Cells and Tissues - Lecture 2

Question 1

Where do WBC migrate?

Answer 1

some naturally migrate into tissues, others remain in blood until therei s inflammation or tissue injury

Question 2

When are macrophages activated?

Answer 2

only when bound to by Ab-Ag complex

Question 3

Describe features of eosinophils

Answer 3

• also PMN
• low numbers
• migrate to spleen where they mature, then migrate into tissues
• responsible for phagocytosis and killinf of parasites
• have Fc receptors –> bind antibodies
• contain bi-lobed nuclei and cytoplasmic granules
• granules contain aicd phosphatase, perioxidase and toxic proteins
• life span: 12 days

Question 4

When are eosinophils really important?

Answer 4

in environments with high amounts of parasites

Question 5

When can eosinophils be more harmful?

Answer 5

in hygienic environments

Question 6

How does binding work with eosinophil?

Answer 6

antibody must bind first to parasite then eosinophil can bind to antibody

Question 7

Describe features of basophils

Answer 7

• also PMN, low numbers
• contain multi-lobed nucleus
• cytoplasmic granules
• granules contain inflammatory molecules, including vasoactive amines (histamine, serotonin)
• not normally distributed in tissues
• play a role in killing of parasites due to presence of FceRI

Question 8

Describe features of mast cells

Answer 8

• contain multi-lobed nucleus
• long-lived (weeks) after distribution into tissues (primarily CT and near body surfaces, reside near blood vessels)
• have different morphologies in different tissues
• play a role in killing of parasites due to presence of FceRI
• cytoplasmic granules contain inflammatory molecules including amines (histamine, serotonin)
• must bind Ab first before pathogen

Question 9

Describe binding with NK cells

Answer 9

Ag binds Ab, then NK binds, release contents

Question 10

What are key features of adaptive immunity?

Answer 10

-specific to given molecule (epitope), mediated by lymphocytes, have surface receptors for Ag, specific immunity to Ag, provide memory of specific Ag

Question 11

What are the two types of lymphocytes?

Answer 11

B and T cells

Question 12

What do b cells produce?

Answer 12

antibodies (humoral) –> bind Ag; also interact with components of innate immunity

Question 13

What do T cells do?

Answer 13

recognize processed Ag on host cells (cell-mediated)

Question 14

What types of T cells?

Answer 14

Helper T cell, cytotoxic T cells

-differentiation occurs after exposed to Ag

Question 15

What do helper T cells do?

Answer 15

activate or regulate activities of other cells (make cells better at what they do

Question 16

What do cytotoxic T cells do?

Answer 16

kill host cells bearing a foreign antigen (cancerous, viral-infected)

Question 17

What is clonal selection?

Answer 17

once selected, lymphocytes undergo clonal replication; selection is based on an individual cell having the correct receptor for a very small defined part of a larger antigen; other cells of same type with different receptors are NOT activated

Question 18

Where are the receptors found?

Answer 18

encoded int he genome of the organism, but in B and T cells, the genome rearranges “randomly”. Generates cells of the same type but with different receptors

Question 19

Which cells undergo clonal selection?

Answer 19

B and T cells - antigen specific

Question 20

What does clonal selection ensure?

Answer 20

only cells with receptors against a foreign antigen are activated ; B cells –> Ab but require help from Ag-specific T cells; some other types of T cells –> directly kill any cell with foreign Ag on its surface

Question 21

What are lymphoid organs?

Answer 21

sites where lymphocytes develop and/or contact and respond to specific antigens; points of differentiation, antigen and immune cell collection and adaptive immune response

Question 22

What do lymphocytes interact with in lymphoid organs?

Answer 22

non-lymphoid cells (stromal cells)

Question 23

What happens in primary vs secondary lymphoid organs?

Answer 23

primary - differentiation
secondary - activation
some tissues can be primary and secondary

Question 24

Describe primary lymphoid organs

Answer 24

sites of production and differentiatino for lymphocytes; provide a network of stromal fibroblasts and fat cells with which precursors interact to signal developemtn

Question 25

Name primary lymphoid organs

Answer 25

bone marrow or bursa, thymus, peyer's patches (b cells esp in ruminants)

Question 26

Describe bone marrow/bursa

Answer 26

sites of early lymphocyte development in mammals and birds; T cells --> thymus; B cell receptor rearrangement occurs in marrow/bursa; also secondary lymphoid organs

Question 27

What happens if excessive blood cell production is demanded?

