Human Immune System

Question 1

hematopoietic stem cells result in myeloid progenitor cells that give rise to _______________ immune cells (5)

Answer 1

neutrophils
eosinophils
basophils
dendritic cells
macrophages
mast cells

Question 2

what role do neutrophils have?

Answer 2

they are the most abundant WBC

primary mediators of the rapid innate immune system vs bacterial and fungal pathogens

Question 3

what does elevated neutrophils tell you?

Answer 3

most likely caused by infection or some sort of high stress – neutrophilia or neutrophilic leukocytosis

Question 4

what role does eosinophils have?

Answer 4

specialized WBC (granulocyte; release highly toxic proteins and free radicals) for parasites and certain allergic diseases

Question 5

what does elevated eosinophils tell you?

Answer 5

parasitic infection or certain allergic reactions like asthma, allergic rhinitis, and dermatitis

less common: certain blood cancers and eosinophilic granulomatosis with polyangitis

Question 6

what role does basophils have?

Answer 6

least common WBC
granulocyte
involved in acute and chronic allergic diseases

can also play a role in parasitic infections

Question 7

what does elevated basophils tell you?

Answer 7

infection, allergic disease attack, cancer like leukemia or an autoimmune disease

Question 8

role of dendritic cells?

Answer 8

activate T cells and initiate adaptive immune response

Question 9

role of macrophages?

Answer 9

phagocytosis, can activate T cells in the tissues

Question 10

role of mast cells

Answer 10

release certain immune response mediators esp in response to bacteria, parasites, and allergies

ex. histamine, heparin, cytokines, and growth factors

Question 11

in general, what is the lymphatic system?

Answer 11

its a network of vessels throughout the body that results in the movement of lymphatic fluids up towards two drainage points above the heart (subclavian veins)

lymph capillaries interact with blood capillaries so fluids from the tissues can be drained into the lymph

Question 12

what is the role of lymph nodes and the spleen?

Answer 12

the police station for the adaptive immune system

place where B and T cells can hang out to wait to be activated by DCs and macrophages

Question 13

what is the main role of the innate immune system?

Answer 13

first line defence; brings non-specified immune cells and inflammatory mediators to the site of invasion

Question 14

is the innate immune system a fast or slow response?

Answer 14

fast, within minutes

Question 15

how does the innate immune system recognize pathogens?

Answer 15

via PAMPs - pathogen-associated molecular patterns that are highly conserved components of pathogens for their virulence

the immune system has PPRs - pattern recognition receptors

Question 16

what is the basic overview physiology of an innate immune response?

Answer 16

1. effector cells recognize using PRRs via PAMPs
2. triggers the complement system
3. complement results in an increase in cytokines + vasodilation + increased vascular permeability
4. also results in phagocytosis or MAC complex
5. tissue becomes inflammed

Question 17

what is the role of the complement system?

Answer 17

it’s a mechanism to recruit and activate cellular immune responses that can participate in killing the pathogen

Question 18

name the three pathways to activate the complement system

Answer 18

1. classical - antigen-antibody complex
2. alternative - bacterial endotoxin
3. lectin - specific glycoproteins

Question 19

what are complement proteins and where are they synthesized?

Answer 19

they are proteins involved in the complement system activation that are found in the blood, lymph, and ECF

most are produced in the liver and circulate in their inactive forms

Question 20

what are the end results of complement system activation?

Answer 20

there is a recruitment of inflammatory mediators, phagocytes and anaphylatoxins that increase vascular permeability

there is complement fixation ➔ opsonization ➔ enhances phagocytosis

finally, there is the formation of membrane attack complex (MAC) which forms a pore in the pathogen membrane which results in cell death

Question 21

what is the main role of the adaptive immune system?

Answer 21

it’s an antigen-specific response to a foreign antigen/pathogen that can be long lasting

consists of both cellular an humoral immunity

Question 22

what effector cells are most involved in the innate immune system?

Answer 22

leukocytes like neutrophils, eosinophils, basophils, DCs, macrophages, and mast cells

may also involved NK cells

Question 23

what effector cells are most involved in the adaptive immune system?

Answer 23

B cells and T cells (CD4 and CD8)

Question 24

what physical barriers could we also consider a part of the innate immune system? (3)

Answer 24

skin, saliva, mucous membranes

Question 25

what chemical barriers could we also consider a part of the innate immune system? (5)

Answer 25

urine pH, vaginal pH, stomach acid, tears, ROS

Question 26

what microbiological barriers could we also consider a part of the innate immune system? (3)

Answer 26

gut flora, vaginal flora, skin flora

Question 27

what physiologic barriers could we also consider a part of the innate immune system? (2)

Answer 27

cough reflex, fever - denatures proteins

Question 28

what are the two primary lymphoid organs? what are their functions?

Answer 28

bone marrow
thymus

both are where B and T cells mature into their naive forms until being released to the secondary lymphoid organs for activation

Question 29

what are secondary lymphoid organs?

Answer 29

Lymph nodes, spleen, peyer’s patches, and mucosal and nasal associated lymphoid tissues, adenoids, and tonsils

Question 30

what is the function of secondary lymphoid organs?

Answer 30

provide an environment for the proliferation and maturation of B and T cells in response to exposure whilst also filtering and trapping antigens from the hematogenous circulation

Question 31

how are naive T cells developed?

Answer 31

1. common lymphoid progenitor cell in bone marrow
2. becomes a T cell precursor in the thymus
3. development of TCR via VDJ recombination
4. maturation of T cells - positive selection (functional TCR) and negative selection (remove self-reactive TCR)
5. naive CD4+ and CD8+ T cells developed and circulate in the lymphatic system until activation

Question 32

how are naive B cells developed?

Answer 32

1. common lymphoid progenitor cell in bone marrow
2. VDJ recombination to create BCR
3. positive selection - functional BCR
4. negative selection - self-tolerance mechanisms if self-reactive ➔ receptor editing, clonal deletion, or becoming anergic
5. naive B cells circulate searching for infection

Question 33

how does cellular immunity work/happen?

Answer 33

1. pathogen entry
2. antigen-presenting cell ➔ MHC I on all nucleated cells ➔ activates CD8+ cytotoxic T cells
3. direct pathogen killing

Question 34

how does humoral immunity work/happen?

Answer 34

1. pathogen entry
2. antigen-presenting cell ➔ directly to B cell receptor ➔ activate into plasma cell ➔ antibodies

OR MHCII on DC or macrophages ➔ activates CD4+ helper T cells ➔ activates B cells ➔ clonal expansion ➔ plasma cells ➔ antibodies
*can also activate cytotoxic CD8+ T cells

plasma cells become memory B cells

Question 35

what is the function of the spleen for the immune system?

Answer 35

white pulp - filtered blood ➔ allows for activation of B and T cells
- important for the detection and opsonization of encapsulated bacteria

red pulp - removal of damaged/old RBCs, acts as storage of RBCs and plts that can be used in cases of emergency

Question 36

what are 3 examples of encapsulated bacteria?

Answer 36

Streptococcus pneumoniae
Haemophilus influenzae
Neisseria meningiditis

Question 37

how do antibodies work in an infection?

Answer 37

• neutralize the pathogen to prevent adhesion
• opsonize the pathogen for macrophage
• complement activation