Class Notes (838,988)
Canada (511,154)
Biology (1,140)
BIOL 2005 (40)

Cytolytic T Lymphocytes

3 Pages
Unlock Document

BIOL 2005
Elizabeth Nisbet

IMMUNOLOGY CD8 CYTOLYTIC T LYMPHOCYTES (CTL) -CTLS lyse target cells that display processed foreign antigens bound to MHC molecules. -free virus and bacteria cant trigger CTLs -pathogens replicating within host cells are protected from humoral immune response by intracellular environment -but peptide products appear on MHC I and are recognized by CD8 + CTLs -CTLs can eliminate infected cells even in the presence of excess soluble antigen Functions virally infected cells (MAJOR) bacterial infected cells tumor cells graft rejection *Important that their activity is confined only to target cells* Note: some CD4 and some NK cells also have cytolytic activity PROTECTION AGAINST VIRAL INFECTION -intravenous transfer of CD8 T cells specific for flue can protect against viral pneumonia! -CTLs can recognize conserved NP abundantly synthesized on the cytoplasm (thus catches HA/NA antigenic shift) -Class I (B-2microglobluin) and CD8 knockoutsreduced CTL levels and don’t clear virus -Perforin knockoutsnormal CD8+ numbers but don’t lyse virally infected cells Perforin plays central role in lysis of target cells by CTL -CTLs important in bone marrow transplant recipients and resoloving high vermia with HIV (delay AIDS) -Antigenic viral proteins can be cytosolic or nuclear-localized -generate vaccines through CTLsbroader immunity MECHANISM FOR VIRAL EXCAPE FROM HOST CTL Mechanism Demonstrated for 1. Viral latency HIV, EBV, Herpes simplex virus 2. Replication in “privileged sites” Neurotrophic viruses 3. Infection of class I –ve cells Polio, rabies 4. Inhibition of class I expression Adenovirus, Cytomegalovirus -E3-gp19K TM protein of Adenovirusthat associates in ER with MHCI and prevents export -US11 of CMV dislocates newly made MHCI from the ER into the cytosol 5. Inhibition of TAP function Herpes simplex virus -prevents transport of peptides into the ER 6. Mutation in CTL epitopes HIV, Epstein Barr virus, LCM virus (murine) ESCAPE MUTANTS) -mutations affecting processing, recognition by TCR, antagonism PROTECTION AGAINST BACTERIAL INFECTION -Several types of bacteria can reside and replicate WITHIN host cells -production of hemolysin protein that creates pores in intracellular membranes Salmonella: inside membrane vesicles Listeria, Myobacteria: escape into the cytosol -While this might elicit MHCII/CD4 response in some cells, certain cell types LACK these proteins -Mice that lack MHC I/CD8 expression are more susceptible to infection with intracellular bacteria -B2m critical for surface expression of MHCI and positive selection of CD8+ T cells -CTLS from mice infects with intracellular bacteria can specifically recognize infected target cells ACTIVATION OF CTL – -After activation, clonal expansion and expression of cytokines and cytolytic proteins (perforin, granzymes) -initial stages are CD4 independent, but CD4 is required eventually (helps with clearance and memory) Mechanism is unclear but maybe… CD8 needs more co-
More Less

Related notes for BIOL 2005

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.