5 - Adaptive immunity (Cell mediated immune responses)

Question 1

Why are there more CD8 cells than CD4 cells during an infection

Answer 1

Because CD8 cells kill the infected cell directly, whereas CD4 cells produce cytokines which travel throughout the body so less is needed

Question 2

Thymocyte

Answer 2

T cells originating in bone marrow, go to thymus to differentiate.

Question 3

T cell negative selection

Answer 3

Death by neglect (no recognition of MHC peptide) or strong recognition of self antigen

Question 4

T cell positive selection

Answer 4

T cell differentiates into CD8 or CD4 in the medulla of the thymus

Question 5

Immunologic tolerance

Answer 5

lack of response to antigens that is induced by exposure of lymphocytes to these antigens

Question 6

What is the underlying cause of autoimmune diseases

Answer 6

Failure of self tolerance

Question 7

Principal mechanisms of central tolerance in T cells

Answer 7

Death of immature T cells (negative selection) and the generation of CD4 + regulatory T cells

Question 8

What does peripheral tolerance lead to

Answer 8

Functional inactivation (anergy) or death, or when the self reactive lymphocytes are suppressed by regulatory T cells

Question 9

Where does central tolerance occur

Answer 9

Generative lymphoid organs (bone marrow and thymus)

Question 10

Central tolerance

Answer 10

Lymphocytes with receptors specific for self-antigens are deleted at an early stage in development.

Question 11

Peripheral tolerance

Answer 11

Peripheral tissues

Question 12

Two types of TCR

Answer 12

αβ TCRs and γδ TCRs

Question 13

Different regions of a TCR

Answer 13

• Antigen recognising domains = Variable (V) regions
• Conserved portions = constant (C) regions

Question 14

function of invariant membrane proteins

Answer 14

• Deliver intracellular signals following antigen
  recognition
• Associated with antigen receptor chains

Question 15

Subsets of CD4 helper T cells

Answer 15

Th1, Th2, Th17, Tfh and Treg

Question 16

Th17 cells

Answer 16

develop in response to extracellular bacterial
and fungal infections and induce inflammatory reactions that destroy these organisms

Question 17

Regulatory T cells

Answer 17

Suppress immune responses

Question 18

What causes Th0 cells to differentiate into Th1

Answer 18

DCs produce IFN-γ and IL-12

Question 19

Th1

Answer 19

Acting through CD40 ligand and IFN- γ , increase the ability of macrophages to kill phagocytosed microbes

Question 20

Response of macrophages to Th1 cells

Answer 20

• Killing of phagocytosed bacteria
• Increased expression of MHC and costimulators
• Secretion of cytokines (TNF, IL-1, IL-12, chemokines)

Question 20

End result of Th1 cells

Answer 20

• Killing of phagocytosed bacteria
• Increased expression of MHC

Question 21

IFN- γ

Answer 21

• Produced by Th1 cells
• contribute to the recruitment of monocytes and granulocytes
• activate the antimicrobial activity of macrophages
• phagosome maturation
• production of reactive nitrogen intermediates
• antigen presentation

Question 22

CD4 T cells deficiency (e.g. HIV+)

Answer 22

Increases susceptibility to both primary and reactivation tuberculosis as T cells participate in granuloma formation

Question 23

Granuloma

Answer 23

hallmark of TB

Question 24

What causes Th0 cells to differentiate into Th2

Answer 24

DCs produce IL-4

Question 25

Th2

Answer 25

• Acting through IL-4, IL-5 and IL-13, stimulate antibody responses and defend against helminth parasites
• Involved in allergic reactions to environmental antigens

Question 26

End result of Th2 cells

Answer 26

• Alternative macrophage activation (tissue repair) (IL-4 and IL-13)
• Eosinophil activation (IL-5)
• Intestinal mucus secretion and peristalsis (IL-4 and IL-13)
• Mast cell degranulation (IL-4)
• Antibody production (IL-4)

Question 27

Cytotoxic T lymphocytes (CTL)

Answer 27

Uses perforin and
granzymes to destroy infected cells

Question 28

CD8+ T cells

Answer 28

Activated upon binding to
non-self antigen presented by DC in the context of MHC-I

Question 29

Perforin

Answer 29

• Disrupts the integrity of the target cell plasma and endosomal membrane
• Facilitates the delivery of granzymes into the cytosol

Question 30

Granzymes

Answer 30

Major function is to induce
apoptosis

Question 31

CD4+ and CD8+ T cell cooperation

Answer 31

• CD4 + T cells recognise antigens derived from the vesicular microbes and activate the macrophage to kill the microbes in the vesicles
• CD8 + T cells recognise antigens derived from the cytosolic bacteria and are needed to kill the infected
  cell, thus eliminating the reservoir of infection

Question 32

TO DO:

Answer 32

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