INTRO TO SPECIFIC IMMUNITY Flashcards
what are physical barriers of the innate immune system?
skin
mucous memb
what is the inflammatory response of the tissues?
histamines
what are anti-microbial proteins?
complement
what are the cells of the immune system?
Neutrophils
Macrophages
Eosinophils
NK cells
what does the immune response rely on?
on the immunocompetent B cells and T cells
when do B cells develop?
continuously develop within the bone marrow
where do T cells develop from?
from pre- t cells that migrate into the thymus from the bone marrow
when do T cells arise?
before puberty but maturation tends to continue throughout life
what do mature T and B cells develop?
develop distinctive membrane bound proteins these proteins include antigen receptors, CD4, CD8 proteins
what do CD4 and CD8 proteins give rise to?
CD4+ and CD8 T cells
what are the 2 types of immune response?
cell mediated immunity and antibody mediated immunity
what does cell mediated immunity involve?
involves CD8+ T cells proliferating into cytotoxic T cells
what is cell mediated immunity associated with?
with targeting intracellular pathogens (fungi parasites and viruses), some cancer cells and foreign tissues
what does antibody mediated immunity involve?
the transformation of B cells into plasma cells
what do plasma cells synthesis and secrete?
immunoglobulins, or antibodies, and these bind to and inactivate specific antigens
what is antibody mediated immunity associated with?
with targeting antigens in the body fluids and pathogens that replicate in the body fluids
what are cell mediated and antibody mediated responses are aided by?
by CD4+ T cell derived helper cells
what are antigens?
Non-self molecular configuration
may be part of a single foreign protein or a molecule that is part of a large and complex structure such as a bacterium
what do antigens do?
activate the adaptive response eg antibody production
what is immunogenicity?
an ability to induce a response mediated by the production of specific T cells or specific antibodies
what is reactivity?
the ability to react with antibodies or specific T cells
what is an antigen?
a foreign particle that has reactivity or reactivity and immunogenicity
what are complete antigens?
foreign particles that have immunogenicity and reactivity
what happens with smaller substances that have reactivity but lack immunogenicity?
these can only stimulate an immune response if they combine with a larger carrier molecule
what are epitopes?
part of an antigen molecule to which an antibody attaches itself
what do T cells respond to?
to protein antigens
what do B cells respond to?
to proteins, lipids, carbohydrates and nucleic acids
how are antigens recognised?
only a small component of an antigen initiates an immune response, the epitopes
what happens when antigens come into contact with the immune system?
they are carried via the blood to the spleen, or via the lymph to the lymph nodes, where they are trapped by the reticular fibres of the reticular cells
what happens when antigens come into contact with the mucous membrane?
antigens are trapped by mucosa-associated lymphatic tissue (MALT)
what is needed for T cell development?
mature TCR
why are molecules expressed on the surface of cells important?
important in immune response
what is the Major histocompatibility complex MHC?
mhc
what does the MHC do?
guide recognition of antigen by T cells
bind epitopes of antigens and present them to T cells
highly polymorphic in the population
what is histocompatibility?
Self-cells express self-antigens in the plasma memb, the major histocompatibility complexes (MHC) antigens.
what are MHCs expressed by?
by every cell of in the body except the RBC
how does the MHC function?
by helping T cells recognise foreign antigens
what are the 2 types of MHC?
class I and class II
where are MHC I built into?
the plasma membrane of all the bodies cells
where are MHC II built into?
found only on the membranes of antigen presenting cells such as thymic cells and active T cells
what has lead to histocompatibilty and tissue typing?
that MHCs occur and that they play a part in the rejection of donor tissue
what is antigen processing achieved by?
by T and B cells recognising the antigen
what do B cells recognise?
antigens in the body fluids
what do T cells recognise?
antigens presented to them in combination with MHC
where do MHC proteins arise from?
fragments of self proteins
what do the fragments associate with?
with a peptide binding groove of a newly synthesised MHC molecule
what does the peptide binding groove do?
stabilises the MHC molecule and enable it to be incorporated into the cell memb as a functional self antigen
what happens if the protein fragment arises from a non-self source?
the newly synthesised MHC protein will then express a non self surface antigen
what 2 ways does the processing of foreign antigens occur?
exogenous antigen processing
endogenous antigen processing
what is exogenous antigen processing?
relates to antigens found in the body fluids
what are exogenous antigens initially dealt with?
by antigen presenting cells (APCs)
what do APCs include?
macrophages, B cells and dendritic cells
what do APCs ingest?
the antigen the antigen is then digested into peptide fragments
these are then transferred to small vesicle like structures
what do APCs synthesis?
