Chapter 10 - The Immune System

Question 1

Innate immunity (mode of defense)

Answer 1

Defends the host from infection by other organisms in an immediarte and non-specific manner. Cells of the innate system recognize and respond to pathogens in a generic way through phagocytosis and cytokine release, which triggers an inflammatory response that recruits more phagocytes. Does not confer long-lasting or protective immunity to the host.

Question 2

Adaptive Immunity (mode of defense)

Answer 2

The acquired immune system. Composed of highly specialized, systemic cells and processes that eliminate or prevent pathogen growth. Creates immunological memory after an initial response to a specific pathogen, leading to an enhanced response to subsequent encounters with that same pathogen. Includes components of both humoral (B-cels) and cell-mediated (T-cells) immunity.

Question 3

Leukocytes

Answer 3

White blood cells; the component of blood involved in cell defense and immunity. Comprise both the active and innate immune systems. Basophils, neutrophils, and eosinophils are granular leukocytes; monocytes, megakaryocytes, and lymphocytes (B- and T-cells) are agranular leukocytes.

Question 4

Lymphatic system

Answer 4

A system of vessels and lymph nodes that collect interstitial fluids and return them to the circulatory system, thereby maintaining a plasma protein and fluid balance. The lymphatic system is also involved in lipid absorption and lymphocyte maturation (Thymus = T-cells; Spleen = B-cells).

Question 5

Lymphatic Flow (Diagram)

Answer 5

Question 6

Lymph nodes

Answer 6

Swellings along the lymph vesses where lymph is filtered by leukocytes to remove antigens.

Question 7

Lymphatic capillaries

(diagram)

Answer 7

Question 8

Granular leukocytes

Answer 8

Named because cytoplasmic granules that are visible by light microscopy, these consist of neutrophils, eosinophils, basophils. Granular leukocytes mount nonspecific, innate immune responses such as inflammatory reactions, allergies, pus formation, and destruction of bacteria and parasites.

Question 9

Agranular leukocytes

Answer 9

Named because they do not contain cytoplasmic granules, these consist of monocytes and lymphocytes.

• *Monocytes** mature into macrophages, which phagocytose foreign matter such as bacteria.
• *Lymphocytes** are important in specific immune responses against viruses and bacteria. Lymphocytes mature into B- and T-cells.

Question 10

B-Cells

Answer 10

Lymphocytes that mature in the spleen or lymph nodes. B-cells are responsible for antibody generation.

Question 11

T-Cells

Answer 11

Lymphocytes that mature in the thymus, T-cells kill infected cells and activate others. There are four types of T-cell: helper, memory, suppressor, and killer T cells.

Question 12

Active immunity

Answer 12

Immunity resulting from the production of antibodies during a previous infection or a vaccination.

Question 13

Primary response

Answer 13

The initial response to a specific antigen. During primary response, T and B lymphocytes are activated adn specific antibodies and memory cells to the antigen are produced.

Question 14

Secondary response

Answer 14

Subsequent infections by antigens trigger more immediate response by the memory cells produced during primary response

Question 15

Passive immunity

Answer 15

A short-lived immunity resulting from the transfer of antibodies into an individual who does not produce those antibodies

Question 16

Humoral immunity

Answer 16

The synthesis of specific antibodies by activated B-cells in response to an antigen. These antibodies bind to the antigen and either clump together to become insoluble or attract other cells that engulf them.

Question 17

Inflammation

Answer 17

First reaction to tissue injury / infection. Blood vessel dilation, capillary permeability, swelling, migration of granulocytes and macrophages. Purpose: sequester affected tissue and keep infection from spreading.

Question 18

Immunoglobulins

Answer 18

A protein antibody produced in response to a specific foreign substance that recognizes and binds to that specific antigen and triggers an immune response.

Question 19

What are the divisions of the immune system

Answer 19

• Innate immune system – inflammatory molecules and various phagocytes. Non-specific, immediate respone.
• Adaptive immune system – Based on antigen recognition. Specific, mediated response.
  
  • Humoral immunity – B-cell mediated; Antibody secretion.
  • Cell-mediated immunity – T-cell mediated; direct interation with pathogen or infected cell.

Question 20

Blood cell differentiation diagram

Answer 20

Question 21

What are the four major organs of the immune system?

