Class Notes (838,343)
Canada (510,861)
Biology (1,140)
BIOL 2005 (40)
Lecture

Immunology vs Cell Tolerance

3 Pages
67 Views
Unlock Document

Department
Biology
Course
BIOL 2005
Professor
Elizabeth Nisbet
Semester
Fall

Description
IMMUNOLOGY T CELL TOLERANCE -Generation of diversity is a stochastic post germ line encoded event. -The ability to discern btw harmful and innocuous antigens is learned in the neonatal period -Auto reactive lymphocytes recognize self antigens and are deleted. -Foreign antigens introduced during that period would also induce tolerance -“Horror autotoxicus” would result from a break down of tolerance to self (ex: Diabetes I attacks Islet cells) OLD VIEW: Self-nonself / antigen driven / developmentally determined NEW VIEW: context model/ circumstance driven/ determined by milieu Context Model for Self-Non Self Distinction -Immune system activated by PAMPS (ex: LPS on pathogens) triggering PRRs (ex: toll receptor) -Adjuvant induced activation necessary for productive IS. Without ittolerance Danger Theory -Ag presented in presence of dangerproductive immune response Ex of Danger Signals: Molecules released during injury and necrotic cell death (heat shock proteins) -Ag presented in absence of danger tolerance -Decision of Tolerance or Productive Response by State of APC When activated b/c of infection, inflammation, PAPMPS or danger, d APC upregulates: Signal One: Presentation of antigen to T cells. Alone anergy/deletion Note: APC doesn’t need costimulation once it is activated! Signal Two: Costimulatory molecules. Both signals  T cell activation Ex: CD28 on T cell binds B71 or B72 on APC Note: Origin of antigen is irrelevant, what matters is the environment it is recognized in (circumstance driven) Thus, Peripheral tolerance plays a critical role in preventing horror autoxicus. Mechanism of T Cell Tolerance (Thymus: Central Tolerance) -Thymus is where T cells develop and are educated. -Positive Selection = only T cells that can interact with self MHC molecules mature to CD4 + CD8+ -Negative Selection= T cell that binds to tight to peptide-MHC complex is eliminated (prevents self attack) NOT ENOUGH FOR EVERY SELF PEPTIDE IN THE BODY, SO TO INDUCE TOLERANCE. . . . Mechanisms of Peripheral Tolerance 1. Ignorance 2. Clonal Deletion 3. Anergy 4. T-regulatory cells 5.Immunoregulation IGNORANCE -auto reactive T cells found in the periphery but to do not respond and cause autoimmunity because (1)low levels of antigen (2)antigen sequestered -If access to abundant self Ag is attainedAutoimmunity (ex: Multiple Sclerosis) CLONAL DELETION -auto-antigen present at high levels and T cells are eliminated (after initial proliferation) T CELL ANERGY -T cell specific for a genetically engineered self antigen expand and then are rendered anergic. -T cells that only rec
More Less

Related notes for BIOL 2005

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit