Lecture 12

Question 1

What happens during cellular immunity?

Answer 1

• produces T lymphocytes to recognize antigenic peptides processed by phagocytic cells

Question 2

What are T cell receptors?

Answer 2

on the T cell surface to contact antigens
- causes the T cells to secrete cytokines instead of antibodies

Question 3

What happens during cellular immunity?

Answer 3

attacks antigens that have already entered cells
- like viruses

Question 4

What happens during humoral immunity?

Answer 4

fights invaders and threats outside cells
- extracellular bacteria and toxins
- viruses before they enter a host cell

Question 5

How do T cells combat intracellular pathogens?

Answer 5

• thymic selection eliminates immature T cells
• migrate from the thymus to lymphoid tissues
• attach to antigens via t-cell receptors

Question 6

Where are T cells mature?

Answer 6

thymus

Question 7

What is the cellular immunity response process?

Answer 7

pathogens enter the gastrointestinal tract and pass through microfold cells (M cells) in Peyer’s patches
- transfers antigens to lymphocytes and antigen-presenting cells (APCs)

Question 8

What are examples of antigen-presenting cells? (APCs)

Answer 8

• dendritic cells
• macrophages

Question 9

Where are dendritic cells found? What is their function?

Answer 9

• found in skin, genital tract, lymph nodes, spleen, thymus, blood
• engulfs and degrades microbes and display them to T cells

Question 10

What is the function of macrophages? How are they activated?

Answer 10

• migrate to lymph tissue to present antigen to T cells
• activated by cytokines or the ingestion of antigenic material

Question 11

What are the 2 clusters of differentiation? What’s in them? What do they do?

Answer 11

• CD4+ = T helper cells that bind MHC class II molecules on B cells and APCs
  = cytokine signaling with B cells; interact directly with antigens
• CD8+ = cytotoxic T lymphocytes that bind MHC class I molecules

Question 12

How do T helper cells work?

Answer 12

t-cell receptor on the cell recognize and bind to the antigen fragment and MHC class II on antigen-producing cell
- secretes costimulatory molecule to activate T helper cell

Question 13

What does the T helper cell produce?

Answer 13

cytokines

Question 14

What do the cytokines differentiate into?

Answer 14

• T helper 1 cells
• T helper 2 cells
• T helper 17 cells
• memory cells

Question 15

What do T helper 17 cells produce? What does it lead to?

Answer 15

IL-17
- contributes to inflammation

Question 16

What do T helper 1 cells produce? What does it lead to?

Answer 16

IFN-gamma
- activates macrophages
- enhances complement
- stimulates antibody production that promotes phagocytosis

Question 17

What do T helper 2 cells produce? What does it lead to?

Answer 17

IL-4 cytokine
- activates B cells to produce IgE
- activates eosinophils

Question 18

What are T regulatory cells?

Answer 18

• subset of CD4+ cells
• carry additional CD25 molecule

Question 19

What is the function of T regulatory cells?

Answer 19

suppresses T cells against self
- protects intestinal bacteria required for digestion
- protects fetus

Question 20

How do cytotoxic T lymphocytes formed? How do they work?

Answer 20

precursor T cytotoxic cells are activated to become cytotoxic T lymphocytes (CTLs) with the help of T-helper cell and costimulatory signals
- CTLs recognize and kill self-cells altered by infection (self-cells carry endogenous antigens on MHC class I molecules)
- CTLs release perforin and granzymes that induce apoptosis in the infected cell

Question 21

Why does apoptosis happen?

Answer 21

• prevents the spread of infectious viruses into other cells
• cells cut their genome into fragments, causing the membranes to bulge outward via blebbing

Question 22

What is the function of natural killer cells?

Answer 22

• granular leukocytes destroy cells that don’t express MHC class I self-antigens
• kill virus-infected and tumor cells and attack parasites
• not always stimulated by an antigen
• form pores in the target cell, leading to lysis or apoptosis

Question 23

What happens to protozoans and helminths since they’re too big to be pahgocytized?

Answer 23

• target cell is coated with antibodies
• immune system cells attach to Fc regions of antibodies
• target cell is lysed by chemicals secreted by the immune system cell

Question 24

What happens during the secondary response after the second exposure to an antigen?

Answer 24

• class switching where initial IgM response shifts to IgG, IgE, IgA
• memory cell produced in response to the initial exposure are now activated by the secondary exposure

Question 25

What is antibody titer?

Answer 25

relative amount of antibody in the serum
- reflects intensity of humoral response

Question 26

What is naturally acquired active immunity?

Answer 26

antigens enter the body naturally
- body induces antibodies and specialized lymphocytes

Question 27

What does naturally acquired active immunity result from?

Answer 27

infection

Question 28

What is naturally acquired passive immunity?

Answer 28

antibodies pass from mother to fetus through the placenta or to infant through the mother’s milk

Question 29

What is artifically acquired active immunity?

Answer 29

antigens are introduced in vaccines
- body produces antibodies and specialized lymphocytes

Question 30

What are artificially acquired passive immunity?

Answer 30

preformed antibodies in immune serum are introduced by injection