Lecture 17 10/23/23

Question 1

What are the general characteristics of immunity to bacteria?

Answer 1

-mediated by all mechanisms (innate, antibody-mediated, cell mediated)
-antibodies most significant
-cell-mediated need to control intracellular bacteria

Question 2

Which parts of innate immunity are important for bacterial immunity?

Answer 2

-PRRs
-complement
-innate lymphoid cells (ILC3s)

Question 3

What happens when PRRs recognize bacteria?

Answer 3

-cytokine release
-complement activation
-inflammation
-phagocytosis

Question 4

Which TLR provides chickens with resistance to Salmonella?

Answer 4

TLR4

Question 5

Which TLR provides foals with resistance to Rhodococcus equi?

Answer 5

TLR2

Question 6

How does complement provide immunity against bacteria?

Answer 6

-pore formation/lysis of bacterial cells
-recruitment of other immune cells

Question 7

Which substances are able to activate TLR4 on horse platelets?

Answer 7

-bacterial LPS from E. coli
-lipoteichoic acid from S. aureus

Question 8

What substances are released by horse platelets in response to bacteria?

Answer 8

-antibacterial peptides
-reactive oxygen species

Question 9

How do horse platelets interact with neutrophils?

Answer 9

they bind to neutrophils to form aggregates and enhance neutrophil activity

Question 10

What are the characteristics of ILC3s?

Answer 10

-produce IL-22 in response to IL-23 stimulation
-central role in mucosal immunity
-resist extracellular bact. and fungi

Question 11

How does IL-22 act on enterocytes?

Answer 11

stimulates the cells to produce antimicrobial proteins and protect the GI tract

Question 12

What are the five mechanisms used by the adaptive immune system to combat bacterial infections?

Answer 12

-neutralization of toxins/enzymes via antibody
-killing of bact. through classical complement pathway
-opsonization via antibodies and complement resulting in phagocytosis
-destruction of intracellular bact. by macrophages
-direct killing of bact. by cytotoxic T cells

Question 13

What is important about infections caused by toxigenic species (such as Clostridia or B. antracis)?

Answer 13

invading pathogen must be eliminated AND toxin must be neutralized

Question 14

When does neutralization occur?

Answer 14

when antibodies prevent toxin from binding to its target receptors

Question 15

Which proteins can opsonize bacteria?

Answer 15

-antibodies
-C3b

Question 16

How are intracellular bacteria targeted?

Answer 16

-Th1 cells produce IFN-gamma
-IFN-gamma activates macrophages to destroy intracellular bact. in phagosomes

Question 17

What is the body’s last line of defense?

Answer 17

cytotoxic immune cells

Question 18

Which bacterial species are able to produce IgA proteases?

Answer 18

-Streptococcus
-Neisseria
-haemophilus

Question 19

What do IgA proteases do?

Answer 19

break down secretory IgA antibodies (prevent mucosal immunity)

Question 20

Which bacterial species uses leukotoxins?

Answer 20

Staphylococcus

Question 21

What do leukotoxins do?

Answer 21

form pores in host immune cell membranes, leading to apoptosis

Question 22

How does Staph. aureus utilize protein A?

Answer 22

-protein A on cell surface binds to Fc region of antibody
-prevents antibody from inducing phagocytosis

Question 23

What are the immune evasion mechanisms of Borrelia (which causes lyme)?

Answer 23

-inhibition of MAC assembly/pore formation
-changing surface proteins
-spiral movement/evasion of immune cells