Immune and Lymphatic System Vocabulary

Comprehensive vocabulary flashcards covering the key terms, cells, molecules, and physiological structures of the immune and lymphatic systems based on the lecture notes.

Pathogens

Disease-causing organisms, which include bacteria, viruses, fungi, and parasites.

Immunity

The ability of the host body to resist pathogen efforts to cause disease and to defend against infection and internal threats.

Lymph

A clear, colorless fluid—similar to plasma but containing roughly half the plasma proteins—originating as extracellular fluid drawn into lymphatic capillaries.

Lacteals

Specialized lymphatic capillaries located in the small intestine that transport lipids absorbed by the digestive tract.

Lymphedema

Severe tissue swelling caused by an obstruction of lymphatic vessels that prevents normal lymph drainage.

Cisterna Chyli

A prominent expanded sac at the base of the thoracic duct that receives lymph from the inferior abdomen, pelvis, and lower limbs.

Thoracic Duct

The larger lymphatic collecting vessel that originates at the cisterna chyli and drains lymph from all body regions inferior to the diaphragm and from the left side superior to the diaphragm into the left subclavian vein.

Right Lymphatic Duct

The lymphatic collecting vessel that receives lymph from the right arm, right side of the head, and right thorax, emptying into the right subclavian vein.

Innate Immunity

General, nonspecific defenses present at birth that respond the same way to any pathogen threat without distinguishing specific molecular structures.

Adaptive Immunity

Specific immune protection developed after exposure to particular antigens, mediated by T cells and B cells.

Natural Killer (NK) Cells

Large granular lymphocytes that perform immune surveillance by recognizing and directly lysing abnormal target cells, such as virus-infected or cancer cells.

Perforins

Proteins released by NK cells and cytotoxic T cells via exocytosis that punch holes in an abnormal cell's plasma membrane to disrupt its concentration gradient and cause cell lysis.

Interferons (IFNs)

A class of cytokine proteins released by virus-infected cells and activated immune cells that stimulate neighboring uninfected cells to produce anti-viral proteins.

Complement System

A system of over 30 circulating plasma proteins that enhance antibody action, trigger cell lysis, stimulate histamine-mediated inflammation, and promote opsonization.

Opsonization

The coating of pathogen surfaces with complement proteins or antibodies to facilitate binding and engulfment by phagocytes.

Cardinal Signs of Inflammation

The four localized tissue indicators of inflammation: redness (erythema), swelling (edema), heat, and pain.

Pyrogens

Fever-inducing agents—including bacterial products and endogenous cytokines like IL-1, interferons, and TNF—that cause the hypothalamus to raise body temperature above $37.2^\text{o}\text{C}$ ($99^\text{o}\text{F}$) or $38^\text{o}\text{C}$ ($100.4^\text{o}\text{F}$).

Positive Selection

The thymic process in the cortex where developing T cells are tested for their ability to recognize foreign antigens and APCs; surviving cells become immunocompetent.

Negative Selection

The thymic process in the medulla that eliminates self-reactive T cells via clonal deletion or anergy to ensure self-tolerance.

Clonal Deletion

A self-tolerance mechanism in which self-reactive T cells or B cells undergo programmed cell death and are phagocytized by macrophages.

Anergy

A state of non-responsiveness in self-reactive lymphocytes where cells remain alive but permanently inactive.

Immunocompetence

The functional ability of mature lymphocytes to recognize and bind to specific foreign antigens.

Mucosa-Associated Lymphatic Tissue (MALT)

Diffuse lymphatic tissue aggregations located in the connective tissues of mucous membranes protecting body passages open to the external environment.

Antigen-Presenting Cells (APCs)

Specialized cells—such as macrophages, dendritic cells, reticular cells, and B cells—that internalize antigens, process them, and display antigen fragments on surface MHC proteins.

Major Histocompatibility Complex (MHC) Proteins

Genetically coded surface glycoproteins that serve as cell identification tags and bind antigen fragments for presentation to T lymphocytes.

Class I MHC Proteins

Surface proteins produced by all nucleated body cells that present endogenous antigens to CD8 cytotoxic T cells.

Class II MHC Proteins

Surface proteins found exclusively on antigen-presenting cells and lymphocytes that present exogenous antigens to CD4 helper T cells.

CD3 Receptor Complex

A membrane protein complex present on all T lymphocytes that is required for T cell activation.

CD8 Markers

Surface proteins found on cytotoxic T cells and regulatory T cells that bind specifically to Class I MHC proteins.

CD4 Markers

Surface proteins found on helper T cells that bind specifically to Class II MHC proteins.

Cytotoxic T Cells

CD8-positive T lymphocytes that directly attack foreign or virus-infected host cells by secreting perforins, lymphotoxins, and apoptotic cytokines.

Helper T Cells

CD4-positive T lymphocytes that secrete cytokines to stimulate and coordinate both cell-mediated and antibody-mediated immune responses.

Regulatory T Cells

CD8-positive T lymphocytes that secrete suppression factors to moderate and limit the extent of an immune response.

Cytokines

Chemical messengers secreted by immune system cells and damaged tissue cells that coordinate localized and systemic immune responses.

Interleukins (ILs)

A major class of cytokines produced by lymphocytes and macrophages that enhance T cell sensitivity, promote antibody secretion, stimulate inflammation, and induce fever.

Tumor Necrosis Factors (TNFs)

Cytokines secreted by macrophages and cytotoxic T cells that slow tumor growth, kill tumor cells, promote eosinophil activity, and act as pyrogens.

IgG

The most abundant class of circulating immunoglobulins (80%), responsible for protection against viruses and bacteria, and capable of crossing the placenta to confer passive immunity to the fetus.

IgM

The first antibody class secreted following antigen exposure, circulating as a star-shaped pentamer; includes anti-A and anti-B blood agglutinins.

IgA

An immunoglobulin found primarily in glandular secretions (mucus, tears, saliva, semen) that neutralizes pathogens before they gain entry to internal tissues.

IgE

An immunoglobulin bound to the surface of basophils and mast cells that triggers histamine and heparin release upon binding an antigen, driving allergic and inflammatory reactions.

IgD

An immunoglobulin located on the surface of B cells that binds extracellular antigens to assist in B cell sensitization.

Epitope

The specific portion or antigenic determinant site of an antigen molecule to which an antibody or T cell receptor attaches.

Hapten

A partial antigen that is incapable of stimulating an immune response on its own unless bound to a larger carrier molecule.

Primary Response

The initial antibody-mediated response following first exposure to an antigen, characterized by a slow rise in antibody titer peaking in about two weeks.

Secondary Response

The rapid and pronounced immune response upon repeat exposure to a previously encountered antigen, driven by memory cells that rapidly produce massive quantities of IgG.

Anaphylaxis

A severe, systemic allergic reaction caused by circulating allergens binding to IgE on mast cells and basophils, resulting in extensive vasodilation, airway constriction, and potential shock.