T Cells, HIV

Question 1

Ratio of T cell in lymphocyte population

Answer 1

Two-third of circulating lymphocytes

Question 2

Origin and Maturation of T cells

Answer 2

Origin: Bone marrow

Maturation: Thymus gland

Question 3

Origin and maturation:

T cells VS B cells

Answer 3

B cells are manufactured and matured in bone marrow

T cells are manufactured in bone marrow BUT maturation takes place in thymus gland

Question 4

Process of maturation of T cells

Answer 4

• Auto-reactive cells are removed
• Then they develop into either T helper cells OR cytotoxic T cells

Question 5

Which class of HLA is recognised by helper T cell and cytotoxic T cell?

Answer 5

• Cytotoxic T cell recognises class-I HLA
• T-helper cell recognises class-II HLA

Question 6

Which clusters of surface antigen (= CD: Clusters of Differentiation) are expressed by T cells?

Answer 6

All T cells express CD3

• CD4 is conserved among helper-T cells (CD4+ helper-T cells)
• CD8 is conserved smong cytotoxic T cells (CD8+ cytotoxic T cells)

Question 7

Can we distinguish T cells under light microscopy?

Answer 7

NO

All T cells look much the same under light microscopy

Question 8

Investigation to distinguish T cells

Answer 8

Flow cytometry

Question 9

How do we distinguish T cells by flow cytometry?

Answer 9

We identify clusters of surface antigen ( = Clusters of differentiation = CD)

All T cells express CD3

Only T helper cells express CD4

Only cytotoxic T cells express CD8

Question 10

Which CD (Clusters of differentiation) is “Common” to be expressed by CD4+ helper-T cells and CD8+ cytotoxic T cells?

Answer 10

CD3

Question 11

T-helper cells: Common subtypes

Answer 11

• Th1
• Th2
• Th17

Question 12

The most aggressive phenotype of T-helper cell

Answer 12

Th-1

Question 13

The most tolerant phenotype of T-helper cell

Answer 13

Th-2

Question 14

Which type of T helper cell has a prominent inflammatory response?

Answer 14

Th-1

Question 15

What can trigger type-1 T-helper cells (Th-1)?

Answer 15

Cytokines (such as IFN: Interferon)

>>> resulting in a hostile environment for pathogens

Question 16

What can trigger type-2 T-helper cells (Th-2)?

Answer 16

Cytokines, such as: Interleukin-10 (IL-10)

Question 17

Th-2: Functions

Answer 17

• Associated with “humoral response”
• Drives antibody class switching

Question 18

Give an example when Th-2 predominates

Answer 18

Pregnancy

Question 19

Predominant subtype of T-helper cells in Pregnancy

Answer 19

Th-2

Question 20

Recent sub-type of T-helper cell

Answer 20

Th-17 (T-helper cell type 17)

Question 21

What does activate Th-17?

Answer 21

IL-17

Question 22

Which type of T cells are current subject of pharmaceutical trials across a borad range of diseases?

Answer 22

Th-17 (along with its activator IL-17)

Question 23

Cell that provides immune system a “window” into other cells

Answer 23

T lymphocytes

Question 24

Cell that is especially imporant defence against intracellular pathogen

Answer 24

T cells

Question 25

**Association of T cells with autoimmunity**

Answer 25

**Normal function of T cell is essential to prevent autoimmunity**

Question 26

**What is genetic predictor of autoimmune disease & example?**

Answer 26

**Genetic predictor is the genetic code for HLA on chromosome 6** **Example:** * **HLA-DR4 \>\>\> Rheumatoid Arthritis** * **HLA-Cw6 \>\>\> Psoriasis**

Question 27

**Name a T-cell deficiency disease**

Answer 27

**HIV AIDS**

Question 28

**Main effect of HIV on T cells**

Answer 28

**HIV causes progressive depletion of CD4 T-helper cell population**

Question 29

**Which type of T cell is affected/depleted by HIV?**

Answer 29

**CD4 T cells**

Question 30

**How does HIV deplete CD4 T cells?**

Answer 30

* **IL-2 (a cytokine) is central to T cell proliferation** * **HIV supresses IL-2 \>\>\> induced T-cell deficiency state**

Question 31

**Which type of cytokine is supressed by HIV?**

Answer 31

**IL-2 (interleukin-2)**

Question 32

**Similarity of "mechanism" between "HIV infection" and "Ciclosporin or Tacrolimus drugs"**

Answer 32

**Both inhibit IL-2**

Question 33

**Similarity of "side-effects" between "HIV infection" and "Ciclosporin or Tacrolimus drugs"**

Answer 33

**Both cause same pattern of opportunistic infection (as both inhibit IL-2)** * **TB (Tuberculosis)** * **Pneumocystis Jerovecii** * **Disseminated viral disease**

Question 34

**"Opportunistic infections" that are common between "HIV infection" and "Ciclosporin or Tacrolimus drugs therapy"**

Answer 34

* **TB (Tuberculosis)** * **Pneumocystis Jerovecii** * **Disseminated viral disease**

Question 35

**Number of 'specific' receptor on lymphocytes (B cell or T cells)**

Answer 35

**Each individual lymphocyte expresses a "single type of receptor" with "unique specificity" (except dual specificity T cells)**

Question 36

**Type of receptor on B cell and T cell**

Answer 36

* **B cell receptor \>\> memrane bound immunoglobulin (IgM monomer or IgD isotype) \>\> recognises particular Ag** * **T cell receptor \>\> TCR (T cell receptor) complex: a heterodimer \>\> recognises peptide fragments (presented by MHC molecules)**

Question 37

**Where is the 'antigen specificity' of B cell and T cell generated?**

Answer 37

* **For B cells \>\> bone marrow** * **For T cells \>\> Thymus**

Question 38

**When is the 'antigen specificity' of B cell and T cell generated?**

Answer 38

**During development (at maturation phase)**

Question 39

**How is the 'antigen specificity' of B cell and T cell generated?**

Answer 39

**By recombination of gene segments encoding the variable domains (antigen recognition domains) of immune receptors** * **These gene recombinations are random** * **Maturing lymphocytes that express autoreactive receptors \>\>\> then deleted or rendered anergic**

Question 40

**Are all autoreactive lymphocytes deleted duting development?**

Answer 40

**NO** **Not all autoreactive lymphocytes are deleted during development.** **In the case of T lymphocytes,** * **NOT all proteins are expressed in the thymus** **AND the proteins that are present only in the periphery OR at certain stages of development \>\>\> will encounter mature T cells that can respond to them.** **\>\>\> Thus, autoreactive T cells exist in the periphery** (and other mechanisms are responsible for the protection of the body against autoimmunity)