CH16- host immune response to bacterial infections

Question 1

Major cell wall anitgens of bacteria

Answer 1

Gram positive and gram negative

Question 2

gram positive had what in it?

Answer 2

peptidoglycan, teichoic acid

Question 3

gram negative has what in it?

Answer 3

LPS, Somatic (O) antigen), Toxic component Lipid A

Question 4

what happens when LPS directly activates B cells?

Answer 4

To produce IgM antibodies - potent activator of macrophages

Question 5

What are some other antigens?

Answer 5

Capsular antigen (K- antigen), Fimbra antigen, Flagellar antigen, Exotoxins

Question 6

What is Capsular antigen?

Answer 6

K antigen like LPS directly activates B cells to produce antibodies IgM

Question 7

What does Fibra antigen do?

Answer 7

Stop attatchement. messes with the fimbriae

Question 8

What does flagellar antigen do?

Answer 8

H antigen. antibodies against flagella

Question 9

What are exotoxins?

Answer 9

Proteins that gram Positive and gram negative bacteria and causes diseases

Question 10

what are toxoids

Answer 10

derived from exotoxins and induce the formation of antitoxins in the host.

Question 11

Can extracellular bacteria live long?

Answer 11

cant live long in phagocytes!

Question 12

Where do extracellular bacteria replicate?

Answer 12

outside the host ( blood Ct, intestinal lumen) attach epithelial surfaces

Question 13

Extracellular bacteria causes disease by producing?

Answer 13

endotoxins and exotoxins

Question 14

In innate immunity what do we do with extracellular bacteria?

Answer 14

Phagocytic cells ( neutrophils number 1) eliminate bacteria via phagocytes
complement activation on bacterial surface
Inflammation

Question 15

IN innate immunity what does the complement activation do?

Answer 15

Complement mediated lysis of bacteria ( gram - negative bacteria)
Opsonization and phagocytosis ( C3b, iC3b, C4b)

Question 16

What are our inflammation factors in extracellular bacteria?

Answer 16

C5a, C3a, C4a ( induces local mast cell (histamine)

Question 17

Adaptive immunity of Extracellular parasites consist of what?

Answer 17

Neutralization of bacterial toxins
Opsonization ( IgG) and Fcy receptor -mediated phagocytes
Complementactivation via the classic path way. IgG IgM
Prevention of bacterial adhearence to mucosal surfaces

Question 18

What is immunity to intracellular bacteria? what does it do?

Answer 18

Cell mediated-

Question 19

WHere does intracellular bacteria replicate?

Answer 19

inside host cells - macrophages

Question 20

Antibodies produced during the phase merely indicate exposure to antigen but doesn’t mean?

Answer 20

they have protective immunity!

Question 21

Innate immunity what do your macrophages secrete?

Answer 21

IL-12 this activates Natural Killer cells

Question 22

What do Activated NK cells turn on?

Answer 22

IFN-gamma ( this activates macrophages)

Question 23

Adaptive immunity for intracellular bacteria is principally humoral mediated. True or false?

Answer 23

FALSE cell mediated

Question 24

for intracellular cell mediated response what cells are involved and what do they do?

Answer 24

CD4 T helper cells respond to MHC class II peptide antigens that come from bacteria.
IL-12 is secreted from macrophages.
The Activated CD4 cell expresses CD40L and secretes IFN gamma, both of which activate macrophages, enhancing the killing of the microbes in the phagolysosoomes.

Question 25

What are bacterial superantigens?

Answer 25

they are soluble bacteria antigens

Question 26

Where do superantigens bind?

Answer 26

V beta domain on the TCR ( CDR4)
Bind to alpha chain of class II MHC on APCs

Question 27

what does crosss linkage of Tcell receptor and MHC class II induce?

Answer 27

T cell activation and proliferation

Question 28

If there is an over production Th Cytokines what can happen and what does it over produce?

Answer 28

Over produced TNF-alpha leads to system toxicity.

Question 29

How can the bacteria evade host immune responses?

Answer 29

1. ) Killing the phagocyte ( secrete leukocidin)
2. ) inhibit membrane attachment ( capsule) (sialic acid which resist C3b) ( M protein alters cell surface membrane)
3. ) inhibit fusion of lysosomal granules and phagosome
4. ) resistance to killing and digestion (cell wall lipids)
5. )escape from the phagosome ( Lysterlysine O)
6. ) bacteria contains proteases
7. ) antigenic variation
8. ) gram positive bacteria ( resistant to complement)

Question 30

What immunity goes with fungal infections?

Answer 30

innate immunity

Question 31

Who mediates this immunity?

Answer 31

macrophages and neutrophils

Question 32

what secretes IFN-gamma?

Answer 32

NK cells, Tcells, CD8

Question 33

What does IFN-gamma do?

Answer 33

go to macrophages and lyse them.

Question 34

Antibodies produced in response to fungal infections are useful in what?

Answer 34

Serologic diagnosis