The Immune System

Some updates • Exam 1 Wednesday • No LBL this week or class Friday (Steinmetz

Symposium)! • BNG Seminar TODAY!

– Lippman 017, Common Hour (w/ lunch) – Julie Czupryna, Ph.D.

• Technical Director, Optical Imaging Core, Upenn

• Outline for today – Exam 1 – additional example problem – Acquired Immunity II

“Beyond the Knife: Noninvasive Imaging of Disease in Small Animals”

Example exam problem 1 (modified)

Recall the result at left from LBL paper 2

a. What was the main result or takeaway from this figure?

b. The cells were plated atop collagen (a protein). What are the other three types of biomacromolecules (hint: one of the other three that is not a true polymer is lipids; the other two types are polymers).

c. Say the researchers wanted to make the PS particles less adhesive – give an example of a general strategy they could try (hint: think of the properties of a surface that affect adhesivity to cells)

H&E staining of MDMs exposed to HDPE particles for 24 h: (a) normal light; (b) polarized light . Original magnification x 100 (Note: takeaway portions removed!)

Example exam problem 2

Recall the result at left from LBL paper 2 a. How would you describe the major

takeaway or conclusion from this figure? b. Platelet response can be judged as a

combination of 1) number of platelets adhered and 2) platelet morphology. Which species was most active for each category based on the data here?

c. What is the difference between a platelet plug and a blood clot?

(Above): Categories of morphological forms (Left): Relative frequency of each shape on pyrolytic carbon

• Antigen • Immunogen • Pathogen

– viruses, bacteria

• Epitope • Immunoglobulin (antibody)

Immunogens, antigens, and antibodies

introduced these last class

• 5 classes of immunoglobulins in humans (antibodies, Ab) – Most Ab found in human

blood are the IgG type • Constitute 75% of plasma Ab • Only Ab to cross placenta and

circulate through the fetal blood

Immunoglobulins (antibodies)

http://www.beltina.org/pics/immunoglobulins.jpg

We will focus on the IgGs

• All classes of IgGs have heavy and light chains

• All heavy-light chains have variable and constant regions

• Antibody-antigen binding is very strong and sterically specific

• Light chain bonded to heavy chain with disulfide bonds

Immunoglobulins

http://www.cartage.org.lb/

Let’s come back to Ab when we discuss humoral immunity in

more detail

Immunity – Introduction • Acquired immunity has 2 subtypes

– Cell-mediated immunity – arises from cytotoxic action of cells

– Humoral immunity – from chemical activation of antibodies

humoral

http://www.frontiers-in-genetics.org/en/pictures/antibody_2.jpg

cell-mediated

Cell-mediated immunity

Both cell-mediated/humoral immuity have the same initial stages

1

1. The macrophage as an antigen presenting cell (APC)

http://apbrwww5.apsu.edu/

Major histocompatibility complex (MHC)

Cell-mediated immunity

Both cell-mediated/humoral immuity have the same initial stages

2

2. Helper T-cell activation by APC

http://www.bio.davidson.edu/

Cell-mediated immunity

3

3. Cytotoxic T-cell activation by APC

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/ClassIpath.gif

cell-mediated immunity: specificity is toward the MHC in combination with the antigen (as

we will see unlike humoral immunity)

Cell-mediated immunity

4 How does the activated cytotoxic T-cell destroy the APC?

4. APC targeting by activated cytoxic T-cell

http://sph.bu.edu/otlt/MPH-Modules/EH/EH_Immunity_B/Cytotoxic%20T%20Cells2.png

Immunity – Introduction • Acquired immunity has 2 subtypes

– Cell-mediated immunity – arises from cytotoxic action of cells

– Humoral immunity – from chemical activation of antibodies

humoral

http://www.frontiers-in-genetics.org/en/pictures/antibody_2.jpg

cell-mediated

Humoral immunity

1

B-cell activation

http://upload.wikimedia.org/wikipedia/commons/d/df/T-dependent_B_cell_activation.png

Humoral immunity

2

Memory versus plasma cells

won’t discuss these further

let’s look closer at these

Plasma cell Ab production • Plasma cells are differentiated, mature B-

lymphocytes that produce large volumes of Ab! – Also called plasma B cells, plasmocytes or effector B cells

Antibody contributions to immunity

• Ab contribute to immunity through two primary mechanisms

activation of the complement system

activation of effector cells

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter24/animation__the_immune_response.html