Lecture 43 and 44 - b cells and t cells Flashcards
what class antibody is a pentamer
IgM
what class antibody is a dimer
IgA
which classes of antibody are monomers
IgG, IgD and IgE
primary response = following exposure to antigen
- slow rise in IgM
- slow rise in IgG
secondary response = following second exposure to antigen
- rapid increase in IgG
- limited rise in IgM
IgE
allergic response, trace amounts
IgG
4 types, main in blood, for killing bacteria
IgA
2 types, protects entry of pathogens, saliva, GI tract, respiratory tract (think A = At start)
IgM
in blood, 0mostly of opsonisation of bacteria
IgD
B cell membrane, helps in cell division
early Ig response
low affinity IgM
later Ig response
high affinity IgG
role of B cells
- antibody production
- T cell activation
- activation of innate immunity ( classical complement system)
Hep B
serious and common liver infection caused by virus
Hep B antigens
Hepatitis surface antigen (HBsAg)
Hepatitis core antigen (HBcAb)
HBsAg
immune to Hep B = active antigen
HBcAg
indicates past or current infection
Hep B vaccine
only has surface antigen = HBsAg, so if patient has been vacinated they will have anti-HBsAg
three types of T cells
- T helper cells
- T killer cells
- T regulatory cells
T helper cells
- activate phagocytes
- activate B cells
T killer cells
- cytotoxic T lymphocytes (CD8+ ve)
- effective at attacking viruses
T regulatory cells = Tregs
- not fully understood
- regulate and suppress other immune cells
- protect against autoimmune disease
APCs that T cells will respond to
- dendritic cells
- macrophages and monocytes
- B cells
T cells once activated release
IFNg (Interferon gamma) = cytokine that activates macrophages
T helper cells receptor
CD4+
cytotoxic T cells receptor
CD8+
B cell receptors to specific antigens
antibodies presented on surface on antigen
T cell receptors to specific antigens
Complex = to enable recognition of antigen
- MHC molecule: membrane bound protein protein complex CD3
- TCR
which receptor complex for T c cells
CD8+ interaction with MHC class I
-> all cells present MHC class I, if viral antigens are presented then needs to trigger Tc cell to kill infected cell
which receptor complex for T h cells
CD4+ interaction with MHC class II (professional APC)
-> APC cells present MHC class II together with foreign peptide (antigen) so need to trigger Thelper cells to release cytokines to trigger immune response
MHC class II
presented by professional APCs
MHC class I
presented by all cells, chopped up proteins from inside cell are presented on surface, normally are host protein fragments, but if viral components from viral invasion of cell = presented and recognised as foreign = triggers TC cells
“anergic” T cell
means T cell doesn’t respond to the antigen
T cell activation
- antigen processed in complex with MHC molecule (class I or II)
- second signal
second signal for T helper cell activation, CD4+ with MHC class II
on T cell = CD28 molecule
on APC cell = CD80 molecule
when T cell is activated = cytokine production
- chemoattraction
- autoactivation
- augmentation of inflammation
- stimulation of Ab production by B cells
monokines
cytokines released by macrophages
lymphokines
cytokines released by mature helper T cells
Th 1 cytokines
activate cell mediated immunity
Th 2 cytokines
responsible for antibody production
Th 1 cytokines list
IL-2
lL-15
IFNg
Th 2 cytokines list
IL-4
IL-10
IL-13
there are 2 T helper cell classes
Th 1 and Th 2
link between MS treatment and Graves’ disease, both autoimmune diseases
treatment of MS (Th1) can result in patient developing Graves’ disease (Th2) = monoclonal antibody targets CD52 on mature lymphocytes, kills them
HIV surface antigen
gp120 = binds to CD4 on T helper cell
treatment for myeolma using cytokines
IL-2 increase number of T lymphocytes, enhance immunosurveillance
central tolerance = B cells in bone marrow
- clonal deletion of cells that respond to self material
- receptor tolerance
immunological tolerance
failure to mount an immune response to an antigen, an be good but also bad
central tolerance = T cells in thymus gland
- positive selection, only cells recognising MHC molecules survive
- negative selection, clonal deletion, cells that recognise self material are killed
peripheral tolerance
- regulatory T cells can eliminate cells that recognise ‘self’
- absence of second signal to T cells (CD28 and CD80)
- anatomical barriers
- immune privileged areas
anatomical barriers
where immune system cannot reach
immune privileged area
protects vital structures, areas where introduction of antigens is tolerated without an inflammatory response that could destroy the tissue = eyes for example
what is an autoimmune disease = AD
when self tolerance against a body antigen is broken
organ-specific AD examples
- thyroid disease
- type 1 diabetes
- pernicious anaemia
- some skin conditions
non organ-specific AD
systemic lupus erythematosus (SLE) = lupus
cellular components of specific immunity
B cells and T cells
soluble components of specific immunity
immunoglobulins - b cells
cytokines - t cells
second signal for cytotoxic T cell, CD8+ with MHC class I
on Tc cell = 4-1BB
on APC = 4-1BBL