Lecture 12: Adaptive immunity - Clonal Selection of Lymphcytes

Question 1

What are the two branches of the immune response?

Answer 1

Humoral Branch and Cell-Mediated Branch

Humoral Branch involves B cells and antibodies; Cell-Mediated Branch involves T cells.

Question 2

What does humoral immunity primarily involve?

Answer 2

B cells and antibodies

It is a part of acquired immunity.

Question 3

What is innate immunity?

Answer 3

Nonspecific immunity

Nonspecific immunity ## Footnote It includes physical barriers, chemical barriers, molecular defenses, cellular defenses, inflammation, and fever.

Question 4

What are lymphocytes?

Answer 4

T and B cells

hey are antigen-specific and randomly generated.

Question 5

How many different B and T cells can exist in the human body?

Answer 5

10^12 to 10^16 different B and T cells

Question 6

What do T cells have that B cells do not?

Answer 6

T cell receptors (TCR)

cells have B cell receptors (BCR).

Question 7

Define antigen.

Answer 7

A substance that the body sees as foreign or non-self, and to which it mounts an immune response.

Question 8

What are the most common types of antigens?

Answer 8

Proteins

Some antigens can also be polysaccharides, glycoproteins, or nucleoproteins.

Question 9

What are epitopes?

Answer 9

Short amino acid sequences recognized by antibodies and T cells (8-20 amino acids).

Question 10

What is the primary immune response?

Answer 10

The response to the first exposure to an antigen, taking 7-10 days to detect antibodies.

Question 11

What is the secondary immune response?

Answer 11

The response to a second exposure to the same antigen, occurring within hours to days.

Answer 12

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Question 13

What are CD4 T cells also known as?

Answer 13

T-helper cells

Question 14

How do naïve CD4 T cells become T-helper cells?

Answer 14

They recognize their epitope and receive a cytokine signal.

Question 15

What do T-helper cells do?

Answer 15

Secrete cytokines that direct other immune cells.

Question 16

What is the role of professional antigen presenting cells (APCs)?

Answer 16

Express class II MHC and present epitopes to naïve CD4 T cells.

Question 17

What happens to most effector T-helper cells after infection is cleared?

Answer 17

They die, but some become memory T cells.

Question 18

How do CD8 T cells become cytotoxic T lymphocytes (CTL)?

Answer 18

They must see their specific epitope presented on Class I MHC and receive a cytokine signal.

Question 19

What do CTL cells do?

Answer 19

Release cytotoxins onto infected target cells.

Question 20

What is the role of naïve B cells in humoral immunity?

Answer 20

They recognize and bind to epitopes on antigens using the BCR.

Question 21

What happens to B cells during the primary immune response?

Answer 21

They switch from making IgM to a different isotype as needed.

Question 22

What is the memory response in B cells?

Answer 22

A faster response (2-3 days) due to memory B cells not needing T cell help.

Question 23

True or False: Memory T cells need as many signals from professional APCs as naïve T cells to get activated.

Answer 23

False

Question 24

Which virus causes non-specific overproliferation of B & T cells?

Answer 24

Epstein Barr virus (mononucleosis).

Question 25

Which enzyme cleaves IgA, and which bacterium produces it?

Answer 25

IgA protease, produced by Streptococcus pyogenes (strep throat).

Question 26

What do Protein A and Protein G do in bacterial evasion?

Answer 26

Bacteria produce Protein A or Protein G, which flips IgA or IgG around, preventing antibody function (no neutralization, opsonization, or complement fixation).

Question 27

Which viruses are known to hide antigens?

Answer 27

HSV and measles.

Question 28

Name a virus, a bacterium, and a protozoan that change their antigens.

Answer 28

Virus: Influenza. Bacterium: Gonococci. Protozoan: Trypanosomes (sleeping sickness).

Question 29

Which pathogens can reproduce in white blood cells (WBC)?

Answer 29

M. tuberculosis, HIV, and many others.

Question 30

How does HIV affect CD4 T cells?

Answer 30

HIV kills CD4 T cells, leading to no T helper cells.

Question 31

What is the result of no activation of B cells due to HIV?

Answer 31

No antibody production, no neutralization of toxins, viruses, or other microbes, decreased opsonization (still have complement), and no complement fixation.

Question 32

What happens due to no activation of cytotoxic T lymphocytes (CTL) because of HIV?

Answer 32

No killing of infected cells, and no killing of tumor cells.

Question 33

What are the overall consequences of microbial evasion of adaptive immunity, particularly in the case of HIV?

Answer 33

Opportunistic infections and increased risk of cancer.