Ch. 1 - Overview of the Immune System

What has to be involved for the process of pathogen recognition?

An interaction between the foreign organism and a recognition molecule expressed by host cells.

What are T cell receptors?

Antigen-binding molecule expressed on the surface of T-cells

What triggers clonal selection?

Antigens binding to the surface receptors of B and T cells.

What is immunodeficiency?

Any deficiency in the immune response, whether inherited or acquired.

What are cytokines?

Any numerous secreted, low-molecular weight proteins that regulate the intensity and duration of the immune response by exerting a variety of effects on lymphocytes and other immune cells that express the appropriate receptor.

What is an antigen?

Any substance (usually foreign) that binds specifically to an antibody or a T cell receptor.

What are B lymphocytes (B cells)?

Lymphocytes that matures in the bone marrow and express membrane-bound antibodies. After interacting with antigen, they differentiate into antibody-secreting plasma cells and memory cells.

What is an antiserum?

Serum from animals immunized with antigen that contains antibodies to that antigen.

What is a consequence of generating random recognition receptors?

Some could recognize and target the host.

What are T helper cells (Th cells)?

T cells that are stimulated by antigen to provide signals that promote immune responses.

What does successful maintenance of tolerance ensure?

That the host always knows the difference between self and non-self.

What is immunologic memory?

The ability of the immune system to respond much more swiftly and with greater efficiency during a second, or later exposure to the same pathogen.

Why does the adaptive immunity take longer than the innate immunity?

The immune response is much more antigen specific and more attuned to subtle molecular differences. Thus, providing a second and more comprehensible line of defense, informed by the struggles undertaken by the innate system.

How is tolerance utilized by the immune system?

To avoid recognizing and destroying host tissues.

What are the five major categories of human pathogens? (Describe what they are)

Viruses - Obligate intracellular pathogens Bacteria - Intra/Extracellular Prokaryotes Parasites - Worms/protozoans Fungi - Eukaryotic Cancer

What three characteristics depends on which cells and molecules become activated during an immune response?

1) Chemical structure present on the pathogen 2) Whether it resides inside or outside of host cells 3) Location of the response

What is a pathogen?

A disease-causing infectious agent

What are autoimmune diseases?

A group of disorders caused by the action of ones own antibodies or T cells reactive against self proteins

What are T lymphocytes (T cells)?

A lymphocyte that matures in the thymus and expresses a T-cell receptor, CD3 and CD4 or CD8.

What is a vaccine?

A preparation of immunogenic material used to induce immunity against pathogenic organisms

What is tolerance?

A state of immunologic unresponsiveness to particular antigens or sets of antigens.

What is immunity?

A state of protection from infectious diseases

What happens during the first and second encounter with a foreign antigen in the adaptive immunity?

Adaptive immunity undergoes a primary response, during which the key lymphocytes that will be used to eradicate the pathogen are clonally selected, honed, and enlisted to resolve the infection. During a second response, memory cells are re-stimulated to fight again.

How does 'danger' hypothesis disprove the self vs non-self hypothesis?

Against the self-non-self theory, the danger theory claims that self constituents can trigger an immune response, if they are dangerous; and non-self constituents can be tolerated, if they are not dangerous.

What are cytotoxic T lymphocytes (CTLs or Tc cells)?

An effector T cell that can mediate the lysis of target cells bearing antigenic peptides complexed with a class 1 MHC molecule.

What is the difference between cell-mediated immunity and humoral immunity?

Cell-mediated Immunity- Host defenses that are mediated by antigen-specific T cells. It protects against intracellular bacteria, viruses, and cancer. Humoral Immunity-Host defenses that are mediated by antibody present in the plasma, lymph, and tissue fluids. It protects against extracellular bacteria and foreign macromolecules.

What immune response are T cells associated with?

Cell-mediated immunity

What are phagocytes?

Cells with the capability to internalize and degrade microbes or particulate antigens.

What is the difference between central tolerance and peripheral tolerance?

Central tolerance - helps to keep these ant-self recognition molecules/cells from circulating in the bloodstream. Peripheral tolerance - Helps limit the damage due to anti-self cells in circulation

What is the 'danger' hypothesis?

Claims that the immune responses are triggered by 'danger' signals released by the body's own cells. According, to the danger theory every immune response is not due to the presence of 'non-self', but to the emission, within the organism, of 'danger signals.'

Does active immunity need a competent immune system?

Competent immune system needed

Does passive immunity need a competent immune system?

Competent immune system not needed

What are B cell receptors?

