Lecture 2 - Cells and Tissues of the Immune System Flashcards
What is a leukocyte
white blood cell
what is a lymphocyte
type WBC (T cell, B cells, NK cell)
What type of nucleus do granulocytes have
polymorphonuclear; mutli-lobed nucleus
What type of nucleus do mononuclear cells have
single rounded nucleus
Examples of granulocytes
neutrophils, eosinophils, basophils
Examples of mononuclear cells
lymphocytes, monocytes
Which mononuclear cells are phagocytic
monocytes
Which mononuclear cells are not phagocytic
lymphocytes
What cells are important in blood clotting
platelets
What percentage of WBCs in circulation are basophils
0.5%
What granulocytes take up acid dyes
eosinophils
What granulocytes take up little dye
neutrophils
What granulocytes take up basic dyes
basophils
What is the half-life of basophils
1-2 days
What are granules in basophils filled with
inflammatory mediators
What type of infections are basophils important in
allergy and parasitic infections (secondary to eosinophils)
What granulocytes may be mast cell precursors
basophils
What percentage of WBCs in circulation are eosinophils
1-3%
What is the half-life of eosinophils
30 minutes
What are granules in basophils filled with
potent mediators (major basic protein and eosinophilic cationic protein) capable of killing parasites
How long do eosinophils live in tissues
couple of weeks
What are eosinophils important in controlling
extracellular parasites
What percentage of WBCs in circulation are monocytes?
3-7%
What is the half life of monocytes
1-2 days then migrate to tissue and differentiate into a macrophage
What WBCs are found in most tissues and are extremely important in immune response
macrophages
What do monocytes differentiate into
macrophages
How are macrophages important in the immune response?
- phagocytosis and killing of bacteria
- presentation of antigen by APCs on MHC II
- secretion of cytokines
Major role of cytokines
major role in inflammation and immune response
What is the order of how WBCs arrive at infection
neutrophils, monocytes/macrophages
What is a sign of chronic infection
accumulation of monocytes/macrophages at the site of infection
What % of WBC in circulation are neutrophils
55-90%
Half life of neutrophils in general
1-2 days
Half life of neutrophils in blood
8-10 hrs
How often are neutrophils replaced by new ones
2.5x per day
What spends a lot of energy making neutrophils
bone marrow
What are the first responders to infection and how fast do they arrive in substantial numbers
neutrophils, within 4 hours
Where do neutrophils exit the blood stream
at the site of infection
What do neutrophils do after arriving at the site of infection
accumulate in large numbers to ingest and kill the pathogen
What increases the production of neutrophils
bone marrow in response to bacterial infection
What is neutrophilia
increase in number of neutrophisl
What is commonly seen in animals with bacterial infections
neutrophilia
How is pus formed
neutrophils attack and destroy pathogens, especially bacteria and fungi, and die in the process
What is neutropenia
lower than normal numbers of neutrophils in the blood stream
What is commonly seen in animals with viral infections
neutropenia
What % of WBCs in circulation are lymphocytes
20-35%
What are types of lymphocytes
B cells, T cells, NK cells
HAlf life of lymphocytes
120 days
Where do lymphocytes circulate
between blood and lymphoid tissues searching for antigens
What is unique about lymphocytes
they circulate between blood and lymphoid tissues searching for antigens; other WBC stay in tissues once exiting blood
What lymphocytes can’t be distinguished morphologically
naive B and T cells
When do B and T cells die
when they do not come into contact with their antigen they recognize
What happens when B and T cells meet their antigen
they get activated and some differentiate into memory cells
What is a cognate antigen
the antigen B and T cells are looking for
What do guard cells under epithelial cells do
recognize pathogens and secrete cytokines that act on endothelial cells->start showing receptors->signal neutrophils
What are important for regulating leukocytic traffic
endothelial cells
Wha are addressins
adhesion molecules on endothelial cells that allow circulating leukocyte to know where they are in body
When are addressin upregulated
during infection to faciliate binding of neutrophils to the endothelial cells and their subsequent exit to the site of infection
What do monocytes differentiate into
macophages and dendritic cells
All immune cells originate from …
bone marrow
What are the three lineages of immune cells
- erythroid
- myeloid
- lymphoid
Erythroid lineage
RBCs, platelets
Myeloid lineage
monocytes, neutrophils, eosinophils, basophils, some dendritic cells, mast cells
What cells are important in initiation of immune response
myeloid dendritic cells
lymphoid lineage
B cells, T cells, NK cells, some dendritic cells
What myeloid cells are released in a mature state
granulocytes
What myeloid cells migrate to tissues and mature
dendritic cells
What myeloid dendritic cells are important to initiating immune response
sentinel cells and APC
What myeloid cells leave bone marrow and mature in tissues and live from weeks to months and are important in parasitic infection and allergies
mast cell precursors
What types of infection are mast cell precursors important for
parasitic
T lymphocytes are released immature from bone marrow as pre-T cells and go to the ______ to mature
thymus
In the thymus, a T cell receptor is generated by _____
DNA rearrangement
What happens if the newly generated receptor recognizes antigen in thymus?
its eliminated
What happens if the newly generated receptor recognizes MHC molecule bu tnot antigen?
T cell matures and goes to secondary lymphoid tissue
B lympocytes are released immature from bone marrow as pre-B cells, which mature in _____??
primary lymphoid tissue
Where do B lymphocytes in birds mature?
Bursa of Fabricius
Where do B lymphocytes mature in mammals?
bone marrow
Where do B lymphocytes mature in ruminants
Peyer’s patch at ileocecum
Where does B cell develop its receptor (BCR)
primary lymphoid tissue
What happens if the BCR recognizes an antigen during development
its eliminated
What happens if the BCR DOES NOT recognize an antigen during development
it matures and goes to secondary lymphoid tissues
Why are NK cells released in the mature state
bc they are part of innate immune system
Where are NK cells released from
bone marrow
How do NK cells differ from B and T cells
not antigen specific
Which lymphoid cells have no memory
NK cells
When does differentiation in secondary lymphoid organ occur
when mature, naive B or T cell meets its antigen
What do B cells differentiate into
- effector plasma cells that secrete antibody
- memory cells which are long lived clones of the cell
What do T cells differentiate into
effector cells or memory cells
What is the first step of differentitation
clonal expansion of lymphocytes (mitosis)
What are primary lymphoid organs
thymus, Bursa, Peyer’s patches, bone marrow
What are secondary lymphoid organs
tonsils, spleen, lymph nodes, Peyer’s patches, bone marrow
What type of Peyer’s patches do Group I have
small dots in jejunum and long strip in ileum
What type of Peyer’s patches do Group II have
small dots in both jejunum and ileum
What increases chances of lymphocyte meeting its antigen
secondary lymphoid tissue
What are lymph nodes
lymphocyte rich tissue connected to lymphatic system, where adaptve immune response to lymph-borne antigen is initiated
What is spleen
site for adaptive immune response to blood borne antigens
What is MALT
mucosal associated lymphoid tissue, where adaptive immune response to antigens invading from the mucosal surfaces is initiated
Which way do primed vs naive lymphocytes go?
primed- towards tissue fluid
naive- towards lymph nodes
