Cells of the Immune System Flashcards
all cells of the immune system originate from stem cells in the bone marrow and complete their development there except…
t cells
what do the lymphocytes do
recognize and respond to foreign antigens
-specificity of immune system responses is due to lymphocutes
what are immunoglobulins
antigen receptors on B cells
what are antigenic determinants or epitopes
frangments of antigens
what phases of the specific immune response depend on antigen presenting cells (APCs)
recognition and activation phases of specific immune responses
what are the 3 major classes of lymphocutes
T cells
B cells
natural killer cells
how are lymphocytes shaped
small cells (8-10 microns) absence of specific granules round centrally placed heterochromatic nucleus thin rim of basophilic cytoplasm
which are the only cells capable of producing antibodies
B cells
what is capping
antigen receptors move w/in the fluid plane of the B cell membrane and aggregate at one pole of the cell
where are plasma cells found
where do they nomrally not circulate in
lymphoid organs
sites of immune responses
-normally do not circulate in the blood or lymph
what 2 types of antigens do B cells respond to
T cell independnet
T cell dependent
T cell independent antigens can directly bind to B cell antigen receptors and induce….
induce B cell activation and antibody production
what are some examples of T cell independent cell antigens
polymeric antigen esp polysacc as well as glycolipids and nucleic acids
what is endotoxin
an important T independent antigen present in bacterial cell walls
what do T cell dependent antigetns require in order for B cell activation and antibody production to occur
T cell B cell cooperation
what are some examples of T cell dependent antigens
proteins and polypeptides
what type of T cell is required for T cell dependent activation
helper T cell
what do B cells differentiate into
plasma cells
how much % do T lymphocytes make up of the lymphocyte pool
70%
how much do B lymphocytes make up of the circulating lymph?
30%
what is the major hisocamptibliilty molecule (MHC)
a region of highly polymorphic genes whose products are expressed on the surface of a variety of cells
what are the 2 types of MHC molecutes
where are they located
class 1 MHC molecules on all body cells class 2 molec located exclusvely on cells of the immune system
MHC are encoded for in a regino of ______ and referred to as ______
chromosome 6
referred to as the human leukocyte antigen (HLA) region
what type of MHC restriction do helper T cells show
class 2 MHC restriction
what are T lymphocytes devided into
helper T cells (CD4+)
cytotoxic T cells (CD8+)
APCs and accessory cells are specialized macrophages which engulf peptide antigens and process them so that they become….
incorporated into the class 2 MHC molec on their cell surface
where do class 2 molecules acquire peptides from
intracellular vesicles following uptake of microbes
what is an epitope aka antigenic determinant
during the processing of MHC only a small fragment of the original antigen becomes associated w/ class 2 surface molecules. the particular fragment=epitope
in response to antigenic stimulation, what do helper T cells secrete
protein hormones called cytokines
what is the function of cytokines
promote the proliferation and differenetiation of T cells, B cells, macrophages, which ultimatetly facilitate removal of antigen
what do cytokines recruit and activate to provide a link btwn specific T cell immunity and the infl response
inflammatory leukocytes
how are CD8+T cells presented antigen
what is it similar to
by dendritic cells that express viral and tumor antigens in their cytosol in a manner similar to how dendritic cells initiate CD4+ T cell responses
lymphocytes can only recognize a peptide antigen if that antigen is complexed w/ ….
either a class 1 or class 2 major histocompatibility complex (MHC) molectule
what MHC restrction do CD4+ helper T cells ahve
CD8+?
cd4=class 2 restricted cd8=class 1 restricted
do t cells bind to the antigen directly?
no, needs to be presented an antigen in context of an MHC molecule or else restricted
most ingested proteins do not enter the cytosolic class 1 pathway of antigen presentation, what is this unique to
dendritic cells
what surface protein do most helper T cells express
what surface protein do most cytotoxic T cells express
CD4=helper
CD8 =cytotoxic
what role does CD3 have
what is it noncovalently associated w/
role in signal transduction following antigen bindnig
-alphabeta heterodimeric T cell antigen
where are membrane proteins found
surface of B cells
macrophages
other leukocytes
how are natural killer cells different from T and B cells (lymphocytes)
lack cell surface markers that are present on T or B cells
do not develop in the thymus
what are natural killer cells role
- destroy tumor and microbe-infected cells before the antigens have the opportunity to stimulate a T or B cell response
- surveillance role in protected against tumor growth and microbial infections
what are nk cells distinguished by
numerous cytoplasmic granules that contain lytic compounds
how do nk cells destroy tumor, stressed, and microbially infected cells?
