B and T cells Flashcards
expressed on all nucleated cells
MHC I
presents endogenous/intracellular antigens
MHC I
presents viral or cytosolic proteins from within the cells
MHC I
antigen loaded in RER via TAP
MHC I
recognized by CD8 cells via TCRs
MHC I
Encoded by HLA-A, HLA-B, HLA-C
MHC I
composed of 1 heavy chain and 1 short chain
MHC I
beta-2 microglobulin
MHC I
expressed by all APCs
MHC II
present exogenous/externally-derived antigens
MHC II
presents bacterial toxins/proteins ingested by phagocytes
MHC II
antigen loaded in acidic-phagoendosome
MHC II
recognized by CD4 T cells via TCRs
MHC II
composed of 2 chains of similar lengths
MHC II (alpha and beta)
encoded by HLA-DP, HLA-DQ, HLA-DR
MHC II
associated with invariant chain
MHC II
invariant chain
placeholder occupies antigen-binding site, preventing binding by internal antigens until arrival at endosomes
invariant chain degraded in acidified endosome
MHC II
B cells mediate _____ immunity
humoral
B cells express
CD19, CD20, CD21
B cells originate from
bone marrow
B cells migrate to and reside in
lymphoid tissue
follicles of lymph node, white pulp of spleen
after B cell activation, they differentiate into
plasma B cells, memory B cells
B cell activation begins with
antigen presentation on MHC II
Signal 1: B cell activation
the foreign antigen presented by the B cell on MHC II is recognized by TCR on CD4 T cell
Signal 2: B cell activation
CD40 receptor on B cell binds to CD40L on T cell
the activated B cell undergoes ______ and _______
class switching; affinity maturation
antibody isotype depends on
cytokines secreted by T cell
the activated B cell proliferates in the
lymph node
effector B cells produced after activation
plamsa cells; memory B cells
provide humoral immunity by producing antibodies against antigen
plasma cells
found in bone marrow after B cell activation
plasma cells
normally do not circulate peripheral blood
plasma cells
develops antigen memory
Memory B cells
long lifespan (decades)
memory B cells
lifespan of plasma B cells
only survive months
B cells that do not produce antibodies
memory b cells
may proliferate and differentiate into plasma b cells upon reexposure
where are memory b cells found?
spleen, lymph nodes, tonsils
what B cell enables a quick antibody response on reexposure?
memory B cells
must be activated against a specific antigen
T cells
80% of circulating lymphocytes
T cells
mediate cell-mediated immune response via direct cell-to-cell contact
T cells
undesired T cell activity results in
Type 4 Hypersensitivity reactions
Signal 1: T cell activation
antigen binds to TCR
this is sufficient to activate CD8 t cells
Signal 2: T cell activation
B7 protein on APC binds with CD28 on Helper T cell
T cell differentiation begins in the
bone marrow
in bone marrow, T cells are double negative
do not express CD4 or CD8 or TCR
T cells migrate to _____ for positive selection
thymic cortex
In thymic cortex, T cells are double positive
express both CD4 and CD8, TCR gene rearragement occurs
TCR gene rearrangement
Beta gene, then alpha gene
Enables recognition of variety of antigens
positive selection
T cells must bind self MHC to survive
failed TCRs are eliminated by
positive selection
T cells migrate to ______ for negative selection
thymic medulla
in the thymic medulla, T cells are single positive
CD4 or CD8
negative selection
T cells with overly high affinity for self MHC antigens undergo apoptosis or become Treg
Tissue restricted self-antigens express on thymic meduallary epithelial or DCs due to
AIRE
AIRE deficiency causes
autoimmune polyendocrine syndrome -1
self-MHC is expressed by
thymic cortical epithelial cells
After differentiation, T cell migrate to
lymphoid tissues
spleen, lymph node, tonsils
Cytotoxic T cells kill
virus infected, neoplastic, or donor graft cells
Cytotoxic t cells express
CD8
CD8 T cells recognize antigens presented on
MHC I via TCR
When activated by abnormal antigen, cytotoxic T cells release granules containing
perforin and granzyme
perforin
created pore-like holes in target membrane
granzyme
enters perforin pores and activates caspases or other proteases to induce apoptosis
helper T cells express
CD4
Helper T cells recognize antigens bound to
MHC II via TCR
CD4 T cells are stimulated by
IL-2
primary target in HIV infection
CD4 T cells
Th1 cells
coordinate immune response against intracellular antigens
Th1 cell differentiation is induced by
IL-2 and IL-12
Th1 cell differentiation is inhibited by
IL-4 and IL-10
Th1 secretes
IFN-y and IL-2
IL-2 simulates
CD8 T cells and NK cells
IFN-y activates macrophages to kill
microbes
involved in granuloma formation
Th1
Th2 cells coordinate humoral immunity against
parasites
Th2 cell differentiation is induced by
IL-4
Th2 cell differentiation is inhibited by
IFN-y and IL-12
Th2 cells secrete
IL-4. IL-5, IL-10, IL-13
signals with IL-4 to preferentially promoted B cell IgE production
IL-13
Th17 cells
coordinate cellular immune response against fungi
Th17 differentiation is induced by
TGF-b and IL-6
Th17 secretes
IL-17, IL-21, and IL-22
stimulates neutrophils, fights fungal infections
Tregs
suppress immune system
Tregs prevent ______ by maintaining tolerance to self-antigens
autoimmunity
Treg cells express
CD25 and FOXP3
Treg differentiation is induced by
TGF-b
Treg differentiation is inhibited by
IL-6
Treg cells secrete
anti-inflammatory cytokines
TGF-b and IL-10
