C3.2 Defence against disease Interaction and interdependence

Vocabulary flashcards covering the mechanisms of defense against disease, the immune system, blood clotting, lymphocytes, and immunology concepts from the C3.2 lecture notes.

Pathogen

A disease-causing organism, typically referring to viruses, bacteria, fungi, and protists.

CRANS

The shared characteristics of all pathogens: ability to colonize the host; use host resources to replicate; circumvent, avoid, or subvert the host’s immune responses; find a niche that is nutritionally compatible in the host; and spread to a new host.

Archaea

A domain of unicellular organisms that are not known to cause any disease in humans, likely because humans lack compatible nutritional sources for them.

John Snow

Considered the founding father of epidemiology, he observed cholera incidence in 19th-century London and used preventive measures like blocking access to contaminated water pumps.

Ignaz Semmelweis

A Hungarian physician who observed higher childbed fever fatalities among physicians examining cadavers and suggested using chlorinated lime as a disinfectant to reduce death rates.

Innate immune system

The first and second lines of defence that respond to broad categories of pathogens (non-specific) and do not change during an organism’s life.

Adaptive immune system

The third line of defence that responds specifically to particular pathogens and builds up a memory to make subsequent immune responses more effective.

TACID

Reasons why skin and mucous membranes act as primary defence: tears and mucous trap pathogens; skin acidity; competition with normal flora; continuous impermeable barrier; and deactivating pathogens by desiccation.

Thrombin

An active enzyme converted from inactive prothrombin that facilitates the conversion of soluble fibrinogen into insoluble fibrin during blood clotting.

Fibrin

An insoluble protein that forms a mesh around a skin injury site, trapping erythrocytes to form a blood cloth.

Phagocyte (Macrophage)

A type of white blood cell (leukocyte) that recognizes pathogens, engulfs them by endocytosis, and digests them using enzymes from lysosomes.

Amoeboid movement

The specific type of movement characterizing phagocytes that allows them to move through small pores in capillaries to reach sites of infection.

Lymphocytes

Cells of the adaptive immune system, numbering around $2 \times 10^{12}$ in the human body, that circulate in blood and lymph nodes.

B-lymphocytes

Lymphocytes produced in the bone marrow that each produce a specific type of antibody (immunoglobin).

T-lymphocytes

Lymphocytes produced in the thymus that are part of the adaptive immune system.

Variable region

The part of an antibody that determines its specificity, similar to the shape of an enzyme's active site.

Complement activation

A mechanism of antibody defense involving proteins that work to fight off disease by opsonization and cell lysis.

Opsonization

The process where an antibody binds to a pathogen’s antigens to promote phagocytosis and make it easier for phagocytes to identify the pathogen.

Neutralization

The mechanism by which antibodies prevent a pathogen from adhering to host cells or bind to pathogenic toxins to prevent damage.

Antigen

Mostly glycoproteins or other proteins usually located on the outer surfaces of pathogens that can bind to an antibody and trigger antibody production.

Heteroantigen

Any antigen derived from one species (pathogen) that is able to stimulate an immune response in another species (host).

Self-antigens (autoantigens)

Normal constituents of an individual that can produce an immune response in that same individual under specific circumstances, such as tumor cells.

Agglutination

An uncontrollable clotting cascade that occurs during an immune response if incompatible blood is transfused.

Clonal expansion

The process by which activated B-cells divide by mitosis to produce large numbers of plasma B-cells.

Plasma cells

Differentiated B-cells capable of producing one specific type of antibody directed against an antigen presented by T-cells.

Memory cells

Long-lived lymphocytes that do not produce antibodies during first exposure but persist to immediately produce them upon a second infection.

HIV (Human Immunodeficiency Virus)

A virus transmitted via body fluids that destroys and depletes helper T-cells, weakening the adaptive immune system.

AIDS (Acquired Immunodeficiency Syndrome)

The last and most serious stage of HIV infection, where immunity is so weak that opportunistic infections occur.

Antibiotics

Chemicals that block bacterial processes like DNA replication, transcription, and translation, but do not affect eukaryotic cells or viruses.

Chemical libraries

Collections of compounds designed to interact with specific targets, used to screen for new potential antibiotics.

Zoonoses

Diseases and infections that are naturally transmitted between vertebrate animals and humans.

Herd immunity

Occurs when a large portion of a population is immune to a disease, impeding its spread; calculated by the formula $(1 - \frac{1}{R_0}) \times 100$.

Percentage change formula

The mathematical formula used for epidemiological analysis defined as $\frac{\text{final value} - \text{initial value}}{\text{initial value}} \times 100$.