directly (similar to cytotxic T cells) and by antibody-dependent cell mediated cytotoxicity (ADCC) w/o MHC restriction
NK cells appear to specifically recognize tumor cells by …
virtue of the ADCC reduced expression of class 1 MHC molec
what do invariant natural killer cells (iNKT) recognize
-what are they presented by
lipid antigens, including bacterial antigens -presented by CD1 molec which are related to class 1 MHC molec
what are the functions of iNKT cells
thought to bridge effector functions of the innate and adaptive immune systems and may play an important role in anti-viral, anti-bacterial, infl, and autoimmune rxns.
what are lymphoblasts
following stimulation by antigen, small lymphocytes enlarge due to increased production of proteins and organelles to become lymphoblasts
-“blast transformation”
what are responsible for the accelerated response to antigen that is experienced upon re-exposure to antigen
memory cells
some lymphocytes differenciate from a cognitive stage to an effector stage (to eliminate antigen), what do others do
become memory cells
what are the top 3 most of the WBCs
- neutrophils
- lymphocytes
- monocytes
what is the instructional theory (which has been disproven)
antigen can induce a change in the lymphocyte to which it bound, inducing it to produce antibodies specific to itself
what is the clonal selection theory
individuals contain numerous clonally derived lymphocytes, each w/ a unique antigen specificity
- antigen binds only to that particular clone for which it is specific and activates it (clonally expands)
- lymphocytes circulate throughout the body to maximize the chance of interacting w/ their complementary antigen
what is the first cell type that enters the peripheral blood
monocyte
what cells are 12 to 20 microns in diamter, bean shaped nuclei and a cytoplasm lacking specific granules
monocytes
what are cells that lack specific granules
agranulocytes
what are macrophages
after spending a few days in circulation, monocytes leave the vasculature and take up residence in the tissues, where they mature and become macrophages
the maturation of monocytes to macrophgaes invloves…
an increase in cell membrane folds and an increase in the number of primary and secondary lysosomes
macrophages can be activated by a variety of stimuli and may assume differetn forms like…
- epitheliod cells (have abundant cytoplasm and resemble ep cells of the skin, they serve to wall off a site of infection to prevent its spread)
- multinucleated giant cells (macrophages fuse to form this and form around foreign bodies that are too large to be engulfed)
what are macrophages called when they are found in the lining of the vascular sinusoids of the liver
kupffer cells
what are macrophages called when they are found in pulmonary airways
alveolar macrophages
what are mononuclear phag role in innate immune function
phagocytosis
production of cytokines which promote inflmmation
what are monoculaer phag role in adaptive immunity
respond to T cell cytokines to become more efficient phagoccytes
- they can opsonize antibody-coated particles
- specialized subset can act as APCs
what are the granulocytes
neutrophils (polymorphonuclear leuk)
eosinophils
basophils
what are the agranulocytes
monocytes
lymphocytes
what do granulobytes participate in
immune response
also circulate in the blood
what are the bacteriocidal compounds in neutrophils
lactoferrin
lysozyme
defensins
why are neutrophils referred to as polymorphonuclear leukocytes
bc of their multilobed nucleus
whta are the characterisitcs of neutrophils
- respond to chemotactic stimuli
- phagocytic
- major cell population in the acute inflammatory response
what do eosinophilic granules contain compounds for
- compounds which are effective at combating parasites (ex. major basic protein)
- histaminase which is an enzyme which breaks down histamine
eosinophils are recruited to areas where histamine is relased from basophils and mast cells by….
eosinophil chemotatic factor
where are basophils found? whwere are mast cells found
basophils circulate in the blood
mast cells are found in the tissue
what do basophils secrete
histamine in respnse to various allergens by a mechanism known as immediate hypersensitiity
what do all phagocytic cells start as
monocytes
