BIOL 2252 Chapter 22: The Immune System

Flashcards covering key vocabulary and concepts from the lecture notes on the immune system.

Pathogenic

Infectious agents that can damage or kill a host

Bacteria

Prokaryotic, microscopic, single-celled organisms enclosed by a plasma membrane and cell wall.

Viruses

Microscopic structures containing DNA or RNA within a protein capsid; obligate intracellular parasites.

Fungi

Eukaryotic cells with a plasma membrane and cell wall that produce spores and release proteolytic enzymes.

Protozoans

Eukaryotic cells lacking a cell wall; intra- and extracellular parasites that interfere with normal cellular functions.

Multicellular parasites

Eukaryotic cells that live within a host, growing in size with nutrients provided by the host.

Prions

Small fragments of infectious proteins that cause disease in nervous tissue.

Leukocytes

White blood cells formed in red bone marrow.

Primary lymphoid organs

Bone marrow and thymus, where lymphocytes form and mature.

Secondary lymphoid structures

Lymph nodes, spleen, tonsils, MALT, lymphoid nodules, where T- and B- lymphocytes, macrophages, dendritic cells, and NK cells are housed.

Cytokines

Small proteins that regulate immune activity; chemical messengers released from one cell that bind to receptors of target cells.

Innate immunity

Present at birth, protects against a variety of different substances (nonspecific), and responds immediately.

Adaptive immunity

Acquired/specific immunity; response to an antigen involving specific T- and B- lymphocytes, taking several days to be effective.

First line of defense

The external body membranes (skin and mucosal membrane).

Second line of defense

Internal processes: activities of neutrophils, macrophages, dendritic cells, eosinophils, basophils, and NK cells; chemicals such as interferon and complement; and physiological processes such as inflammation and fever.

Third line of defense

Attacks particular foreign substances (takes longer to react than innate).

Mucin

Sticky mucus that lines digestive and respiratory tract traps microorganisms

Defensins

Antimicrobial peptides that inhibit microbial growth

Commensal microflora (normal microflora)

Microorganisms that reside on body surfaces – interfere with attachment

Phagocytes

Any white blood cells that ingest and digest foreign invaders- Neutrophils, macrophages, and dendritic cells

Opsonization

Immune system uses antibodies or complement proteins as opsonins that coat pathogens

Histamine

Increase vasodilation and capillary permeability

Heparin

Acts as an anticoagulant

Perforin

Create a transmembrane pore in unwanted cell

Granzymes

Enter pore and cause apoptosis of cell

Apoptosis

Cell death that causes shriveling rather than lysis

Complement system

Group of over 30 plasma proteins that work along with antibodies

Opsonin

Complement protein that binds to pathogen, enhancing likelihood of phagocytosis of pathogenic cell

Cytolysis

Complement triggers splitting of target cell

Membrane attack complex (MAC)

Complement proteins form membrane attack complex (MAC) that creates channel in target cell’s membrane

Inflammation

An immediate response to ward off unwanted substances.

Margination

Adherence of leukocytes to endothelial CAMs

Diapedesis

Cells escape blood vessel walls

Chemotaxis

Leukocytes migrate toward chemicals released from damaged, dead, or pathogenic cells

Pyrogens

Fever-inducing molecules

Adaptive immune system

A specific defensive system that involves specific lymphocyte responses to an antigen that eliminates most pathogens or abnormal cells in body

Antibody-mediated (Humoral) immunity

Involving B-lymphocytes, plasma cells, and antibodies

Cellular (cell-mediated) immunity

Involving T-lymphocytes

Antigens

Substances that can mobilize adaptive defenses and provoke an immune response by binding a T-lymphocyte or antibody

Antigenic determinants

Parts of antigen that antibodies or lymphocyte receptors bind to

Self-antigens

Body’s own molecules that typically do not bind immune components

Antigenic determinant/epitope

Specific site on antigen recognized by immune system

Immunogenicity

Ability to trigger response that increases with antigen’s degree of foreignness, size, complexity, or quantity

Haptens

Too small to function an antigen alone; become immunogenic when attached to carrier molecule

MHC proteins

Group of glycoproteins that are coded by genes of major histocompatibility complex (MHC) and unique to each individual

Antigen-presenting cells (APCs)

Present to both helper T-cells and cytotoxic T-cells

Helper T-lymphocytes

CD4+ cells that assist (“help”) in cell-mediated, antibody-mediated, and innate immunity

Cytotoxic T-lymphocytes

CD8+ cells that release chemicals that destroy other cells

TCR (T-cell receptor)

Antigen receptor of T-lymphocyte

BCR (B-cell receptor)

Antigen receptor of B-lymphocyte

MHC class I molecules

Have genetically determined structure that is unique to individual that display fragments of proteins that were bound in RER

MHC class II molecules

From exogenous antigens brought into cell through endocytosis with fragments “loaded” onto MHC class II molecules within vesicle

Activation of lymphocytes

Becoming activated and replicate to form identical lymphocytes

Effector response

Action of lymphocytes to eliminate antigen

Thymic selection

Eliminates 98% of T-cells produced

Negative selection

Prompts apoptosis of T cells that bind to self-antigens displayed by self-MHC proteins

Positive selection

Selects T cells capable of recognizing self-MHC proteins (MHC restriction)

Immunocompetent

Bind antigen and respond to it

Naive T-lymphocyte

Not yet exposed to antigens they recognize

Regulatory T-lymphocytes (Tregs)

cd4+ cells formed from T-cells that bind self- antigens that inhibit immune response

Clonal selection

Forming clones in response to an antigen

Antigen challenge

First encounter between antigen and lymphocyte

Where dose activation of helper T-lymphocytes occur

In secondary lymphoid structure

Antibody titer

Circulating blood concentration of antibody against a specific antigen

Antibodies

Also called Immunoglobulins (Igs)—are proteins secreted by plasma cells against a particular antigen

Neutralization

Antibody physically covers antigenic determinant of pathogen and blocks binding site

Agglutination

Allows for antigen-antibody complexes to become cross-linked into large lattice-like clumps (very effective against bacteria)

Precipitation

Antibody cross-links circulating antigens (for example, viral particles), complexes precipitate which are easier for phagocytes to engulf

Complement fixation

Alignment triggers complement fixation, which leads to cell lysis

Opsonization

Fc region of the antibody binds to receptors of phagocytic cells making it more likely to be “seen”, triggering phagocytosis

Activation of NK cells

Fc region of antibody beings to NK cell, triggering release of cytotoxic chemicals a process called antibody-dependent cell-mediated cytotoxicity (ADCC)

Primary immune response

Involves a lag period: 3 to 6 days when Adaptive immunity activation requires contact between lymphocyte and antigen

Secondary immune response

Re-exposure to same antigen gives faster, more prolonged, more effective response- powerful secondary response

Active humoral immunity

Occurs when B cells encounter antigens and produce specific antibodies against them; direct encounter with pathogen

Passive humoral immunity

Occurs when ready-made antibodies are introduced into body

Herd immunity:

Resistance of members within a population to a disease