T Lymphocyte Function

activation of a naive CD4+ T cell requires signals through:

TCR alone
TCR and CD28
TCR and B7
TCR and CTLA-4

TCR and CD28

when an immature DC senses danger with PRRS, it will:

upregulate MHC class II
migrate to lymph nodes
upregulate B7
all of the above

all of the above

superantigens (SA) can cause a “cytokine storm” because:

SAs activate macrophages via PRR
T cells recognize SA peptides in MHC class II
SA bind invariant structures on TCR and MHC class II
SAs activate DCs via PRR

SA bind invariant structures on TCR and MHC class II

how many main CD4+ T helper cell subsets are there? what do they make?

FIVE main CD4+ T helper cell subsets that make signature
cytokines

which CD4+ T helper cell subset is predominantly made in response to viruses and intracellular bacteria?

Th1

which CD4+ T helper cell subset is predominantly made in response to parasites?

Th2

which CD4+ T helper cell subset is predominantly made in response to fungi and extracellular bacteria?

Th17

what is the common language of immune cells?

Cytokine-cytokine receptor interaction (Cytokines signal to cells that have the cytokine receptor)

what is a common approach to treating inflammatory conditions?

Blocking cytokines

• Monoclonal Ab specific for cytokine or receptor (Humira binds TNF to decrease inflammation)
• Kinase inhibitors

T CELL RECEPTORS ARE MADE RANDOMLY.

HOW DOES A T CELL ‘KNOW’ WHEN ITS DEALING WITH A VIRUS OR PARASITE?

dendritic cells can detect infection and what type of infection it is

what cells direct T cell differentiation via …?

Innate cells direct T cell differentiation via cytokines

Innate sensing of intracellular pathogens leads to development of which T cell subset?

Th1

Th1 cells activate effectors of

Cell Medicated Immunity (CMI)

Innate sensing of worms (and allergens) leads to development of which subset?

Th2

Th2 cells activate which cells?

eosinophils, basophils and mast cells

Innate sensing of fungi and extracellular bacteria leads to development of which subset?

Th17

Th17 cells activate ________ responses

proinflammatory – neutrophils, macrophages and epithelial cells

B cells are APCs, and therefore present peptides on MHC Class __

II

Nearly all B cell responses require which cell’s help

Tfh

how does Tfh activate naive B cells?

1. B cells present peptides from
   proteins internalized via BCR

2. Full B cell activation needs a second signal from a T cell

3. B receives second signal from CD40-CD40L interaction

The cytokine made by the Tfh cell influences what?

the class of the antibody made by the B cell

IL-4 will influence B cell to make which class of Ab?

IgE (parasite immunity and allergy)

IL-21 will influence production of…?

Promotes B cell memory and plasma cell formation

WHERE DOES B CELL ACTIVATION HAPPEN?

germinal centers

Tfh cells activate naïve B cells in primary/secondary lymphoid organs

secondary

walk through this figure

Some polysaccharides (such as lipopolysaccharide on Gram-negative bacteria) do NOT require T cell help for B cells to synthesize antibody. Without T cell help, what is the predominant antibody?

IgM (Little class switch recombination or somatic hypermutation)

• little memory responses (IgM is not made by memory B cells)

what are Thymus-independent (TI) antigens and responses?

Some polysaccharides (such as lipopolysaccharide on Gram-negative bacteria) do NOT require T cell help for B cells to synthesize antibody.

Activated CD8+ T cells become what? what do they ainduce?

CTL

apoptosis

how do Activated CD8+ T cells induce apoptosis?

Naïve CD8+ T cells must be _______- before they kill their target

activated

activation of CD8+ T cells requires what?

2 signals + IL-2

1. TCR-peptide-MHC interaction

2. B7-CD28 interaction with APC (usually dendritic cells).

   1. cross presentation: DC load exogenous peptide to MHC class I.

3. IL-2 from Th1 cells needed for clonal expansion

Cytokines from CD4+ Th1 cells are required for most viruses (eg HIV) to:

Activate naïve CD8+ T cells
Induce memory CD8+ T cells

Effector CD8+ T cells recognize what on nucleated cells

MHC class I + peptide

Activated CD8+ T cells kill target cells by two pathways:

1. Fas-FasL interaction induces apoptosis

2. Granzymes enter target via perforin channels and induce apoptosis

which molecules are important for B cell activation?

CD40 → co-stim molecule on APCs
CD40L → co-stim molecule on T cells

which molecules are important for CD4 and CD8 T cell activation?

CD28 → co-stim molecule on T cell (binds B7)
B7 → co-stim molecule on APCs (binds CD28)

CD4 binds MHC I or II

II

CD8 binds MHC I or II

I

what is the TCR signal transduction molecule expressed on all T cells?

CD3