Adaptive Immunity Flashcards
What are the 4 main characteristics of adaptive immunity?
- RECOGNITION - Immune cells’ ability to recognise own cells versus pathogen
- Lymphocytes tailored to combat specific antigens
- DIVERSITY - Many B and T cells that recognise a huge amount of antigens
- Immunological memory
What are the types of adaptive immune cells?
- B cells - humoral immunity - defense via antibody production
- T cells - cellular immunity - CD4+ helper cellls/ CD8+ cytotoxic cells/memory cells
Describe how the location of B and T cells change
- Both cells produced in bone marrow
- B cells mature in bone marrow/ T cells mature in thymus
- Circulate through blood and secondary lymphoid tissues(where they become active)
Compare and contrast the TCR and BCR.
- TCR - membrane bound αβ heterodimer
- BCR - membrane bound antibody
- Both have ITAMs - activate the cells
What occurs in positive and negative selection?
- POSITIVE - T cell in thymus binds moderately to MHC and survives
- NEGATIVE - T cell binds strongly - results in death of cell
Describe T helper and regulatory T cells.
- Both have CD4 surface molecules
- Both are activated by APCs presenting antigens associated with MHC II
- HELPER - orchestrate humoral/cellular immunity - activate macrophages/NK cells
- REGULATORY - Prevention of autoimmune responses
Describe cytotoxic T cells
- Have CD8 surface molecules
- Activated by APCs or infected nucleated cells presenting antigens linked to MHC II
- Destroys infected cells
Give three types of APCs
DENDRITIC
MACROPHAGES
B CELLS
How are cytotoxic cells activated?
- Dendritic cells process viral proteins
- Presentation of endogenous antigens with class I MHC on surface
- Activation occurs
What is required for T cell activation?
Antigen presentation with MHC II
What is antigen processing?
- Enzymatic process of degrading proteins through proteases into antigenic peptides.
- Requires energy (ATP) , movement of endocytic vesicles.
Describe MHC II antigen processing.
- Peptide production in phagolysosome
- Peptide binding by MHC
- MHC presents peptide at cell surface
Describe MHC Class I antigen processing.
- Antigen processing to peptide in proteasome
- Peptide transported to ER
- Peptide binding by MHC
- MHC presents peptides at cell surface
Describe Class II MHC mediated T cell activation.
- Maturation in thymus
- Forms CD4 cell with TCR
- Activation through binding to Class II MHC protein displaying antigen
- Mature to form effector cells - form memory/helper/regulatory T cells
Describe Class I MHC mediated T cell activation.
- Maturation in thymus
- Forms CD8 cell with TCR
- Activation by binding to Class I MHC protein displaying antigen
- Form memory and cytotoxic cells
Describe, in detail, activation of T helper cells.
- Dendritic cells engulf exogenous antigens, displays fragments on class II MHC protein
- CD4 T cell recognise antigen-MHC complex and bind
- Activated CD4 T cells proliferate and become memory and effector cells
What is the role of the T helper cells?
- Release cytokines
- Stimulate macrophages, neutrophils and NK cells
- Contribute to immunological memory
How do cytotoxic cells destroy infected cells?
- Perforin and granzyme secretion
