Unit 6 Adaptive immunity to Bacteria, virus, parasite Flashcards
what are T dependent anitgens
antigens that must be recognized by Th cells in order for immune system to be activated
activation of mature B cells by T dependent antigen steps
- internalization of antigen by APC
- Processing of antigens by APCs
- Presenting of antigens to Th cells by APC
- activation Th to produce cytokines
- activation of antigen specific B cells with Th cytokines
what does humoral immune response to antigens depend on
cooperation of Th, APC such as B cells
name the 3 APC
langerhans’ cells (dendritic), macrophages and B cells
APC express what on their cell surface
class II MHC
internalization of antigens occur via
phagocytosis or endocytosis
eg of internalization by APC
antigen specific IgM/IgD receptor-mediated endocytosis for B cells
what is antigen processing
the Ag is degraded into small fragments of antigenic peptides
location of dendritic cells
lymphoid tissue, connective tissue and epithelia
location of macrophages
lymphoid tissue, connective tissue and body cavity
location of B cells
lymphoid tissue, peripheral blood
macrophages present Ag to
Th1 cells
b cells present Ag to
Th2 cells
where does antigen processing and presentation occur
secondary lymphoid organs (bloodborne pathogens) and lymph nodes (pathogen invading tissue)
activation of resting Th lymphocytes require (2)
- antigen recognition
2. cytokine stimulation
what is antigen recognition for Th cells
Th cells through cell surface antigen receptors (TCR) recognize antigen peptide on MHC class II of APC
fn of cytokine stimulation for Th cells
resting Th cells activated by cytokines produced by APC
eg of cytokine stimulation
IL-1
fn of lymphokines
promote activation and replication of themselves or B cells
what produces lymphokines
activation of specific T h cells
activation of B cells require (2)
- antigen recognition
2. cytokine stimulation
what is antigen recognition for B cells
B lymphocytes through IgM/iGD receptors recognize and internalize antigens that will be presented to Th2
cytokine stimulation of B cells
locally acting cytokines (IL-4 from Th2) act early in activating Ag-specific B cell (clonal selection)
differentiation of activated B cells
clone of activated Ag-specific B cells will proliferate (clonal selection and expansion) and develop into plasma or memory B cells
plasma cells aka
antibody secreting or antibody forming cells
what is clonal expansion
clone of B cells specific for the Ag will multiply to great numbers
clonal expansion produces
mostly plasma cells and small number of memory B cells
features of plasma cells
produced in greater number, surface Ig absent, short lifespan, actively secrete Ab
features of memory b cells
small numbers, surface IgG/IgA present, long life span years long term immunity
thymic independent antigens are
capable of activating without Th cells
two types of TI antigens
TI-1 and TI-2
TI-1 antigens can
activate multiple clones of immature and mature B cells leading to polyclonal activation (non specific antibody response)
eg of TI-1 antigen
bacterial lipopolysaccharide
what are B cell mitogens
TI-1 antigens that induce B cell to undergo mitosis
what are TI-2 anitgens
large polymeric molecules with highly repetitive structures (eg epitotes)
eg of TI-2 antigens
bacterial capsular polysaccharides
TI-2 antigens can
crosslink B cell antigen receptor (surface Ig) on mature B cells leading to activation
why is immune response not effective against TI-1 antigens
antibodies produced are non specific
superantigens are
protein antigens that stimulate Th cells without being processed into peptides by APC
how do superantigens work
intact antigen bind directly to TCR and MHC II molecules enabling them to stimulate large number of T cells (2-20% of all T cells)
results of superantigen
massive production of cytokines produced by Th causing systemic toxicity and immunosuppression
eg of superantigen
staphylococcoal toxic shock syndrome toxin-1 TSST-1
effects of TSST-1
excessive amounts of cytokines-> systemic inflammation, hypotension and shock
thymocytes that mature in thymus differentiate into
cytotoxic T lymphocytes
what are CTL/Tc
CD8 +ive capable of killing abnormal cells (tumor or infected with intracellular pathogens virus)
CTL/Tc / killer T cells responsible for
cell mediated immunity
development of cytotoxic T cell response
abnormal cell expresses antigenic peptide in class I MHC on cell surface
what are the immunological synapse (interface) btwn Tc to abnormal cell
CD8 to MHC I
TCR to antigen
describe killing of abnormal cells by CTL
Tc bearing Ag-specific TCR activated and proliferate because of cytokines like Il-2. Tc seek out abnormal cells and destroy them by releasing granules
what do granules of Tc contain
perforins like granzymes
what are perforins
pore forming proteins related structurally and fnally to complement C9
how does perforin work
Tc insert perforins into membrane of abnormal cell –> lysis and death
what and where are granzymes found
group of enzymes found in granules of Tc, NK and lymphokine activated cells (LAK)
how do granzymes work
enter through holes created by perforins, degrade foreign proteins, trigger apoptosis and DNA degradation
fn of cell mediate immune response (Tc mediated response)
destruction of cells infected with intracellular microbes, defense against fungi, protozoa and parasitic worms, graft/acute rejection, destruction of tumor cells
what is TIL therapy
tumor infiltrating lymphocyte therapy for cancer
lymphocyte activated killer is
Tc and NK cells taken from patient’s peripheral blood
