L08 T helper and Cytotoxin Cells

Question 1

T helper 1 cells

Answer 1

Derived from Th0 by IL-12 and IFNy
- produce IL-2 and IFNy
Orchestrate a cell mediated immune response

Question 2

Orchestrate a cell mediated immune response :

Answer 2

• up regulate NK cells
• activate Cytotoxic T cells
• activate Macrophages
• up regulate Th1
  -B cells switch to IgG3

Question 3

T helper 2 cells

Answer 3

Derived from Th0 by IL-4
-produce IL-4 and IL-5
Orchestrate humoral immune response

Question 4

Orchestrate humoral immune response:

Answer 4

-Influences Ig isotopes to IgG1, IgG2, IgG4, IgA, IgE
- influence plasma vs. memory B cell differentiation
-eosinophil and basophil recriutment

Question 5

T helper 17 cells

Answer 5

• derived from Th0 by IL-6, TGFB and IL-23
  -produce IL-17 and IL-22
  -involved in autoimmune diseases (RA, psoriasis and MS)
• Anti-fungal
  -Increases the production of neutrophils
  -Involved in gut inflammation

Question 6

T regulatory cells (Tregs)

Answer 6

• derived from Th0 by TGFB
• produce IL-10 and TGFB
  about 10% of CD4+ T cells
  - Natural Tregs
  - Induced Tregs
  -Regulate T cell activation
  -Characterized by CD25+ and Fox P3+

Question 7

Follicular T cells (Tfh)

Answer 7

derived from Th- by IL-6 and IL-21
-produce IL-21
-Located in germinal centers
-CD4+ and PD-1+
-Activate B cells
- Required for germinal Center B cells to undergo somatic hypermutation
-Important for germinal center B cells differentiation into plasma cells and memory cells

Question 8

What influences Th cell polarization?

Answer 8

• Type of antigen presentation
• Live vs. dead antigen
  -Molecular structure of the antigen
  -Route of exposure to antigen
  -HLA type of host - determines response of the individual

Question 9

Th1 stands for

Answer 9

Type 1 immunity

Question 10

Th2 stands for

Answer 10

Type 2 immunity

Question 11

Diseases resolving via Type 1 immune response

Answer 11

Tuberculosis
Chlamydia
Leprosy
Intracellular parasites
HIV

Question 12

Diseases resolving via Type 2 immune responses

Answer 12

Pneumococcal pneumonia
Diphtheria
Meningococcal disease
Helminth (worms)

Question 13

Diseases caused by Type 1 immune responses

Answer 13

Silicosis
Delayed hypersensitivities
Contact hypersensitivities

Question 14

Diseases caused by Type 2 immune responses

Answer 14

Allergies
Asthma
Lupus

Question 15

Activation of CD8+ CTL

Answer 15

Whereas the major function of CD4+ T cell is the production of cytokines, the main function of CTL is cytotoxicity
- aka “Killer T cells” or “T killer cells”, “T cytotoxin cells”
- recognize endogenously produced antigens in association with HLA class I
- Endogenously derived Ag are mostly tumor Ag and Ag from intracellular pathogens (e.g. viruses)

Question 16

The “kiss of death” or “lethal hit”

Answer 16

• it is unidirectional - only the target cell is killed
• after a brief binding episode, the CTL releases from the target moves on to another target cell
  -hours later, the target cells dies
  -A single CTL may deliver multiple (>50?) lethal hits before dying

Question 17

Natural Killer (NK) Cells

Answer 17

• large granular lymphocytes
  -come from a common lymphoid stem cell in the bone marrow
  -CD56+ and CD16+ but no T cell markers
  -no memory- part of the innate response
  -Rather than HLA plus antigen peptide, they recognized “a lack of self” through low-level HLA expression

Question 18

How NK cells recognize foreigness:

Answer 18

-NK possess killer inhibitor receptor (KIRs) that bind HLA class I molecules
- when engaged, killing is inhibited

Question 19

When HLA class I expression is suppressed in a host cell (e.g. during some virus infections or on some tumors)

Answer 19

KIRs are not sufficiently engaged and killing is allowed

Question 20

NK cell killing mechanism:

Answer 20

• Similar to CTL with perforins, granzymes, etc.
• can be positively influenced (up-regulated) by IL-2 and IFN-y
• can produce IFN-y
  -In addition to tumor killing NK are though to be an important first responder during infections with intracellular pathogens - part of innate defense

Question 21

Macrophages cytotoxicity

Answer 21

upon activation with IFN-y alone or in combination with other signals, Macrophages have been shown to be cytotoxic
- Two mechanisms are known

Question 22

Macrophages Cytotoxicity two mechanisms-

Answer 22

TNF-a release and induction of apoptosis

Production of O2 and N2 radicals

Question 23

Antibody-dependent cell-mediated cytotoxicity (ADCC)

Answer 23

Killer cells (K) for ADCC could be either monocytes, B cells, eosinophils, neutrophils or NK cells

Question 24

Which molecules are involved in macrophage cytotoxicity?
1. Fc receptors
2. TNFa
3. IgG
4. Oxygen radicals
5. all of the above

Answer 24

5. All of the above