Answer 27

liver and spleen can serve as sites for lymphocyte production

Question 28

Describe bone marrow

Answer 28

- site of hematopoiesis and also a site where mature b cells reside - stromal cells support lymphopoiesis and myelopoiesis via surface ligands and secretion of certain cytokines/GF - proportion of each cell produced depends on signal received in bone marrow

Question 29

Whats the function/features of the thymus?

Answer 29

naive or immature T cells leave bone marrow and migrate here to complete maturatino - located in upper anterior thorax - consists of many lobules of loosely packed epithelial cells - presentation of self antigens only - involutes after sexual maturity - T cells don't differentiate until thymus whereas B cells elave bone marrow committed to certain type

Question 30

What is the morphology of thymus?

Answer 30

- hassall's corpuscle - role in tolerance - cortex - densely packed with immature T cells - medulla - less dense collection of mature lymphocytes - trabuculae - divide into lobes

Question 31

What are peyer's patches

Answer 31

structures along Gi tract within lamina propria - contain large numbers of lymphocytes and b cells - arranged in follicles iwth b cells central and T cells surrounding them - important for immune response for ingested Ag - B cells mature here - more important in ruminants - take up Ag from gut and transport to draining lymph nodes

Question 32

What are germinal centers?

Answer 32

site where B cells are rapidly dividing

Question 33

What are m cells?

Answer 33

in the mucosal lining are sites of antigen entry but immune cells in peyer's patches take them up

Question 34

Describe secondary lymphoid organs

Answer 34

sites where lymphocytes devlelop and/or contact and respond to specific Ag; essentially collection and response points -tonsils, spleen, lymph nodes, peyer's patches, bone marrow

Question 35

Describe the spleen

Answer 35

- secondary lymphoid organ - largest lymphoid organ - compartmentalized structure in a thick capsule - red pulp --> phagocytes - white pulp --> lymphocytes - mostly b cell, but also Tells - major site of adaptive immunity to blood-borne pathogens - filters out effected RBC and also stores RBCs `

Question 36

What makes up white pulp?

Answer 36

all of the lymphocytes collectively arranged along blood vessels as well as plasma cells, macrophages --> immune responses

Question 37

What are the two components of white pulp?

Answer 37

``` splenic nodules (lymph nodes) - contain B lymphocytes -periarterial lymphatic sheaths - T lymphocytes ```

Question 38

What happens if you remove the spleen?

Answer 38

technically there would be a dec in immunity but there's lots of redundancy and overlap in immune system so not a big deal

Question 39

Describe features of lymph nodes

Answer 39

- highly organized encapsulated structures - points of convergence for cells in blood and lymph systems - collects extracellular fluid (lymph) from tissues for return to blood - contain B and T cells in segregated regions

Question 40

Where are T and B cells located in lymph nodes?

Answer 40

B cells - mostly in cortex | T cells - mostly in medulla

Question 41

What's the structure of lymph nodes?

Answer 41

bean-shaped, divided into outer cortex and inner medulla, surrounded by capsule - vessels enter and/or leave the node via hilus - dendritic cells and lymphocytes can enter from afferent lymphatic or from blood

Question 42

What happens when you are sick?

Answer 42

lymph nodes swell, large collection of lymph as well as B cells proliferating rapidly

Question 43

What happens as a result of somatic mutation?

Answer 43

occurs in germinal centers - start to make better antibodies that bind epitope better/stronger

Question 44

What's cell migration into lymph nodes?

Answer 44

lymphoctyes and dendritic cells enter lymph nodes by different routes. most lymphocytes enter from peripheral blood. Only lymphocytes can interact with and extravasate through high endothelial venules (HEVs) to migrate into lymph node parenchyma. - T and B cells segregate into T and B cell zones - most DCs (with small number of lymphocytes) enter through afferent lymphatics. They then accumulate in viccinity of HEVs

Question 45

What are HEVs?

Answer 45

High endothelial venules - specialized capillaries of lymphoid tissues (all secondary lymphoid organs) where lymphocytes exchange from blood. Endothelial cells in HEV lack tight junctions. Most T cells in lymph node enter via blood