MHC-II molecules that are packaged into vesicles so that the MHC –II molecules line the inner memb of the vesicles
what happens to the 2 vesicle types?
they fuse allowing the antigen fragments to combine with the MHC-II molecules
what are the large vesicles lined with?
with the antigen fragment/MHC-II complexes
what happens to the large vesicles?
they undergo exocytosis, which results in the antigen fragment/MHC-II complex being presented as an external component of the cell memb
what happens to the APC after processing?
APC then migrates to the lymphatic tissue where the antigen can be presented to the T cells
what are endogenous antigens?
antigens produced within a cell, and fragments of these become associated with MHC-I molecules
where does the antigen MHC-I complex moves to?
to the cell memb where it is displayed as a surface antigen
when do T cells recognise antigens?
when they are inside/associated with other cells of the body
what don’t T cells recognise?
free antigens
what do T cells recognise?
epitopes of antigens presented to them by MHC molecules on the surface of other cells in the body
what is the T cell response directed towards?
the “infected” or foreign cell
what are the 2 stages involved in the T cell activation process?
initial binding of a T cell with a specific antigen
co-stimulation
what are co-stimulants?
some cytokines, i.e. interleukin –2, and pairs of plasma cell memb molecules, that occur one on the T cell and one on the memb of the antigen presenting cells memb
how do co-stimulants function?
by allowing the two cells to temporarily attach to one another
do co-stimulants active T cells in the same way?
no, in a different way
what does lack of co-stimulation result in
T cell anergy
absence of the normal immune response to a particular antigen
what happens if fully activated by antigen presenting cells and the co-stimulant?
T cell proliferate and differentiate
where does the process of T cell proliferation and differentiation occur?
in the secondary lymphatic organs and tissues such as the tonsils
what are the 3 types of T cell?
helper T cells, cytotoxic T cells and memory cells
what are helper T cells?
T cells that express the CD4 memb protein normally develop into helper T (TH) cells
what so helper T cells recognise?
antigen/MCH-II complexes, and if costimulated by complimentary molecules on the antigen presenting cell, start secreting a range of cytokines
what do T helper cells secrete?
cytokines ie IL-2
how does IL-2 function?
by triggering T cell proliferation, functioning as a costimulator for TH cells and cytotoxic T cells, and it can enhance the proliferation of B cells and natural killer cells
what do cytokines do?
Enhance immunocompetent cell function
what are cytokines?
small hormones that can stimulate or inhibit cellular differentiation, proliferation and growth
what is cytokine therapy?
because of their ability to regulate immune processes they are now being used to treat medical conditions
where are cytotoxic T cells derived from?
from CD8+ cells
what do TC cells recognise?
antigen/MHC–I complexes on virus infected cells, on the surface of some cancerous cells and on the surface of transplanted cells/tissues
when can TC cells become cytolytic?
if this antigen recognition is associated with costimulation with cytokines such as IL-2
when are cytokines secreted?
as a result of the T-helper cell secretion
when can activation of Tc cells occur?
occur if these T helper cells have also encountered the same antigen coupled to MHC-II
what happens when Tc cells become activated?
they rapidly proliferate and then destroy the target cells
how do Tc cells destroy target cells?
by secreting porforin
or lymphotoxin.
what else can T cells secrete?
gamma interferon, and this activates phagocytes at the site of infection
how are memory T cells formed?
from T cells that remain after an infection
what happens once memory T cells are formed?
these cells are maintained and allow a very rapid response to reinvasion by the initial antigenic materials
what do memory T cells ensure?
that re-infection by a previously encountered antigenic material is dealt with extremely quickly, before any signs or symptoms can develop
what happens to progenitor T cells from sites of haematopoiesis?
they begin to migrate to the thymus
what does T cell maturation involve?
rearrangements of the germ-line TCR genes and expression of various memb markers
what are thymocytes?
Developing T cells in the thymus
what do Thymocytes proliferate and differentiate into?
into distinct sub-populations of mature T cells
