquired by receiving antibodies from an external source, such as maternal antibodies or monoclonal antibodies.

Incidence

The number of new cases of a disease in a population over a specific time, calculated as $\text{Incidence} = \frac{\text{no. new cases}}{\text{size of population}} \times 100$.

Prevalence

The total number of disease cases in a population at a given time, calculated as $\text{Prevalence} = \frac{\text{total cases}}{\text{population size}} \times 100$.

Antivirals

Drugs that inhibit the development of viruses inside infected cells but do not kill the viruses.

Antibiotics

Drugs used to treat bacterial infections by inhibiting protein synthesis, cell wall synthesis, or DNA replication.

Bush medicine

Traditional Aboriginal use of natural remedies, such as Eucalyptus oil for its antimicrobial properties or Tea tree oil as an antiseptic.

Smoke bush

A plant found in Western Australia containing conocurovone, which is used for healing and has potential against HIV/AIDS.