Adaptive immunity Flashcards
immune memory consists of
T and B lymphocytes
T cells and antibodies can
recognise infinite number of targets
when does the adaptive system kick in
2-4 days after
adaptive immune system is specfic
to the given organism
why is the adaptive immune system useful
it is rapidly protective on re-exposure from the same infectious agent
property of the adaptive immune system
forms basis for the protective effects of vaccination
antigen
any molecules or part of a molecule recognised by the variable antigen receptors of lymphocytes are known as antigens
what does a vaccine do
- Priming the body for a pathogen
- Ability of body to remember an infectious agent to which it has been exposed – basis for natural and artificial immunity
- initiates production of memory cells
- they will recognise agent an produce massive number of lymphocytes and immunoglobulins that overwhelm invaders
founding father of immunology
Edward Jenner
E Jenner
- Observed that naturally occurring pustualar eruptions on the teats of cows could be transferred to the hands or arms of milkers but they had natural immunity against smallpox
o Demonstrated that injecting fluid from cowpox pustules into skin of children led to acquisition of a high degree of immunity to smallpox
the lymphatic system provides
a critical interact bw activated dendritic cells and lymphocytes
Lymphocytes enter the…
lymphoid tissue to be activated by dendritic cells
-return to the bloodstream though the lymph if not activated
what controls migrations through lymphoid tissue and cellular interactions
guided and controlled by adhesive cell surface molecules whose expression is regulated by cytokines and chemokine
name 4 innate granulocytes
neutrophils eosinophil basophil monocyte dendritic cell
name 2 cells of the adaptive immune system
B lymphocyte (matures in bone marrow)
T lymphocyte (matures in thymus)
name some lymph tissue
- adenoid
- tonsil
- lymph node
- thymus
- heart
- thoracic duct
- spleen
- Peyers patch in small intestine
- appendix
- large intestine
- bone marrow
- lymphatics- e,g. in legs
how do T lymphocytes recognise antigens?
via T cell receptors generated during their differentiation- they interacts wit AMPCs via complementary ligand
each T lymphocyte expresses an antigen receptor of only
one specificity- whole population of lymphocytes is collectively capable of recognising any antigen
describe the structure of the T cell receptor
- transmembrane
- invariant constant (c) region- closest to the membrane and the same in all T cells
- V variable regions made up of an alpha and beta chain and different in all T cells
what are Clusters of Differentiation
- major classes of T cells often referred to as CD4 and CD7
CD4
a marker of helper T cells- MHCII
CD8
a marker of cytotoxic T cells- MHC I
MHC are
co-receptors that plan an important role in signal transduction on antigen bind by T cells
dendritic cells
play a crucial role in activating the adaptive immune system
dendritic cells begin life
as a phagocyte but activated by conserved components of micro-organism of by inflammatory cytokines released by macrophages
once activated dendritic cells become dedicated to
displaying components of ingested micro-organism for recognition by naive T cells and subsequent differentiation of naive T lymphocytes into effector T cells
T lymphocytes role
CD8T+/cytotoxic T cells
kill viruses, infected and cancerous cells
T lymphocyte role
CD4+
activate other cells of the immune system
B lymphocytes
secrete immunoglobulins
lymphoid lineage
cellular differentiation
mature lymphocytes which have no yet encountered antigen are known as
naive lymphocytes
how Naive cells differentiate
differentiation into effector cells is stimulated by encounter with antigen and preceded with a vigorous proliferation that selectively expands the numbers of those lymphocytes with receptors specific for the inducing antigen.
clonal expansion of antigen-specific lymphocytes
where do T helper cells and cytotoxic T cells fully mature
peripheral tissue- äter stimulation in lymphoid tissue by dendritic cells
Natural Killer cells
Lymphoid lienage contains third major cell type which lacks antigen-specific receptors and is capable of killing virus-infected cells immediately without prior activation or clonal expansion.
Regarded as part of INNATE immune system- don’t need prior activation.
activation of NK cells
occurs via binding of activated receptors to surface molecules produced by cell damage e.g. cancer or those encoding infectious viruses
what stimulate the lymphoid pathway
cytokines
describe the lymphoid pathway
- Move into either blood stream or thymus (thymocytes- a nursery for T cells)- then move into the blood cell as mature but naïve helper T cells, then migrate to secondary lymphoid tissues and wait to receive info from dendritic tissues)
- Dendritic cells go straight from bone marrow into the blood and then to the secondary lymphoid tissue where is interacts with T cell
where are dendritic cells numerous
epithelial and mucosal surfaces
langerhans
o first recognised in the skin in the 19th century. They are as a subset of dendritic cells that reside in the keratinised epidermis for several months
Second population of skin-resident dendritic cells is found in the dermal layer - known as
dermal dendritic cells
in mucosal epithelium of the gut
dendritic cells are concentrated are specialised sites of antigen collection which overlie lymphoid tissues
some cells of the mucosal epithelium of the gut
have specialised surface properties that enable them to extend their long dendritic processes between the cells of the epithelium and into the lime to sample antigens
–> these cells are directly exposed to ingested antigens and to commensal bacteria
processes of the dendritic cell (in the mucusal epithelium)
have a specialized role in preventing inflammatory responses to harmless gut residents
summary of activation of the adaptive immune system
1) dendritic cell displays a component of microorganism for recognition by T cell bearing a receptor for that component
2) stimulates it to proliferate and differentiate into effector cell
3) when effector cell recognised the same antigen displayed on the surface of B cell, the T cell activates the B cell
4) B cell proliferates and secretes antibodies that recognised the micro-organism
T cell targeting
Unlike B cells whose surface immunoglobulin molecules are adapted to serve as antigen receptors, T cells are unable to interact directly with intact antigen so must interact with other cells of the immune system.
who do T cells know which cells to interact with
T cells are focused on their target cell by MHC molecules
- which carry fragment of antigen (usually peptide fragments of proteins) fro internal compartments of the target cell surface and display them for recognition by T cells
all naive T cells are
activated by antigen fragments displayed on MHC molecules on the surface of Dendritic cells
- after activation they are triggered to kill or activate cells displaying the same complex of MHC and antigen
which cells have MHC molecules
dendritic cells
who discovered that MHCs were related tot he rejection of skin grafts
Peter Medawar (1944)
Peter Medawar
Became a clinical immunologist because of WWII - the large number of burns victims presented an opportunity to research skin graft rejection. Established that the timing and vigor of rejection is
related to the degree of differences between histocompatibility antigens of donor and recipient.
- Differences in the MAJOR HISTOCOMPATIBILITY
COMPLEX result in rejection within the first week
- Differences in the MINOR HISTOCOMPATIBILITY
COMPLEX result in a slower rejection process.
Medawar’s work led the way to the routine use of tranplantation. Matching of major histocompatibility antigens, at times with the use of immunosuppressants, means that kidney, lung and heart transplants are now commonplace.
