Marieb Human Anatomy & Physiology Chapter 21: The Immune System

A comprehensive set of vocabulary flashcards covering Chapter 21 of Marieb's Human Anatomy & Physiology, focusing on innate and adaptive immunity, cell types, antibody classes, and clinical homeostatic imbalances.

Immunity

The resistance to disease provided by the three lines of defense in the immune system.

Surface barriers

The first line of defense consisting of intact skin and mucosae, providing structural barriers to keep invaders out.

Acid mantle

The acidity of skin, vaginal, and stomach secretions that inhibits bacterial growth.

Lysozyme

An enzyme found in saliva, respiratory mucus, and lacrimal fluid that kills many microbes.

Defensins

Broad-spectrum antimicrobial peptides secreted in response to inflammation and barrier breach that inhibit microbial growth.

Pattern recognition receptors

Receptors used by the second line of defense to identify potential pathogens by binding to specific-shaped molecules not found on human cells.

Toll-like receptors (TLRs)

A class of pattern recognition receptors, of which humans have $11$, that play a central role in triggering immune responses.

Neutrophils

The most abundant phagocytes that phagocytize infectious material in tissues.

Macrophages

The most voracious phagocytes; they include free macrophages that wander through tissues and fixed macrophages like stellate macrophages in the liver.

Phagolysosome

A structure formed during phagocytosis when a phagosome fuses with a lysosome to digest its contents.

Respiratory burst

Process stimulated by helper T cells where macrophages kill resistant pathogens by releasing free radicals and oxidizing chemicals like $H_2O_2$.

Opsonization

The process of coating pathogens with opsonins (complement proteins or antibodies) to provide "handles" for phagocytes to grab.

Netosis

A process where neutrophils release a sticky net of their own DNA and proteins to trap and kill extracellular pathogens, destroying themselves in the process.

Natural Killer (NK) cells

Large granular, nonphagocytic lymphocytes that induce apoptosis in cancer and virus-infected cells lacking "self" MHC proteins.

Inflammation

A nonspecific tissue response to injury that prevents the spread of pathogens, disposes of debris, and alerts the adaptive immune system.

Hyperemia

Increased blood flow to an area caused by local vasodilation, resulting in the redness and heat associated with inflammation.

Exudate

Fluid containing clotting factors and antibodies that seeps from blood into tissue during inflammation, causing local swelling or edema.

Leukocytosis

An increase in the number of white blood cells (WBCs) in the bloodstream, a characteristic sign of inflammation.

Margination

The process where phagocytes cling to the inner walls of capillaries and postcapillary venules.

Diapedesis

The process by which neutrophils flatten and squeeze between endothelial cells to exit the bloodstream.

Chemotaxis

The movement of white blood cells toward an injured area in response to inflammatory chemicals acting as chemotactic agents.

Abscess

A pocket of pus walled off by collagen fibers if inflammation fails to eliminate debris.

Granulomas

Tumorlike growths consisting of infected macrophages surrounded by healthy macrophages and a fibrous capsule, often seen in resistant infections like tuberculosis.

Interferons (IFNs)

Immune modulating proteins produced by virus-infected cells that block viral replication in healthy neighboring cells.

Complement system

A group of at least $20$ plasma proteins that circulate in an inactive state and, when activated, amplify inflammation and lyse certain bacteria.

Membrane attack complex (MAC)

A group of complement proteins ($C5b$ and $C6$-$C9$) that insert into a target cell membrane, creating pores that cause cell lysis.

Pyrogens

Chemicals secreted by leukocytes and macrophages that act on the hypothalamus to raise body temperature, causing fever.

Humoral immunity

Also called antibody-mediated immunity, this adaptive arm uses antibodies in the body's fluids to bind to extracellular targets.

Cellular immunity

Also called cell-mediated immunity, this adaptive arm involves lymphocytes directly killing target cells or releasing chemicals to manage the immune response.

Antigens

Substances that mobilize adaptive defenses and provoke an immune response; short for "antibody generating."

Immunogenicity

The functional property of a complete antigen that allows it to stimulate the proliferation of specific lymphocytes.

Haptens

Incomplete antigens; small molecules that are not immunogenic unless they attach to a protein carrier.

Antigenic determinants

The specific parts of an antigen that are immunogenic and to which antibodies or lymphocyte receptors bind.

MHC proteins

Glycoproteins unique to individuals that display either self- or foreign antigens; T lymphocytes can only bind antigens presented on these proteins.

Immunocompetence

The state in which a lymphocyte is able to recognize its specific antigenic determinant by displaying unique antigen receptors.

Self-tolerance

The requirement that lymphocytes remain relatively unresponsive to self-antigens to prevent attacking the body's own cells.

Clonal selection

The process where the first encounter between a naive lymphocyte and an antigen stimulates the lymphocyte to develop and activate.

Somatic recombination

The shuffling and combining of gene pieces to form up to $1$ billion different types of antigen receptors in lymphocytes.

Antigen-presenting cells (APCs)

Cells like dendritic cells, macrophages, and B cells that engulf antigens and display fragments for T cells to recognize.

Plasma cells

Antibody-secreting effector B cells that produce antibodies at a rate of approximately $2000$ per second.

Antibody titer

The concentration of plasma antibodies in the blood, which peaks much higher during a secondary immune response.

Active humoral immunity

A type of immunity where B cells encounter antigens and produce antibodies, either naturally through infection or artificially through vaccines.

Passive humoral immunity

A type of immunity where borrowed antibodies are introduced to the body, providing immediate but limited protection without creating memory cells.

Antibodies

Also called immunoglobulins ($Igs$), these are proteins secreted by plasma cells that bind specifically with antigens.

IgG

The most abundant antibody in plasma ($75-85$\%$$) and the main antibody of both secondary and late primary responses; it can cross the placenta.

IgM

The first antibody class released during a primary response and a potent agglutinating agent.

IgA

The "secretory" antibody found in body secretions like saliva and milk that helps prevent pathogen attachment to epithelial surfaces.

Neutralization

An antibody mechanism where specific sites on viruses or bacterial exotoxins are blocked so they cannot bind to body cells.

Agglutination

An antibody mechanism where antigens are cross-linked into clumps, enhancing phagocytosis.

Precipitation

An antibody mechanism where soluble molecules are cross-linked into large complexes that settle out of solution.

Monoclonal antibodies

Pure antibody preparations specific for a single antigenic determinant, produced commercially for research and clinical testing.

Helper T ($T_H$) cells

CD4 effector cells essential for mobilizing both humoral and cellular immunity by activating B cells, T cells, and macrophages.

Cytotoxic T ($T_C$) cells

CD8 effector cells that directly attack and kill infected or abnormal cells using perforins and granzymes.

Regulatory T ($T_{Reg}$) cells

T cells that dampen the immune response and are important for preventing autoimmune reactions.

Anergy

A state of unresponsiveness in T cells that occurs if they bind to an antigen without receiving co-stimulatory signals.

Cytokines

Chemical messengers like interferons and interleukins that influence cell development and immune system responses.

Severe combined immunodeficiency (SCID) syndromes

Congenital disorders resulting in a marked deficit in B and T cells due to genetic defects.

AIDS

Acquired immune deficiency syndrome; a condition caused by HIV that destroys $T_H$ cells, disabling the adaptive immune system.

Autoimmune disease

A condition where the immune system fails to distinguish self from foreign antigens, producing autoantibodies that destroy the body's own tissues.

Hypersensitivities

Immune responses to perceived threats that cause tissue damage; includes immediate/acute allergies and delayed reactions.