Lecture 3

T cells have   that can only sucessfully bind to an antigen if it is held in a very stable manner.

  = any substance that can induce a specific immune response

Everyone has MHC receotors so technically they are  . Some cells are professional antigen presenting cells, like  ,  , and  

T cells are in  

The dendritic cells bring antigens to lymph node and displau them to  

  leave the lymph node and access the blood cirulation to traffick to tissues

MHC class I
( ,  , )

MHC Class One are expressed by all  
Presents peptides derived from  sources

MHC Class Two are expressed by   and select others. Presents peptides derived from   sources.

MHC Class II
( ,  ,  )

Only professional antigen presenting cells will bind antigens from   of the body and fuse with a phagosome.

CD8 + T cells
• T   (Tc) cells
• TCR can only recognize peptides when bound to
 
• Cytotoxic functions to eliminate   or
  cells and   cells

CD4+ T cells
• T   cells
• TCR can only recognize peptides when bound to
 
• Produce cytokines to direct activities of other
  and   cells

Dendritic cells can capture viruses take them in and put them extenally on   molecules. This is called cross-presentation and only   cells can do this.

T cells are   until activated by antigens. When they get activated, they multiply by c . They end up getting stimulated to differeniate. The become   T cells and   T cells.

3 signal method of T cell activation
Step 1: Peptide recognized by  

3 signal method of T Cell activation
Step 2: Costimulation
DC expresses ligans CD  and CD  that bind to receptor CD  on T cells that provide enhancement of   signals

3 signal method of T Cell activation
Step 3
 produces cytokines that bind to receptors on   to direct gene expression. Produces specific subtypes of  to respond to specific microbes

Naïve T cells are activated to differentiate
into   T cells. Polarizing   are provided by   that turns on   induced by cytokines. This produces specific T cell subtypes.

IL-6 and TGF-B produce  cell that makes   which produces 

IL-4 produces   which makes  ,  , and   that is responsible for   and  response

 , ,   makes   cell that produces   and   which is responsible for cell-mediated ,   actuvation, and  

T cells from the blood circulation enter the lymph nodes
through  and
localize in the 

Effector Tc cells or cytotoxic T lymphocytes
(CTL) release cytotoxins to induce  

Cytotoxic T lymphocytes finds target cells by binding  peptide with the  
This is sufficient to induce release of the
cytotoxins (  and  )

  forms pores that allows the   to slide through

Granzymes activate  which degrade DNA

B cells in the lymph nodes do
not need   presented but
can directly bind to it as the
 flows into the organ

THf cells are activated to produce
  and express  
required for the production of
 

Activated B cells
differentiate into  
cells which produce
 

*****  are proteins that can
bind directly to antigens to
prevent microbe spread and
promote elimination
Also called
 

B cells engage antigen
and become activated if
the  
recognizes the antigen. The antigen is also taken
up and processed –
peptides are displayed on
 

Dendritic cells present antigen to   and induce activation
if the TCR recognizes the
antigen

The activated Tf cells
interact with the activated
  in the area
between the T and B cell
zones

Some of the activated B
cells receive signals from
the   to differentiate
into   to
produce the first amount
of antibody ( ) (IG type?)

Others of the activated B
cells return to the   to undergo
expansion and
differentiation into  

Long-lived plasma cells
leave the lymph node and
traffick to the affected
tissues to produce 

Other activated B cells
differentiate into  and some longlived plasma cells that
reside in the  

 (type of antibody) is most commonly found in oral mucosa, esophagus, and gut

  is the highest level of opsonization and neutralization activties.

 is produced first upon antigen invasion. Increases transiently.

  is expressed in muscoal tissues and forms dimers after secretion

 has an unknown function

  is involved with allergy

The  portion of the antibody has the effector function

Ig are composed of two   and two 

Each H chain gene encodes for a specific  

Isotypes provide antibodies with different effector functions based on  interations with different proteins and cells

The   genes make the different antibodies

  is always the antibody involved in first response

DARK ZONE
Activated B cells entering the B cell zone
( center) undergo robust
proliferation
Mutate the antigen-binding site to improve
binding =  
Once completed – the B cells then interact
with the   in the light zone

LIGHT ZONE
B cells expressing   with strong binding
to the particular antigen outcompetes other
B cells and remains attached follicular DC =
 
All of the low affinity BCR B cells undergo
 (disadvantageous mutations)
Survival B cells differentiate into plasma
cells; later others change out H chains =
class switching

THf cell cytokines help direct generation of
the different   isotype

IFN-y makes   (type of antibody)

TGF-B makes   (type of antibody)

IL-4 makes   and   (type of antibodies)

IL-2, IL-4, and IL5 make  (type of antibody)

 ,  , and  are involved in proliferation of cytokines

 ,  , ,  , and   do the differentiation of cytokines

Late time after administration Naive B vs. Memory B (time in days)

Time of peak response Naive B versus Memory B

Antibody isotype produced

IgG is able to trigger the release of   and   to induce apoptosis

 is able to bind to an infected cell, which allows for   cell to find and results in the killing of the antobody coated cell. The Fc receptor only recognizes IgG! Process is called  

Phagocytes (neutrophils and macrophages) express   receptors that bind to the   of  
Triggers phagocytosis ( 

Cleaved   components can also bind to microbes/antigens (triggers phagocytosis)
o Phagocytes express complement receptors for these components
o EX –   bound by  

Complement components serve as  (enhance
phagocytic uptake)

IgM can bind to the surface of microbes
Recruits a  

C1 binding triggers a enzymatic cascade
resulting in creation of the  
MAC forms pores in the membranes of
microbes resulting in  

MAC permits  resulting in
cell lysis

IgG and IgA can bind to  expressed by
microbes required for contact with the host
cells
The antibodies   with host cell receptor preventing
either colonization or invasion

The goal of vaccine development –
generate a population of  cells to
secrete neutralizing   to block or minimize
infection of cells by a specific microbe

Anti-toxins also use neutralizing  to block
toxin binding to target receptors

IgE is produced during a  response ( influence)

IgE binds to antigens on  

Eosinophils express   ( ) that bind to the   region of  
Triggers release of granule contents that destroy the microbes

IgE can be produced in response to certain
 

IgE is captured by   receptors on
mast cells in the tissues (initial exposure site)

First exposure = no symptoms but generation
of  
 held   binds to allergens upon reexposure

On rexposure from allergen, triggers pre-made   release by  producing a rapid inflammatory response. Mast cells release
  and   to promote
inflammation