Immune Response (to Bacteria)

Question 1

What are the characteristics of the innate immune response?

Answer 1

• Immediate, First line of defense
• Non-specific for individual pathogen
• Can combat a wide range of pathogens

Question 2

What are the characteristics of the adaptive immune response?

Answer 2

• Takes longer than innate IR
• Production of bacteria-specific antibodies
• Responsible for immunological memory (lifetime immunity)

Question 3

What are some physical barriers to infection (pre-innate IR)?

Answer 3

• Eye (blinking, lysozyme)
• Skin (structural barrier, sweat, lactic acid)
• Resp. tract (coughing, mucus, cilliary action)
• GI tract (stomach acidity, peristalsis)
• Urogenital tract (urine acidity, lavaging action of urine)

Question 4

What are some innate immunity WBCs? How do they work?

Answer 4

• Phagocytotic WBCs (neutrophils, macrophages)
• Recognize pathogen-associated molecular patters (PAMPs) on pathogen (not on self molecules)
• > then kill with degrading enzymes and toxic chemicals

Question 5

What is the complement immune system?

Answer 5

• A system used to ID bacteria using 30 different plasma proteins (from liver) which produce fragments that coat the bacteria
• > Phagocytosis or Inflammation induction
• Activated by bacterial infection

Question 6

What are the three pathways in the complement system?

Answer 6

Classical, Alternative, Lectin

Question 7

What is the classical complement pathway?

Answer 7

• Anti-body triggered pathway
• C1q protein interacts with pathogen surface or ABs attached to pathogen -> C3 convertase activation -> C3 cleavage (C3a, C3b fm.)

Question 8

What is the alternative complement pathway?

Answer 8

• Activated by presence of antigen alone

- C3 undergoes spontaneous hydrolysis -> deposition of C3 convertase to microbial surface -> C3 cleaved (C3a, C3b)

Question 9

What is the lectin complement pathway?

Answer 9

• Activated by mannose-binding lectins (MBLs) that recognize/bind antigen carbohydrates
• > C3 convertase -> C3 cleaved (C3a, C3b)

Question 10

How does C3 cleavage lead to immune response? What are the immune responses from the complement pathway?

Answer 10

• C3a and C5a recruit phagocytes and promote inflammation (messengers)
• C3b deposited on pathogen surface for recognition and engulfment by phagocytes (marking of target pathogen)
• Fm of membrane-attack complex (MACs) -> cell membrane interruption and cell lysis

Question 11

What are the key players in adaptive immunity?

Answer 11

B cells, T cells, Dendritic cells

Question 12

Where is the adaptive immune response activated?

Answer 12

Secondary lymphoid tissue (tonsils, spleen, lymphnodes, etc.)

Question 13

How do dendritic cells lead to effector T-cell formation?

Answer 13

• Dendritic cells bind to pathogen
• > Engulf pathogen and travel to lymphoid tissue via lymphatic vessels
• > T-cells that recognize pathogen antigens on MHC bind and divide (proliferation of effector T-cells to fight infection)

Question 14

What are T-cells called that don’t recognize the pathogen antigens?

Answer 14

Naive T-cells

Question 15

Process from pathogen to antigen display?

Answer 15

• Dendritic cell engulfs pathogen
• > broken down into protein fragments (in cytosol or lysosomes)
• > carried to MHC I or MHC II (depending on type of pathogen)

Question 16

What’s the difference between MHC I and MHC II?

Answer 16

• MHC I: intracellular pathogens (degraded in cytosol)

- MHC II: extracellular pathogens (degraded in lysosomes)

Question 17

What’re the different types of T-cells that bind to MHC I and MHC II respectively? What cell-surface molecule do they carry?

Answer 17

RULE OF 8!
Cytotoxic T-cell: intracellular pathogen, carry CD8, bind to MHC I, eliminate pathogen
Helper T-cell: extracellular pathogen, carry CD4, bind to MHC II, increase phagocytosis activity, help B cells make ABs

Question 18

What are the two types of immune responses?

Answer 18

Innate and Adaptive