Lecture 11 - Linking Innate & Adaptive Immunity (T-Cells and MHC - The Basics)

Question 1

True or False?:

Many of the processes of the immune system overlap over time, can change locations, and influence each other.

Answer 1

True

Question 2

What is required for T-cells to recognize peptide fragments of Ag?

Answer 2

For T-cells to recognize peptide fragements of Ag, they must be bound to self molecules of the MHC.

Question 3

Where are peptide-MHC complexes found?

Answer 3

Peptide-MHC complexes are expressed on the plasma membrane of self APCs.

Question 4

True or False?:

T-cells are made in the thymus.

Answer 4

False

T-cells mature in the thymus from bone marrow progenitors.

Question 5

What do CD8+ T-cells become?

Answer 5

They become effector cytotoxic T lymphocytes (CTLs)

Question 6

What is the difference between the different subsets of CD4+ helper T-cells?

Answer 6

Each subset produces a distinct cytokine profile and regulates distinct activities within the body.

Question 7

True or False?:

T_H1, T_H2, T_H17, T_REG, and T_FH are all subsets of CD8+ T-cells.

Answer 7

False

T_H1, T_H2, T_H17, T_REG, and T_FH are all subsets of CD4+ helper T-cells.

Question 8

What causes activation of CD4+ T-cells?

Answer 8

CD4+ T-cells are activated upon binding Ag presented by MHCII.

Question 9

What causes activation of CD8+ T-cells?

Answer 9

CD8+ T-cells are activated upon binding antigen presented by MHCI.

Question 10

What does the TCR recognize?

Answer 10

The TCR recognizes pMHC complexes on the surfaces of APC.

Question 11

CD3, ζ chains, and ITAM motifs are all part of what immunological structure?

Answer 11

TCR Complex

(Note: The recognition subunit is also a part of the complex.)

Question 12

True or False?:

T-cells form an “immunological synapse” with B-cells.

Answer 12

False

T-cells form an “immunological synapse” with APCs.

Question 13

What does the structure of the TCR recognition subunit consist of?

Answer 13

The TCR recognition subunit is a hetereodimer of chains with Ig-like domain structure. They each have a variable region, constant region, stalk segment, transmembrane region, and cytoplasmic tail. They are bound together via a disulfide bond between their stalk segments.

Question 14

True or False?:

Most TCR recognition subunits are γδ TCRs but some (<10%) are αβ TCRs.

Answer 14

False

Most TCR recognition subunits are αβ TCRs but some (<10%) are γδ TCRs.

Question 15

What does it mean to say that TCR recognition subunits are clonotypic?

Answer 15

This means that each T-cell clone expresses only one type of TCR of the same specificity.

Question 16

True or False?:

TCRs are secreted.

Answer 16

False

TCRs are transmembrane proteins and are not secreted.

Question 17

What acts as the ligand for a given TCR?

Answer 17

The ligand of a given TCR is a pMHC complex on the surface of an APC.

Question 18

Why are there two different classes of MHC?

Answer 18

There are two MHC classes to cover the two main types of pathogens: intracellular and extracellular.

Question 19

What do MHCI molecules bind and present?

Answer 19

MHCI molecules bind and present peptides generated within the cell (endogenous peptides).

Question 20

What do MHCII molecules bind and present?

Answer 20

MHCII molecules bind and present peptides of extracellular origin (exogenous peptides).

Question 21

How do MHCI and MHCII differ in structure?

Answer 21

MHCIs α chain has three domains, is transmembrane, and noncovalently binds a non-transmembrane and invarient β₂ microglobulin while MHCIIs α and β chains are both transmembrane and both have two domains.

Question 22

What animal does MHCI look like?

Answer 22

Moose :)