Lymphatic System, Immunity, and Microbiology Practice Flashcards

Vocabulary-style flashcards covering the lymphatic system, innate and adaptive immunity, and the basic characteristics of infectious microbiological agents based on HUBS 1401 lecture notes.

Lymphatic System

A system of organs, tissues, nodes, vessels, and fluid (lymph) that drains excess interstitial fluid, transports dietary lipids, and facilitates immune response.

Lymphatic Capillaries

Blind-ended tubes with overlapping endothelial cells forming mini-valves located between cells to drain fluid, proteins, and larger particles like bacteria and viruses.

Lymph Nodes

Kidney-shaped organs, around $600$ in total and up to $25\,mm$ in diameter, that filter lymph flowing in one direction.

Primary Lymphatic Organs

Sites of stem cell division and production of immunocompetent cells, specifically red bone marrow and the thymus.

Secondary Lymphatic Organs and Tissues

Sites where the majority of immune responses occur, including lymph nodes, the spleen, and lymphatic nodules.

Innate Immunity

The first and second lines of nonspecific defense present at birth, including barriers (skin, mucus), inflammation, fever, and some white blood cells.

Lysozyme

An antimicrobial enzyme found in tears and saliva that acts as part of the first line of defense.

Phagocytes

Cells, chiefly neutrophils and macrophages (which circulate as monocytes), that migrate to sites of infection via chemotaxis to engulf microbes.

Natural Killer Cells

Lymphocytes representing $5-10\%$ of blood lymphocytes that release perforins to form membrane perforations and granzymes to digest target cells.

Inflammation

A second-line defense response causing pain, redness, heat, and swelling, triggered by inflammatory mediators like histamine to rid the area of pathogens.

Chemotaxis

The process of recruiting phagocytes and other cells to an area of damage or infection.

Fever

An abnormally high body temperature caused by pyrogens that cause the hypothalamus to turn up the body’s thermostat.

Interferons (IFNs)

Proteins released by virus-infected cells that stimulate neighboring cells to synthesize proteins that interfere with viral replication.

Complement System

A system of >30 plasma proteins that assist the immune response through opsonization, membrane lysis, and increasing inflammation.

Opsonization

The process where antibodies or complement proteins bind to the surface of a microbe to facilitate phagocytosis.

Adaptive Immunity

The third line of defense that recognizes specific antigens, is systemic in action, and possesses a memory for future infections.

Antigen

Any substance (an antibody generator) recognized by the adaptive immune system that induces a response or antibody production.

Major Histocompatibility Complex (MHC)

Self-antigens found on an individual's own cells that distinguish them from foreign entities.

Antigen Presenting Cells

Cells such as dendritic cells, macrophages, and B cells that engulf pathogens and display antigen-MHC complexes to immune cells.

Humoral Immunity

Antibody-mediated immunity where B cells and plasma cells produce antibodies to defend against extracellular pathogens.

Cell-Mediated Immunity

Immune response where active cytotoxic T cells defend against intracellular pathogens, cancers, and transplant tissues.

Plasma Cells

Cells derived from B cells that secrete antibodies specific to an antigen.

IgG

The majority of antibodies in serum and the only class that can cross the placenta from mother to fetus.

IgA

Antibodies found in secretions such as breast milk and saliva that function in agglutination and neutralization.

IgM

The first antibody secreted upon exposure to an antigen; it is a potent agglutinating and precipitating agent.

IgE

Antibodies that bind to mast cells and basophils to trigger degranulation and facilitate inflammation, particularly in allergic responses.

Helper T Cells (CD4+)

Cells that recognize foreign antigens on APCs and produce cytokines to activate other T cells and B cells.

Cytotoxic T Cells (CD8+)

Cells specialized in killing virus-infected, cancer, or foreign graft cells by releasing perforin and granzymes.

T Regulatory Cells (CD4+, CD25+)

Cells that help distinguish self from nonself molecules and suppress immune activity once a target is destroyed to reduce autoimmune risks.

Fungi

Eukaryotic organisms with rigid cell walls (chitin-glucan) that can be unicellular (yeasts) or multicellular (moulds).

Protozoa

Unicellular eukaryotes, sized between $20-50\,\mu m$ up to $1\,mm$, many of which are mobile and feed by engulfing smaller organisms.

Bacteria

Prokaryotic organisms without a nucleus or membrane-bound organelles, such as Escherichia coli or Porphyromonas gingivalis.

Viruses

Sub-microscopic, obligate intracellular parasites that consist of DNA or RNA surrounded by a protein shell (capsid).

Haemagglutinins (H)

Antigenic glycoproteins on the viral surface of influenza that bind the virus to a host cell.

Neuraminidase (N)

Enzymes on the influenza viral surface that act on infected cell surfaces to release viral progeny.