Immune System and Pathogens Flashcards

Flashcards for reviewing lecture notes on the immune system, pathogens, and lines of defense.

Immune System

The body's defense system that allows us to resist infection by the millions of pathogens that we come in contact with everyday.

Antigen

Molecules that interact with the immune system; can be self or non-self.

Self-Antigen

Located on the surface of cells and mark the cells of an organism as 'self' so that the immune system doesn’t attack them. Often in the form of major histocompatibility complex (MHC) markers.

MHC Class I Markers

Self-antigens that are expressed on all nucleated cells (not RBCs) in the body.

MHC Class II Markers

Self-antigens that are found on specialised cells of the immune system.

Autoimmune Disease

A condition where the immune cells mistakenly recognise 'self' cells as non-self and attacks them.

Allergen

Antigens that cause the immune system to overreact; not pathogenic.

Pathogen

A disease causing agent that can be cellular or non-cellular.

Cellular Pathogens

Include parasites, protozoa, fungi and bacteria.

Non-cellular Pathogens

Include viruses and prions.

Bacteria

Prokaryotic (unicellular) organisms that reproduce via binary fission. Can be treated with antibiotics.

Fungi

Eukaryotic organisms with long, branching filaments called hyphae. Are treated with antifungal agents.

Parasites

An organism that obtains its nourishments from a host organism that it is found in or on which causes harm over time; Multicellular, eukaryotic invertebrate.

Protozoa

Unicellular eukaryotic organisms that reproduce via asexual and sexual reproduction. Some are carried by vectors.

Virus

Non-cellular pathogen with a core of nucleic acid (DNA or RNA) surrounded by a protein coat called a capsid. Unable to replicate outside of a host cell.

Prion

Abnormal and infectious misfolded proteins that change normal cell proteins into prions by direct contact.

Infectious Disease

Disease that can be passed from person to person caused by pathogens.

Non-Infectious Disease

Disease that cannot be passed from person to person caused by inherited, lifestyle associated, or nutritional factors

Virulence

The severity of disease a pathogen can cause

Carrier

An organism who shows no sign of the disease but who is host to a pathogen that may be transmitted to another.

Epidemic

Many people in an area become infected with a pathogen in a short amount of time.

Pandemic

World wide (or many countries) spread of a disease from its point of origin across a relatively short period of time (eg COVID-19)

Immune System First Line of Defense

Prevents entry of pathogens through physical, chemical, and microbiological barriers

Immune System Second Line of Defense

Destroys pathogens once they are in the system through innate immune responses

Immune System Third Line of Defense

Adaptive immune response that eliminates pathogens and creates memory cells

Innate Immunity

Non-specific immunity that responds the same to repeated infections, has no memory, includes plants first line of defense and animals first and second lines of defense.

Adaptive Immunity

Specific immunity acquired through contact with pathogens, induces tolerance to self-antigens, generates immunological memory, includes animals third line of defense.

Plant Physical Barriers

Cell walls, waxy cuticle, bark, thorns, and spines that prevent pathogen entry or herbivore attack.

Plant Chemical Barriers

Include toxins such as alkaloids produce an odour via volatile oils (mint, sage) or a repellent taste to protect against fungal, bacterial or herbivore attack. Other toxins directly act on other organisms and can cause death, lethargy (opioids), stimulation (caffeine), irritation (capsaicin) and neurotoxins (pyrethrins).

Animal First Line of Defense Barriers

Intact skin, cillia, mucous, secretions / expulsions, acid, enzymes, sweat, and natural flora that prevent pathogen entry.

Phagocytes

White blood cells (leukocytes) that engulf (via endocytosis) and destroy invading microorganisms.

Antigen-Presenting-Cells

Macrophages and Dendritic cells are known as Antigen-Presenting-Cells.

Natural Killer Cells

Cells used for immunological surveillance that recognise unusual proteins on the surfaces of virally infected and cancerous cells. Can induce apoptosis.

Mast Cells

Reside in connective tissues and degranulate, releasing histamine upon stimulation, resulting in inflammation.

Eosinophils

Contain toxic chemical mediators, such as proteases, that help destroy pathogens which are too large to be phagocytosed.

Interferons

Cytokines manufactured and released by cells when they get infected by viruses or are cancerous cells that protect against viral infections by interfereing with viral replication.

Complement Proteins

Proteins found in the blood that are activated by the presence of pathogens

Inflammation

A short term (acute) localised response to a pathogen (or damage) which results in the affected tissue becoming red, swollen, hot, and often painful.

B Lymphocytes

The key mediators of humoral immunity activated throught interaction with pathogenic antigens and T helper cells.

T Lymphocytes

Key mediators of cell-mediated immunity, including T helper cells and cytotoxic T cells.

Antibodies

Specific protein structures (immunoglobulins) that specifically recognise antigens, neutralise the infectivity of microbes and target them for elimination

Cytotoxic T Cells

Cells with T cell receptor that are specific to the foreign antigen they were selected for- bind to an abnormal cell that is presenting complementary foreign antigens on its MHC I complex to induce apoptosis.

Primary Lymphoid Tissues

Include Bone marrow and Thymus for Production of immature B and T cells, and Maturation of T cells.

Secondary Lymphoid Tissues

Include Lymph nodes and Spleen for Site where APCs meet lymphocytes and initiation of the adaptive immune response

Neutralization (Antibody Function)

Antibodies block the sites of pathogens that are used to attack host cells and can block the active sites of toxins.

Agglutination (Antibody Function)

Antibodies bind together with antigens on two separate pathogens, forming large antigen-antibody complexes, easier for phagocytes to recognise.

Immobilization (Antibody Function)

Antibodies restrict the movement of pathogens around the body through the formation of large antigen-antibody complexes

Opsonization (Antibody Function)

Antibodies bind directly to the surface “flagging” of a pathogen to make it easier to phagocytose

Activation of Complement Proteins (Antibody Function)

Formation of membrane attack complexes (MACs)