Dealing with Disease: Pathogens and Immunology

Vocabulary flashcards covering cellular and non-cellular pathogens, the innate and adaptive immune systems, and the structures of the lymphatic system based on lecture notes.

Pathogen

Any agent that causes disease, which can be cellular (living) or non-cellular (non-living).

Endemic

A disease condition that is common in a population but remains at a low level.

Outbreak

A sudden increase in the incidence of a disease within a specific population of a species.

Pandemic

An outbreak of disease that spreads rapidly across the world.

Prion

A non-cellular pathogen composed only of protein, without genetic material, characterized by being incorrectly folded.

Bacteria

Unicellular prokaryotes that reproduce rapidly, typically every $20-30$ minutes, and can release harmful chemicals called toxins.

Protozoa

Unicellular eukaryotes that cause sickness because they are parasites; examples include Plasmodium and Giardia lamblia.

Incubation Period

The period after infection and before the first symptoms appear, during which the infectious agent is multiplying.

Asymptomatic

A state where an individual is infected by a pathogen but never shows any signs or symptoms of the disease while still being infectious to others.

Antigen

A substance recognized by the immune system that can be identified as either self or non-self (foreign).

$MHC\ I$ markers

Major histocompatibility complex proteins expressed on all human cells except red blood cells that serve as self-markers.

$MHC\ II$ markers

Proteins expressed on certain immune system cells, specifically antigen-presenting cells (APCs), to initiate immune responses.

Allergens

Antigens that the body mistakenly identifies as pathogens, resulting in a strong immune response known as an allergic reaction.

Innate Immunity

The non-specific, rapid first and second lines of defense that are present from birth and do not provide long-lasting memory.

Adaptive Immunity

The specific third line of defense that involves a slower response but provides immunological memory.

Phagocytosis

The process by which cellular components like neutrophils, macrophages, and dendritic cells engulf and destroy foreign or dead material.

Natural Killer (NK) cells

Innate immune cells that recognize and destroy infected or abnormal body cells by releasing cytotoxic chemicals like granenzymes and perforin.

Mast cells

Cells that respond to injury or allergens by releasing histamines, which are critical for the inflammatory response.

Eosinophils

Large granulated cells that secrete toxic chemical mediators to destroy invading pathogens too large to be engulfed, such as parasites.

Interferons

Cytokines released by virally-infected cells that signal neighboring cells to change their properties to become less susceptible to infection.

Complement system

A group of over $30$ blood proteins that aid in opsonisation, attract phagocytes, and form membrane attack complexes (MAC) to destroy bacteria.

Inflammatory response

A process involving initiation, vasodilation, and migration that increases blood flow to an injury site, causing swelling, heat, and redness.

Humoral immune response

The adaptive immune pathway that responds to extracellular pathogens and involves B cells and the production of antibodies.

Cell-mediated immune response

The adaptive immune pathway that responds to intracellular pathogens and involves cytotoxic $T$ cells ($T_{c}$).

B Lymphocytes

White blood cells that, when selected, differentiate into plasma cells that secrete antibodies or long-living memory B cells.

Plasma cells

Effector B cells that secrete antibodies into the bloodstream at a rate of approximately $2000$ molecules per second.

Antibodies

Y-shaped proteins, also known as immunoglobulins (Ig), that are complementary to specific foreign antigens.

Cytotoxic $T$ cells ($T_{c}$)

Lymphocytes that destroy target cells by recognizing specific antigens and inducing apoptosis via death ligands like FasL.

Helper $T$ cells ($T_{h}$)

Cells that secrete cytokines like interleukins to stimulate the proliferation of activated B and $T$ lymphocytes.

Clonal Selection

The process by which a single lymphocyte that recognizes a specific pathogen is selected from millions to proliferate and differentiate.

Lymph Nodes

Small bean-shaped secondary lymphoid organs that filter lymph and serve as sites where lymphocytes meet their matching antigens.

Thymus

A primary lymphoid organ located behind the sternum which serves as the site for the development of mature $T$ lymphocytes.

Bone Marrow

Primary lymphoid tissue in the center of long bones where all immune cells originate and where B cells mature.

Agglutination

The process by which antibodies bind to pathogens and cause them to clump together, facilitating easier removal by phagocytes.

Opsonisation

The coating of a pathogen with complement proteins or antibodies to signal to phagocytes that they are foreign material.

HLA system

The Human Leukocyte Antigen system, which is a gene complex encoding the major histocompatibility complex (MHC) proteins in humans.