BIOL 435 Ch. 2 Part One (Cells and Organs of the Immune System) Flashcards
immune responses rely on
-the development of specialized blood cells (WBCs/leukocytes (ex. lymphocytes))
>only the first step
immune responses result from
- coordinated activities of many cells, organs and microenvironments in the body
- cells must interface with each other to trigger immune responses
- interfaces and tissues involved are complex
hematopoietic stem cells (HSCs)
-have the ability to differentiate into many types of blood cells
all RBC and WBC develop
-from multipotent HSC during hematopoiesis
totipotent
-can become any part of the embryo or placenta
multipotent
-differentiate into many cells but NOT into every type of cell
hematopoiesis
- a highly regulated process
- in adult vertebrates it occurs in bone marrow
- early on it occurs in various places as development proceeds
within bone marrow
-HSCs are constantly renewed and directed to differentiate into 2 major types of progenitor cells
2 major types of progenitor cells
- Common myeloid progenitor cells
2. Common lymphoid progenitor cells
4 cells that develop from common myeloid progenitors
- RBCs (erythrocytes): 99.85%
- Monocytes
- Granulocytes
- Megakaryocytes
subtypes of granulocytes
- neutrophils
- basophils/mast cells
- eosinphils
- differ in granule staining and in protein content and function
neutrophils
- 50-70% of leukocytes
- phagocytic cells that differentiate in bone marrow
- circulate in peripheral blood for 7-10hrs, then migrate into tissues (not all released at the same time)
- life span in tissue: only a few days
- may secrete cytokines that regulate T- and B-cell activity
- engulf bacteria and release proteins
molecules in granules of neutrophils
- proteases
- antimicrobial proteins
- protease inhibitors
- histamine
proteases
- tissue remodelling
ex. elastase, collagenase
antimicrobial proteins
- direct harm to pathogens
ex. defensives, lysozyme
protease inhibitors
- regulation of proteases
ex. alpha1-antitrypsin
histamine
- vasodilation
- inflammation
eosinphil
- 1-3% leukocytes
- phagocytic granulocytes stain pink with H+E
- coordinate our defences against multicellular parasitic organisms (worms)
- cluster around worms and release granules
- motile, migrate from blood into tissues
- most abundant in small intestines
- if no worms, may contribute to allergies + asthma
- may secrete cytokines that regulate T- and B- cell activity
molecules in granules of eosinophil
- cationic proteins
- ribonucleases
- cytokines
- chemokines
cationic proteins
- induces formation of ROS (ex. EPO)
- vasodilation, basophils degranulation (ex. MBP)
ribonucleases
- antiviral actiivty
ex. ECP, EDN
cytokines
- modulation of adaptive immune responses
ex. IL-4, IL-10, IL-13, TNF-alpha
chemokines
- attract leukocytes
- RANTES, MIP-1alpha
basophils
- less than 1% leukocytes
- nonphagocytic granulocytes containing large basophilic granules (stained blue in H+E)
- involved in response to parasites (parasitic worms)
- bind circulating Ag/Ab complexes then release granules
- histamine increases blood vessel permeability and smooth muscle activity (can be involved in allergies)
- allows immune cells to access the site of infection
- release cytokines that recruit other immune cells including eosinphils and lymphocytes
molecules in granules in basophils/mast cells
- cytokines
- lipid mediators
- histamine
lipid mediators
- regulation of inflammation
ex. leukotrienes
mast cells
- less than 1% of leukocytes
- non-phagocytic granulocytes involved in response to parasitic worms (contributes to allergies)
- released from bone marrow as undifferentiated cells
- mature only after they leave the blood into tissues
- large numbers of granules
- 1st immune response to allergies
pAPC
- professional antigen presenting cells
- monocytes/macrophages and dendritic cells (myeloid lineage)
- secrete proteins that attract and activate other immune cells
- internalized pathogens, digest them into proteins and present them on cell surface in MHC class II
- up-regulate costimulatory molecules required for optimal activation of helper T-cells
- important between innate and adaptive immunity
monocytes
-2-12% of leukocytes
-migrate into tissues and differentiate into macrophages
>function to repair, destroy pathogens + present antigens
-can also differentiate into dendritic cells
>HIGH degree of function as ‘ingestors’ of antigens followed by presentation to naive T lymphocytes for initial activation
macrophage
- along with neutrophils are specialized for phagocytosis
- can present antigens to T cells via MHC (=pAPC)
- first to fight pathogens
- some arise from embryonic cells as tissue-specific (resident)
tissue-specific(resident) macrophages
- used to think they all came from monocytes
- some arose earlier and are maintained
- specific jobs dependent on cell type
dendritic cells
- the most potent APC for activating naive T-cells
- immature ones capture antigen, then mature and migrate out of that location to another to present antigen to T-cells
- can be formed through myeloid progenitor cell or monocytes (both innate and adaptive immunity)
megakaryocyte
- large myeloid cells (reside in bone marrow)
- give rise to 1000s of platelets
- have properties of individual cells, but do not have their own nuclei
platelets
- small cells or cell fragments
- circulate in the blood and participate in the formation of blood clots
life spans
- RBC: 120 days (recycled)
- platelets: 5-10 days
H + E stains
- hematoxylin (binds to negatively charged stuff (ex. DNA) = purple
- eosin (cytoplasm and other stuff = pink)
neutrophil extracellular traps (NETs)
-‘eject’ DNA and create a net to capture bacteria (sacrifice)
simple pAPC
- present antigen to T-cells
1. Phagocytosis (big)
2. Receptor mediated endocytosis
3. Pinocytosis (small stuff) - bring in and cut into Ag (peptides)
IgE
-comes from B-cells
>allergen=antigen
-binds to mast cell IgE receptor
APC
-B-cells
>not professionals
MHC classes
- MHC 1: all cells
- altered self (ex. virus, cancer)
- activated by cytotoxic T-lymphocyte (CTL) - MHC 2: APC
- activate T-helper cells
APC and MHC
- Fragment of protein inside cell associates with MHC and is transported to the cell surface
- Combo of MHC and antigen is recognized by a T cell, altering it to the infection
3 common lymphoid progenitor cells
- B lymphocytes
- T lymphocytes: subset that appears more simlar to NK cells=NTK cells
- Innate lymphoid cells, including NK cells
* 20-40% of circulating WBCs
- 99% of cells in lymph
lymphocytes
-appear very simlar, but different sets carry different molecules on their surface
>cluster of differenitiation (CD) molecules
B-cells, T-cells and NK cells
- express many different CD proteins
- B-cells also express the BCR
- T-cells also express teh TCR
- memory cells from B and T-cells
T helper vs. T cytotoxic cells
-undergo gene rearrangement
>CD4: T helper cell
>CD8: T cytotoxic cell
-could have same TCR
BCR
-essentially antibodies on cell surface
-antigen can bind to 1 or 2 arms (‘different’ receptor)
>increase signal to inside
-2 heavy chains and 2 light chains
TCR
-2 chains
-bind to peptide held out by MHC
>MHC II: T-helper cell (CD4 must also see MHC II)
>MHC I: T-cytotoxic cell (CD8 must see MHC I)
