intro to immuno Flashcards
what problems arise when the immune system fails to recognize self and non-self?
no self recognition = autoimmunity
no non-self recognition = no protection against infection
characteristics of innate immunity (in contrast to adaptive)
- present at birth (does not change with age)
- rapid
- relies on pattern recognition (common patterns of carbs/proteins on the surfaces of infectious organisms)
- not specific
- no memory
characteristics of adaptive immunity (in contrast to innate)
- slow on first exposure
- adapts to antigens
- very specific (recognition at the amino acid or DNA sequence level)
- memory
what cells/proteins are involved in humoral immunity?
B cells differentiate into plasma cells, which produce antibodies
what are the functions of humoral immunity?
targets extracellular immunity; antibodies…
- neutralize toxins/viruses
- opsonize bacteria
- activate complement
what cells are involved in cell mediated immunity?
T cells: helper CD4+ and cytotoxic CD8+
what are the functions of cell mediated immunity?
targets intracellular pathogens:
- directly kill virus infected cells
- inhibit fungi, parasites, and intracellular bugs
B cell functions
- differentiate into plasma cells => produce antibodies
- differentiate into memory B cells
- present peptides to T cells
T cell functions
- CD4+ helper T cells: secrete molecules to activate B cells and CD8+ cytotoxic T cells
- CD8+ cytotoxic T cells: directly kill cells
antigen vs immunogen
antigen = any substance capable of reacting with antibodies (proteins, small chemicals, polysaccharides)
immunogen = any substance that induces an immune response (proteins, but NOT chemicals or polysaccharides)
T cell dependent vs independent B cell response
Dependent = peptide antigens
- T cell recognizes a protein antigen => CD4+ T cell helps drive B cell response
Independent = non protein antigen
- B cell response to multivalent non-proteins
- IgM response
- No T cells required; APCs and B cells in spleen involved
- asplenic patients are more likely to have infection from encapsulated bugs
what is the function of MHC proteins?
present peptides on the cell surface to T cells
MHCI:
- on all nucleated cells
- recognized by CD8+ cytotoxic T cells
- alpha chain and beta2 microglobulin
MHCII:
- only on APCs (mΦ, dendritic cells, B cells)
- recognized by CD4+ helper T cells
- alpha and beta chains
how do T cell receptors and co-receptors interact to allow for antigen recognition?
TCR and co-receptor bind peptides presented by self MHC on the surface of other cells => can only recognize foreign peptides also in the context of a self MHC molecule
what are the two signals required for CD8+ T cell activation?
- Peptide recognition:
- any cell presents a peptide antigen on MHCI
- CTCR and CD8 co-receptor bind peptide - Cytokine signalling
- IL-2 secreted from CD4+ cells
=> CD8+ cells can kill via cytotoxin molecules
what two signals are required for CD4+ T cell activation?
- Peptide recognition
- APC phagocytoses extracellular pathogen and presents peptide on cell surface MHC II
- TCR and CD4 co-receptor bind peptide - Cytokine signalling
- APC B7 protein binds T cell CD28
- cytokine production and immune response
