Role of T lymphocytes

Question 1

What are T cells?

Answer 1

T cells are responsible for cell mediated immunity of the adaptive immunity arm by directly destroying pathogens and assisting other component of the arm which is B cells.

Question 2

What are the two classes of T cells?

Answer 2

Cytotoxic T cells (CD8+)
Helper T cells (CD4+)

Question 3

What is a cytotoxic T Cell?

Answer 3

T lymphocytes with CD8+ receptors
(Cell surface receptor is the T Cell Receptor (TCR)
which only recognises antigens when bound to MHC I)
- Killing

Question 4

What is a Helper T cell?

Answer 4

(CD4+) Helper T cells
T lymphocytes with CD4+ receptors
(Cell surface receptor is the T Cell Receptor (TCR)
which only recognises antigens when bound to MHC II)
- Stimulate B Cells to produce antibody

Question 5

What is the mechanism of a cytotoxic T cell binding to infected cell?

Answer 5

-Cytotoxic T cell binds to infected cell
-Perforin ( mols found in T cell) makes holes in infected cells membrane and enzyme (promotes apoptosis) enters
-infected cell is destroyed

Question 6

MHC complex class 1 ?

Answer 6

Major histocompatibility complex

Any cells with nucleus that could be affected by a virus or by pathogen particularly - is able to express on its surface the MHC1

Responsible for the presentation of an antigen coming from pathogen itself

Question 7

What cells can cytotoxic T cells recognize?

Answer 7

only able to recognize those cells expressed in MHC 1 and the antigen presented

Question 8

What are the four classes of T helper cells?

Answer 8

1 , 2 ,17 and fH

Question 9

How are helper t cells guided to other cells?

Answer 9

guided by specific messengers for e.g. cytokines
for each specific t cell - specific cytokines

Question 10

What is Th1’s defining cytokines, principle target cells, major immune reactions, host defense and role in disease?

Answer 10

IFN- gamma, macrophages, macrophage activation, intracellular pathogens, Autoimmunity; chronic inflammation

Question 11

What is Th2’s defining cytokines, principle target cells, major immune reactions, host defense and role in disease?

Answer 11

IL-4, IL-5,IL-13, Eosinophils, Eosinophil and mast activation; alternative mast activation, Helminths, Allergy

Question 12

What is Th17’s defining cytokines, principle target cells, major immune reactions, host defense and role in disease?

Answer 12

IL-17, IL-22, Neutrophils, Neutrophil recruitment and activation, Extracellular bacteria and fungi, Autoimmunity; inflammation

Question 13

What is TfHs defining cytokines, principle target cells, major immune reactions, host defense and role in disease?

Answer 13

IL-21 (and IFN-gamma or IL-4), B cells, antibody production, extracellular pathogens, autoimmunity

Question 14

Purpose of MHC Class 1?

Answer 14

Class l molecules are a groups of proteins that are found on the surface of virtually all nucleated cells.

Their main function is to bind to specific components of pathogen called peptides or antigens and present them to CD8+ T to trigger cytotoxic response against these pathogens or the cells containing these these pathogens

Note that MHC I present antigens that are obtained from pathogens inside cells and present them only to CD8+.

Question 15

Purpose of MHC Class 2 ?

Answer 15

Unlike MHC Class l molecules, MHC II molecules are a groups of proteins that are found on the surface of only few cells including APCs (Professional Antigen Presenting Cells) which talked about in the first lecture (macrophages for example).

Again they bind to specific components of pathogen called peptides or antigens and present them to CD4+ to trigger immune response against these pathogens or the cells containing these pathogens

Also Note that MHC II present pathogenic antigens that are obtained from pathogens outside the cells and present them only to CD4 not CD8.