Class Notes (835,873)
Canada (509,459)
Biology (529)
BLG 307 (38)
Clare Chua (38)


3 Pages
Unlock Document

BLG 307
Clare Chua

IMMUNOLOGY T CELL SELECTION AND CENTRAL TOLERANCE Tolerance-state of the immune system characterized by unresponsiveness to a particular antigen - ability to distinguish self from non self (unique and important to IS) FREEMARTIN condition in twin cattle: BURNET hypothesis -dizygotic twins sharing a placenta will therefore share RBC’s (hematopoitic chimera [share stem cells] -developing/immature lymphocytes are subject to CLONAL DELETION in presence if self-antigens are recognized CLONAL DELETION MODEL -self tolerance learned by developing immune system –occurs during fetal and neonatal development -tolerance decreases rapidly -if exposed to antigen in embryotolerance in adultrejection -If receptor of immature lymphocyte engages a self-antigendeletion of that clone T-CELLS – more important than B-cells for tolerance Central Tolerance – generated during lymphocyte development, involves clonal deletion Peripheral Tolerance – generated AFTER lymphocytes have matured involves ANERGY (inactivation) T CELL DEVELOPMENT (occurs in thymus in 3 stages) 1) TCR gene rearrangements resulting in productive α/β dimers on cell surface α/β have many more V/J segments than γ/δ δ is located within α(between J and V)  this prevents α/β and γ/δ co-expression -γ/δ actually occurs first (5% committed to distinct T cell lineage for innate immunity (double negative) 1. V/J rearrangements in α/β and γ/δ  usually α/β wins 2. β gene rearrangement completes first (double negative) -required to progress to double positive! (can induce SCID mouse with TCRβ transgene) -β pre TCR α complex associated with CD3 signals successful completion of TCRβ gene rearrangement -Without good TCRB cant place BpreTCRa or progress to the next phase -similar to μ-λ5-vpreB complex in developing B cells (λ5 is surrogate like pre TCRα) 3. CD4 and CD8 coexpression (but not in γ/δ) 4. if αgene rearrangement is successful  α/β TCR expressed on surface if unsuccessful  cell dies 2) CELLULAR SELECTION: Negative Selection – for self-reactive “thymocytes” Positive Selection – recognize foreign antigens in presence of SELF MHC 3) Acquisit
More Less

Related notes for BLG 307

Log In


Join OneClass

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

Sign up

Join to view


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.