Immune System

Question 1

Functions of CD8+ effector and CD4+ helper T cells?

Answer 1

CD8+ effector T cells

• recognize antigenic peptides from MHC Class I molecules.
• directly recognize and kill antigen-expressing cells

CD4+ T helper cells
-ability to orchestrate diverse immune responses which integrates adaptive and innate effector mechanisms.
-recognize antigenic peptides presented by MHC class II
molecules.
-produces a vast range of cytokines that mediate
inflammatory and effector immune responses.
-They also facilitate the activation of CD8+ T cells and B cells for antibody production.

Question 2

Define Antigen Presenting Cell

Answer 2

Any cell that displays on its surface an MHC molecule
with a bound peptide antigen that a T cell recognizes through its TCR.
-This can be a dendritic cell or a macrophage, or any
cell that expresses antigen and would be killed by an activated CD8+ effector T cell-specific response (such as a tumour cell or virally infected cell).

Question 3

Define Myeloid Cell

Answer 3

Any white blood cell (leukocyte) that is not a lymphocyte: macrophages, dendritic cells and granulocytic cells

Question 4

Define Regulatory T-cells

Answer 4

A type of CD4+ T cell that inhibits, rather than promotes,
immune responses.
-characterized by the expression of the forkhead transcription factor FOXP3,
-the lack of expression of effector cytokines such as IFN-gamma
-production of inhibitory cytokines e.g. TGF-Beta, IL-10 and IL-35.
-establish inhibitory cell-cell contacts with effector T-cells
-They are subdivided into ‘natural’ TReg (nTReg) cells, which develop in the thymus, and ‘induced’ TReg (iTReg) cells, which accumulate in many tumours and are thought to represent a major immune resistance mechanism.
-do express high levels of multiple immune-checkpoint receptors: CTLA4, PD1, TIM3, A2aR, LAG3,

Question 5

Define NK cell

Answer 5

Immune cells that kill cells using mechanisms similar to
CD8+ effector T cells but do not use a clonal TCR for
recognition.
-activated by receptors for stress proteins
-inhibited through distinct receptors, many of which
recognize MHC molecules independently of the bound
peptide.

Question 6

Define Macrophages

Answer 6

Specialized immune cells that, on stimulation by
pathogen-derived molecules or T cells, will engulf pathogens (particularly those that have antibodies or complement bound to them).
-They can also present antigen to T cells, but not as efficiently as dendritic cells.

Question 7

How do myeloid-derived suppressor cells influence immune cells and TME?

Answer 7

MDSC

• express arginase and release T-cell inhibitors such as nitric oxide
• suppress T-cell and natural killer (NK) cell activities
• ->cancer progression and metastasis.