L13 Fundamental Immunology Flashcards
(22 cards)
properties of innate immunity
first line of response, non-specific
rapid response, within minutes of infection
has no memory: same response after repeated exposure
does not lead to clonal expansion
mechanism of innate immunity
1st line: physical barriers or surface secretion like acidic pH in stomach or skin
2nd line: cellular defense mechanisms: natural killer cells, neutrophils, macrophages, mast cells, basophils and eosinophils
function of neutrophils
phagocytosis and activation of bacterial mechanisms
function of macrophages
phagocytosis and activation of bacterial mechanisms
antigen presentation
cytokine production to recruit other immune cells
function of natural killer cells
releases lytic granules > kill some virus-infected or tumor cells
properties of adaptive immunity
second line of response, specific
responds slowly, over days (relies of genetic events and cellular growth)
have memory: repeated exposure leads to faster and stronger response
leads to clonal expansion
two types of mechanisms for adaptive immunity
cell-mediated immune response: helper T cells and cytotoxic T cells
humoral immune response: B cells > antibody producing cells
where do cells of adaptive and innate responses come from
Hematopoietic stem cell in bone marrow differentiate into myeloid and lymphoid progenitor
myeloid: differentiate into innate immunity cells like dendritic and macrophages
lymphoid: differentiate into natural killer cells, T and B cell progenitors
what type of T cells recognise MHCII and MCHI
MHC II: CD4+ > activates > clonal expansion > differentiate into effector T cells
MHC I: CD8+ > activates > clonal expansion > differentiate into cytotoxic T cells
what do cytotoxic T cells do
kill infected cells by inducing apoptosis using pore forming molecules
steps for B cell activation
- antigen binds to B cell receptor
- antigen processed and presented on MHC II > helper T cell binds to it
what happens after B cell activation
clonal expansion and differentiation into plasma cells (secrete antibodies) and memory B cells
properties of antibodies
Y shaped polypeptides with 2 identical heavy chains and 2 light chains
five kinds of antibodies: IgG, IgM, IgA, IgD, IgE
antibody effector functions
virus and toxin neutralisation > prevents pathogen-host binding
opsonisation > phagocytosis
complement fixation and formation of membrane attack complex > phagocytosis or lysis
antibody-dependent cell mediated cytotoxicity > NK-induced apoptosis
MHC antigen presentation pathway
class I: endogenous > antigen broken down > ER > MHC in Golgi > sent to surface membrane
class II: endogenous and exogenous
what is cross presentation of MHC
only for CD8+
process where APC takes in extracellular antigens but instead of presenting them on MHC class II, it presents on MHC class I
types of memory T cells from CD8+
resident memory cell (Trm): remain in tissue of primary reaction
central memory cell (Tcm): circulate through secondary lymphoid tissue
effector memory cell (Tem): circulate through non-lymphoid tissues
where do suppressor T cells come from and what is their function
differentiated from CD4
function: moderate immune response by T cells and B cells
difference between primary and secondary immune responses
primary:
- production of specific clones of effector cells and memory clones
- develops in several days
- does not limit the infection
secondary:
- more pronounced and faster
- more effective at limiting the infection
how does vaccination work
vaccine particles taken up by dendritic cells > activate adaptive immune response > T cells activated
vaccine particles recognised by B cells > B cells activated > antibodies produced; memory T and B cells formed > host prepared to mount immune response and protect the individual upon next exposure to pathogen
types of vaccines
live attenuated: weakened version of living microbe that can’t cause disease
inactivated: microbes killed with chemicals, heat or radiation
subunit: include antigens (or epitopes) that best stimulate immune system
toxoid: formalin inactivated toxins used as vaccine
functions of hemagglutinin and neuraminidase in Influenza
hemagglutinin (surface protein) used to bind to sialic acid receptors on host cell > allow virus to enter
neuraminidase helps release new viruses by cleaning sialic acid residues so they don’t stick