Complex comprising a membrane-bound antibody

What does attenuation mean?

Decrease in the virulence of a pathogen and render it incapable of causing disease.

What is hypersensitivity?

Exaggerated immune response that causes damage to the individual.

Which two immune responses are involved in adaptive immunity?

Humoral immune response Cell-mediated immune response

What immune response are B cells associated with?

Humoral response

What is the difference between the innate immune response and the adaptive immune response?

Innate Immunity - Non-antigen specific host defenses that exist prior to exposure to an antigen and involve anatomic, physiologic, endocytic and phagocytic, anti-microbial, and inflammatory mechanisms. Exhibits no adaptation or memory characteristics. Adaptive Immunity - Host defenses that are mediated by B cells and T cells following exposure to antigen and that exhibit specificity, diversity, memory, and self-non-self discrimination.

Why is the innate immune response highly effective as a first line of defense?

It prevents most pathogens from taking hold, or eliminates infectious agents within hours of encounter

Explain how Edward Jenner and Louis Pasteur made advancements in the development of immunity.

Jenner targeted smallpox. He inoculated an 8 year old boy with the mild disease cowpox. After he introduced smallpox and the boy did not develop smallpox. Pasteur inoculated chickens with a weakened form of cholera. After introducing those same chickens to the real disease, the chickens did not become infected.

What are memory cells and how are they associated with an immune response?

Lymphocytes generated following encounters with antigen that are characteristically long lived. These cells almost immediately begin where they left off, continuing to learn and improve their eradication strategy during each subsequent encounter with the same antigen.

What are pathogen-associated molecular patterns (PAMPs)?

Molecular patterns common to pathogens but not occurring in mammals. PAMPs are recognized by various pattern-recognition receptors of the innate immune system.

Describe the life span of passive vs active immunity and provide an example.

Passive Immunity- It is short-lived and limited, as the cells that produce these antibodies are not being transferred. ex. Breast milk Active Immunity- Can supply the individual with renewable, long-lived protection from the specific infection ex. One's own immunity.

What is the difference between passive and active immunity?

Passive Immunity-Temporary adaptive immunity conferred by the transfer of immune products, such as antibody(antiserum), from an immune individual to a non-immune one. Active Immunity-Adaptive immunity that is induced by natural exposure to a pathogen or by vaccination.

Why is the host-pathogen interactions an ongoing arms race?

Pathogens evolve to express unique structures that avoid host detection. The host germline encoded recognition system co-evolves to match new challenges.

What are physical, chemical, and molecular barriers of the innate immunity response?

Physical - Skin, tears, sweat Chemical - Stomach acids Molecular - PRRs (results in phagocytosis or destruction of pathogen)

What is the difference between primary immunodeficiency and secondary immunodeficiency?

Primary Immunodeficiency - An inherited genetic or development defect in some components of the immune system. Secondary Immunodeficiency - Loss of immune function that results from exposure to an external agent, often an infection.

What is an immunoglobulin?

Protein consisting of two identical heavy chains and two identical light chains, that recognize a particular epitope of an antigen and facilitates clearance of that antigen. (Same as antibody)

What is an antibody?

Protein consisting of two identical heavy chains and two identical light chains, that recognize a particular epitope of an antigen and facilitates clearance of that antigen. (Same as immunoglobulin)

Why are pattern recognition receptors (PRRs) germline-encoded recognition molecules?

Provide a first line of defense for the quick detection of many typical chemical identifiers carried by the most common invaders.

What are pattern recognition receptors (PRRs)?

Receptors if the innate immune system that recognize molecular patterns (PAMPs) present on pathogens but absent in the host

What is clonal selection?

The antigen-mediated activation and proliferation of B cells and T cells. The ensuing proliferation of the selected clone of cells creates an army of cells all with the same receptor and responsible for binding more of the same receptor and responsible for binding more of the same antigen, with the ultimate goal of destroying the pathogen.

What is the immune system?

The cells and molecules that are responsible for immunity

What is phagocytosis?

The cellular uptake of particulate materials by engulfment

What is an immune response?

The coordinated response to the introduction of foreign substances.

What is an epitope?

The portion of an antigen that is recognized and bound by an antibody or TCR-MHC combination.

What is the Self vs Non-Self Theory?

The theory that explains how the immune system only attacks anything it does not recognize as self.

What is herd immunity?

When the majority of the population is immune to an infectious agent, thus significantly reducing the pathogen reservoir due to the low chance of a susceptible individual contacting an infected individual.