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T killers and T helpers Flashcards

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1
Q

What are the subpopulations of T lymphocytes

A

T helpers
T killers
T regulatory

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2
Q

Can any T cell recognise pathogen directly

A

No
They recognise foreign antigen on other cell eg APC with self MHC

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3
Q

Which MHC class does T killers recognise

A

MHC1- for nucleated cells
T killers have co receptor CD8

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4
Q

Which MHC class does T helpers recognise

A

MHC2- immune system cells like b and macroohages
T helpers have co receptoer CD4

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5
Q

Where is MHC1 synthesises

A

ER

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6
Q

What is the origin of antigenic peptides on class I
MHC?

A
  • proteins degraded by proteosomes into peptides (8-10 amino acid chain )
  • TAP (transporter for antigen processing) transfers these peptides to ER
  • MHC1 finds these peptides and binds to them
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7
Q

A cell presenting MHC1 and foreign peptide is not acc a APC.
What is it known as

A

target cell

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8
Q

How are T killers like Natural killers of innate immunity

A

Forces target cell to undergo apoptosis

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9
Q

How does T killers force cell to undergo apoptosis
2 mechanisms

A
  1. They carry FAS ligand which bunds to FAS receptor (death receptor) on target cell
  2. They release perforin( make pores) and granzymes (cuts capases)
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10
Q

How do T killers recognise normal cell with MHC1 or a virus cell

A

Normal cell has fragments of normal proteins

Virus infected cells have unusual peptides on MHC1 and will react

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11
Q

What happens if virus blocks apoptosis

A

More holes are made on the membrane by perforin and induces necrosis

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12
Q

What do T helpers need to recognise

A

They recognise antigen with MHC2 ( not native antigen) on mononuclear phagocytes and b cells

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13
Q

What is the difference between antigen presentation of MHC2 and MHC1

A

MHC1- antigenic peptides are endogenous

MHC2- antigenic peptides exogenous

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14
Q

Antigen presentation of T helpers

A

originate from proteins that are not synthesized in the
antigen-presenting cell but taken from outside by phagocytosis and cut by lysosomal enzymes.

MHC2 are sent to the phagolysosome, bind the antigenic peptides and are
transported to the cell surface for antigen presentation.

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15
Q

Can B cells act as phagocytes

A

They are not phagocytes

But they can have some qualities like endocytosis and intracellular digestion

So they can internalize the antigen bound to their Ig receptor and then present it.

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16
Q

What is important in order to presetn exogenous antogens to T helpers

A

Self peptides cannot settle into the cleft of MHC2
So cleft is occupied by protein INVARIANT CHAIN
Then protease cuts it and makes CLIP

17
Q

What are the subpopulations of T helpers

A

Th1- cell mediated immunity
Th2-humoral immunity

18
Q

Th1 cells assist macrophages in phagocytosis. Why is this needed?

A

Sometimes bacteria and parasites get engulfed by phagocytes but they still survive and reproduce in them :(

Leishmania and toxoplasma does this

Even tho they havent killed pathogen yet, the macrophages will still present their antogens with MHC2.

TH1 ACTIVATES MACROPHAGE BY SECRETING INTERFERON GAMMA

Now macrophage can kill parasite in them :)

19
Q

Interferon gamma released by Th1 is a paracine signalling molecule.
What are they called

A

Cytokines

20
Q

What is thymus independent

A

Only a few antigens can induce antbodies without the help of Th2

NO CLASS SWITCH SO ONLY IGM

Most antigens are thymus-
dependent. B cells specific for them need the help of Th2 cells.

21
Q

Pathogen, TH2 and B cells

A
  1. After binding antigen, the B cell engulfs it, digests it and presents it with MHC-II.
  2. A Th2 cell specific for the same Ag “sees” it and activates the B cell by secreting cytokines.
  3. Cytokines cause the B cell to mature to a plasma cell and secrete antibodies
22
Q

How do u obtain antibody against hapten

A

Hapten binds to a protein bc protein provides epitooes for th2

23
Q

How are t helper cells attacked by HIV

A

HIV binds to t helper CD4 receptor

No adaptive immunity

Causes AIDS

24
Q

What is TYPE IV hypersensitivty: why is it termed delayed?

A

Occurs only 24-72 hours after exposure

Delay due to time required for T cell
differentiation, cytokine +chemokine secretion,
and accumulation of leukocytes at site.

25
Q

what is type 4 hypersensitivity based on

A

Th1 cells
- T killers / activated macrophages

type IV involves
antigen-specific effector T cells. (while others mediated by antibodies)

26
Q

Examples of type 4 hypersensitivity

A
  • Tuberculin reaction
  • Contact dermatitis,
  • Transplant rejection,

Biology (36 decks)

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