Answer 21

1. Lymph Nodes - filter lymph and help attack bacteria and viruses
2. **Bone Marrow **- immune cell production
3. **Thymus **- secretes thymosin, a hormone that stimulates pre-T cells to mature
4. Spleen - storage area for blood; filters blood and lymph

Question 22

autoimmunity

Answer 22

Occurs when the immune system fails to distinguish between self and foreign, and attacks self-antigens as if they were foreign. Type I diabetes results from pancreatic ß-cells being attacked by the immune system, resulting in an insulin deficiency; such patients must receive insulin replacement therapy for the remainder of their lives.

Question 23

Allergies

Answer 23

Occur when the immune system recognizes a foreign particle as dangerous when, in fact, it is not. Hypersensitivity to these antigens results in overactivation of the immune system when these antigens are encountered.

Question 24

Innate Immune System - Cell Types and Functions

Answer 24

• Macrophage - engulfs and consumes pathogen invaders
• Mast Cell - releases histamine and other pro-inflammatory chemicals
• Granuocyte - neutrophils, basophils, and eosinophils; participate in the inflammatory response
• Dendritic Cell - phagocytose pathogens; function in antigen-presentation to adaptive immune cells
• Natural Killer Cell - destroys pathogen-infected cells of the body

Question 25

Adaptive Immune System - Cell Types and Functions

Answer 25

• B-Cell - Antigens stimulate B-cell proliferation and antibody production to neutralize pathogens or mark them for destruction. Memory B-cells protect against future infection.
• Killer T-Cell (CD8+) - destroys an infected cell on which it detects antigens by secreting toxic chemicals into the infected cell. Memory cytotoxic T-cells protect against future infection.
• Helper T-Cell (CD4+) - coordinate the immune response through lymphokine secretion to recruit other immune cells and increase their activity
• Suppressor T-Cell - tones down immune response once infection has been contained

Question 26

T-cell: mode of antigen recognition

Answer 26

T-Cell Receptor (TCR) on T-cell recognizes and binds specific antigens that have been presented by MHC I molecules on the target cell’s surface. If binding occurs (antigen recognition), the T-cell will destroy the target cell.

Question 27

Absence of B-cells: pathology?

Answer 27

Bruton’s agammaglobulinemia is characterized by the absence of B-cells. Lack of B-cells results in the absence of circulating antibodies once the passive immunity conferred by placental transfer of antibodies from the mother subsides. Results in recurrent bacterial infection beginning at 8-9 months. Defenses against viral and fungal infections are normal since these microorganisms are typically handled by T-cells.

Question 28

Absence of T-cells: Pathology?

Answer 28

DiGeorge’s syndrome is a selective T-cell disorder resulting from the underdeveoplment or absence of the thymus gland. Circulating antibody levels are normal, but these children have imparired defenses against viral and fungal infections.

Question 29

Immunoglobulins: structure

Answer 29

Y-shaped molecules comprised of two identical heavy chains and two identical light chains bound together by disulphide linkages. The antigen-binding region at the two tips of the Y is variable and confers specificity to the antibody. The constant region at the stem of the Y is invariable and is involved in recruitment and binding of other immune modulators (e.g. macrophages).

Question 30

How many antibodies does each B-cell produce?

Answer 30

Each B-cell makes only one antibody. The wide range of antigens recognized by the humoral immune system results from a large number of B-cells each generating unique antibodies against different antigens.

Question 31

How is long-term immunity maintained?

Answer 31

Upon exposure to the correct antigen, B-cells will proliferate and differentiate into two types of B-cells:

**Plasma cells - **produce large amounts of antibody and mount a primary response

**Memory cells - **remain in the lymph nodes, perhaps for the life of the organism. Upon re-exposure to the same antigen memory cells will proliferate and mount a secondary response.

Question 32

Interferon

Answer 32

A protein that prevents viral replication and dispersion. Interferons are generated in response to viral infection and are immediately effective against the viral particle. While specific for viruses, they are not directed against any specific viruses and so are considered a nonspcific defense.

Question 33

How and where are blood cells formed?

Answer 33

Formed in bone marrow from same type of precursor, stem cell.

Question 34

Innate immunity:
components

Answer 34

1. Skin
2. Stomach acid / digestive enzymes
3. Phagocytotic cells
4. Blood chemicals

Question 35

Order of innate immune response

Answer 35

Infection → inflammation → macrophages → neutrophils → monocytes

Question 36

Macrophage, neutrophil

Answer 36

Engulf invaders such as bacteria, as well as infected tissue, then die (become pus)

Question 37

Monocytes

Answer 37

Mature into macrophages inside tissue (normally circulate in blood)