Cells and Organs of the Immune System Flashcards
What are the 3 lines of defense?
- Skin, MM, chemicals (innate)
- Phagocytosis, complement, interferon, inflammation, fever (innate)
- Lymphocytes, antibodies (adaptive)
Characteristics of granulocytes
WBC with cytoplasmic granules
produced in bone marrow
classified based on H&E stain
Types of granulocytes
Basophils (granules stain dark blue)
Eosinophils (granules stain red)
Neutrophils (granules stain neutral pink)
Characteristics of basophils
Defend against parasites
Allergic/inflammatory reactions
Toxic granules
Express adhesion molecules (LFA-1, Mac-1, CD44)
Characteristics of eosinophils
Defend against parasites - kill Ab coated parasites
Allergic reactions
Respond to chemokines secreted by neutrophils/lymphocytes
Toxic granules
Characteristics of neutrophils
Most numerous innate immune cell Band-shaped nucleus when immature Segmented nucleus when mature Circulate in blood Phagocytosis and degradation
What can a high ANC (absolute neutrophil count) indicate?
*Neutrophilia
Kidney failure or bacterial infection
What can a low ANC indicate?
*Neutropenia
Leukemia or bone marrow damage
Similar to basophilic leukocytes, _____ are generated in the bone marrow and have CD34+ precursor cells.
Mast cells
Two types of mast cells
CT mast cell - local allergic reactions
Mucosal - In areas of body exposed to external env (Lungs, digestive tract, mouth, nose)
Activated function of mast cells
Release granules containing histamine - mediate allergic reactions
Defend against parasites
Monocytes vs macrophages location
Monocytes - in blood
Macrophages - in tissue
Function of macrophages/monocytes
Phagocytosis and Ag presentation
Examples of tissue-specific macrophages
Bone - osteoclasts
Nervous - microglial cells
Liver - Kupffer cells
Histiocytes
Do macrophages always create an immune response while functional?
No, they also perform housekeeping functions such as recycling dead RBCs
Which cells recognize and kill virus-infected or tumor cells, and have features of both innate and adaptive immunity?
Natural Killer cells
What do the granules of the natural killer cells do?
Proteins form holes in the target cell and cause apoptosis
How do natural killer cells regulate the immune response?
Activate dendritic cells, T-cells, and macrophages
______ are specialized sentinel cells that move around and respond to their environment, presenting Ag to T cells.
Dendritic cells
Which immune cells promote self-tolerance?
Dendritic cells
What is special about plasmacytoid dendritic cells (pDCs)?
Have the ability to secrete large amounts of type 1 interferons upon activation through TLR7 and TLR9
Which lymphocytes are part of the humoral immune response, mature in the bone marrow, bind Ag and generate Ab?
B lymphocytes
3 major roles of antibodies
neutralization - bind virulence factors, pathogen cannot infect host cells
opsonization - (covers patho)- alerts neutrophils and macrophages to engulf and digest pathogen
complement activation - directly destroy or lyse pathogens. MAC.
Which lymphocytes mature in the thymus, are part of the cellular immune response?
T lymphocytes
2 categories of T cells
CD8+ - cytotoxic - kill infected or cancer cells
CD4+ - Helper T - (Th1, Th2, Th17, tregs)
Function of Th1 cells
coordinate immune responses against intracellular pathogens (viruses, bacteria, protozoa)
produce and secrete cytokines to activate macrophages
Function of Th2 cells
Coordinate immune response against extracellular pathogens (helminths)
Alert B cells, granulocytes and mast cells
Function of Th17 cells
produce interleukin 17, activating immune and non-immune cells
protect surfaces (skin, gut) against extracellular bacteria
recruit neutrophils and CDT+8 cytotoxic cells
summon immune strike against cancer
What do Tregs (regulatory T cells) do?
Monitor and inhibit activity of other T cells via inhibitory cytokines
Molecules that activate receptors and may be free-floating or membrane-bound
Ligands
Immune cells can dispatch specific instructions by altering the expression and density of what 2 things?
receptors and ligands
Small proteins involved in cell growth, activation, etc
cytokines
Function of Toll-like receptors (TLRs)
expressed on innate immune cells (macrophages and dendritic cells)
recognize microbial patterns, essential for innate immune cell activation and inflammatory responses
BCRs and TCRs recognize…
foreign antigens
C3a and C5 (complement) are chemoattractants that recruit what type of cell to inflammatory sites?
neutrophils
Areas of lymphoid production in fetus
yolk sac
fetal liver
omentum
Primary lymphoid organs (development)
bone marrow
thymus
Bursa of Fabricius
Secondary lymphoid organs (response)
speen
lymph nodes
Peyer’s patches
non-encapsulated lymphoid tissue
While T lymphocytes mature in the thymus, B lymphocytes can mature in what places depending on species?
Bursa- birds
Bone marrow- primates and rodents
Intestinal lymphoid tissue- rabbits, dogs, pigs
Which part of the thymus contains most of the thymocytes?
cortex
What are thymosins, thymopoietins, thymulin, and thymostimulins?
thymic hormones that work with cytokines to regulate maturation of T lymphocytes in the thymus
While maturing in the thymus, which thymocytes will be destroyed via apoptosis?
Thymocytes with receptors that bind strongly to self-antigens
Thymocytes that cannot bind MHC II molecules
Where is the Bursa of Fabricius found?
In birds only, before the cloaca. Each follicle has cortex and medulla. Cortex contains lymphocytes, plasma cells, macrophages.
Function of Bursa of Fabricius
Maturation and differentiation of Ab forming cells
Neg and Pos selection of B lymphocytes
Development timing of secondary lymphoid organs (capsulated and non-capsulated)
Develop late in fetal life
Persist into adult life
*surgical removal does not impair immune capability
Function of secondary lymphoid organs
DC’s trap and process Ag, and present them to lymphocytes
Things to know about lymph nodes
Filter lymph to trap Ag
Cortex contains B lymphocytes in germinal centers
Paracortex contains T cells and DCs
In what direction do afferent and efferent lymph vessels flow?
Afferent - into the node (carries lymphocytes, DCs and Ag)
Efferent - out of node
What is the principle function of lymph nodes?
Facilitate interaction between DCs and B/T lymphocytes. (so B and T cells find the correct antigen they were meant to react to)
2 types of tissue in the spleen
Red pulp - blood filtering and RBC storage
White pulp - lymphocytes, immune induction
Functions of the spleen
Filters blood for pathogens, debris, old blood cells
Stores RBCs, platelets
Recycles Fe++
Peyer’s Patches in the ileum are PRIMARY lymphoid organs (B cell development) in which species?
*secondary in other species
Ruminants
Pigs
Dogs
Rabbits
Function of M cells covering Peyer’s Patches
Sample Ag from the intestine and pass them into the germinal center so B lymphocytes can react
Peyer’s Patches undergo involution EXCEPT in these 2 species:
Rabbits and rodents
These non-encapsulated lymphoid aggregates line the mucosal surfaces of the body and make up a large portion of total lymphoid tissue
MALT
GALT - gastrointestinal
BALT - bronchial
NALT - nasal
CALT - conjunctiva
What is the best known mucosal-associated lymphoid tissue?
GALT
inductive site of intestinal immune response
effector site of intestinal immune response
What’s up with Innate Lymphoid Cells (ILCs)?
Cells that are of lymphoid origin but function as innate immune cells.
Don’t have BCR or TCR
Secrete high conc of cytokines
Localized to mucosal surfaces
3 groups
