Lecture 19 Immunology and Pathogenicity and Infection

Question 1

What is the major mechanism that involves the rearrangement of antibody gene segments

Answer 1

VDJ Recombination

Question 2

Describe VDJ Recombination

Answer 2

• Recombination Activating Gene (RAG) enzymes
• Activated in B cells
• Randomly cut and paste gene segments.

Question 3

When does Random Rearrangement of antibody gene segments occur?

Answer 3

• As B cells develop in the bone marrow

- Early in embryonic life, before infection

Question 4

What is tolerance?

Answer 4

Removal of self-reactive B cells

Largely occurs in bone marrow

Question 5

What happens to the B cell upon infection?

Answer 5

• antigen “selects” B cell with antibody that matches it.

- B cell proliferates, forming clone of identical cells, each with antibody for the antigen.

Question 6

Secondary Response to antigen.

Answer 6

Activation of memory B cell strong response

- Basis of Immunization

Question 7

Humoral

Answer 7

B cell and production of antibodies

- extracellular pathogens

Question 8

Cell - Mediated

Answer 8

• intracellular pathogens

- T cell

Question 9

T cells

Answer 9

• Originate in bone marrow, mature in thymus

- Activated when their receptors bind antigens presented by other cells

Question 10

Helper T cells

Answer 10

-Make cytokines, activate B cells, macrophages, or other T cells

Question 11

Cytotoxic T cells

Answer 11

• kill cells expressing foreign antigens using

Perforins and Granzymes (enzymes)

Question 12

What are the enzymes that Cytotoxic T cells use and what is there function?

Answer 12

Perforins - form pores

Granzymes - induce apoptosis

Question 13

Describe Cluster of Differentiation (CD) molecules and the common examples.

Answer 13

• membrane proteins on immune cells
• Call also be used to determine cell’s identity
• Helper T cells - CD4
• Cytotoxic T cells - CD8

Question 14

T - Cell Receptors (TCRs)

Answer 14

• Receptors bind antigens (usually peptides) presented to the, by other cells
• Only when presented with a MHC molecule
• TCRs are expressed from gene segments rearranged in thymus.

Question 15

Human Leukocyte Antigen (HLA)

Answer 15

• Humans have 2 sets of MHC genes
• One from each parent both are expressed

-Closer 2 people related, more similar their HLAs, important in donor selection for tissue, bone marrow and organ transplant- HLA Typing.

Question 16

Class 1 MHC

Answer 16

• on all nucleated cells
• present peptides that originate in cytoplasm from intracellular pathogens
• Present peptides to CD8+ Cytotoxic T cells

Question 17

Class 2 MHC

Answer 17

• only on antigen-presenting cells (dendritic cells, macrophages, B cells)
• Present peptides from extracellular pathogens, taken up by phagocytosis
• Present peptides to CD4+ Helper T Cells

Question 18

What is a Pathogen

Answer 18

• Organism that produces disease

Question 19

Opportunistic Pathogen

Answer 19

-Infects host with weakened immune system

Question 20

Carrier

Answer 20

-Infected individual potential source of infection (no observable symptoms)

Question 21

Zoonoses

Answer 21

-diseases transmitted to humans from animals

Question 22

Vector

Answer 22

-Organisms (usually insects) that transmit disease to humans - mosquitoes, ticks, fleas

Question 23

Pathogenicity

Answer 23

ability to produce disease

Question 24

Virulence

Answer 24

degree of pathogenicity

Question 25

Latency

Answer 25

Pathogen stops reproducing, dormant, can become active again

Question 26

How do we measure virulence?

Answer 26

• Lethal Dose 50 (LD50)
• # to kill 50% of hosts
• Infectious Dose 50 (ID50)
• # of pathogens required to cause clinical disease in 50% of inoculated hosts

Question 27

How do we study pathogens, Virulence and Pathogenicity.?

Answer 27

Model Systems - animal models, cell culture

Human Studies - Clinical Trials, Case studies

Epidemiology - Examine incidence, distribution, control of disease