Adaptive immunity- effector stage Flashcards
B and T lymphocytes are produced by the
bone marrow
where do T cells mature
in the thymus
where do B cells mature
in the tissues following contact with antigen
B cells make up
5-15% of lymphcytes
T cells make up
70% of lymphocytes
where do B and T cells accumulate
o Mucosa-associated lymphoid tissue (MALT)
o Lymph nodes o Spleen
lymphadenopathy
occurs when b and T cells are activated by the antigen
T cell receptors carry out
antigen recognition
TCR structure
α and β chains o CD3 complex
o Accessory molecules (CD4 or CD8)
diversity of TCR
huge diversity- can recognise all pathogens
- Combinatorial diversity (>10^16)
TCR recongise
peptides presented by MHC I and MHC II
subtypes of T lymphocytes
o Helper T cells (CD4+) recognise peptide
presented by MHC class II molecules
o Cytotoxic T cells (CD8+) recognise peptide
presented by MHC class I molecules
activation of T lymphocytes: role of costimulation
1) Signal 1: APC present pathogen peptide on its MHC (I or II depending on T cell type (CD8/4))
2) Signal 2: CD28 on complexes with B7 on APC
3) Signal 3: APC releases cytokines which stimulates the T cell
during T cell activation what happens to CD4 + T cells
they become T helper cells e.g. Th1 and Th2
during T cell activation what happens to CD8+ T cells
they become cytotoxic T cells (CTL)
Activation of T helper cell response (CD4+ T cells)
APC will release cytokines which will stimulate the naive CD4+ T cell to become a specific type of T helper cell (H1, TH2, TH17, Treg)
TH1
- cell mediated immunity- for intracellular and extracellular pathogen*
- stimulate CD8 T cell differentiation
- recruitment and activation of macrophages
- stimulate production fo IgG or IgA from B cells
TH2 and TH17 mediate
humoral immunity- defence against extracellular pathogen (parasite, worms)
TH2
- stimulate B cells to produce IgE
- stimulate eosinophils to kill pathogens
- Allergic response from mast cells
TH17
recruitment and activation of neutrophils
Treg
tolerance and immune suppression
effector functions of CD8 T cells
1) APC binds to both Naive CD4 T cells and naive CD8 T cells
2) The CD4 T cell matures to become a TH1 cell
3) TH1 cell stimulates the Nazxive CD8 T cell to become and effector CD8 T cell
4) CD8 T cell becomes a cytotoxic T cell (CTL)
5) CTL moves to peripheral tissue and jills all infected cells (senses infected cells by their MHC class I)
6) Other naive CD8 T cells will become memory CD8 T cells
in general CD4 T cells
increase phagocytosis and increase production of antibodies by plasma cells
B cells receptors are
membrane bound antibodies
- unique specificity for each cell
