Exam 1: Organs of the Immune System

Question 1

Lymphocytes

Answer 1

Arise from stem cells in bone marrow - mature in primary lymphoid organs

Question 2

Self antigens

Answer 2

If lymphocytes have receptors for self antigens - could cause tissue damage –> killed before leave primary lymphoid tissue

Question 3

Difference between primary and secondary lymphoid tissue

Answer 3

Primary - site of lymphoid development

Secondary - site of response to antigens

Question 4

Can divide lymphoid organs into 3 groups

Answer 4

1. Sources of lymphocytes: yolk sac –> fetal liver –> bone marrow
2. Primary: thymus, bursa, Peyer’s patches, bone marrow
3. Secondary: tonsils, spleen, Peyer’s patches, bone marrow, lymph nodes

Question 5

Primary lymphoid organ characteristics:
Origin
Time of development
Persistence
Effect of removal
Response to anitgen

Answer 5

Origin: ectodermal junction or endoderm

Time of development: early in embryonic life

Persistence: involutes after puberty

Effect of removal: loss of lymphocytes

Response to antigen: unresponsive

Question 6

Secondary lymphoid organ characteristics:
Origin
Time of development
Persistence
Effect of removal
Response to anigens

Answer 6

Origin: mesoderm

Time of development: late in fetal life

Persistence: persists in adults

Effect of removal: no or minor effects

Response to antigen: fully reactive

Question 7

Athymic animals

Answer 7

Born without a thymus

Animal is usually hairless

However lack of hair does not always equal no thymus

But lack of thymus always equals no hair

More susceptible to infectious diseases

More susceptible to cancer

Must live in sterile environment

Question 8

Effects of neonatal thymectomy (7)

Answer 8

Number of circulating lymphocytes: disappear

Presence of lymphocytes in T-dependent areas: disappear

Graft rejection: suppressed

Presence of lymphocytes in T-independent areas: minor depletion

Plasma cells in lymphoid tissue: minor drop

Serum immunoglobulins: minor drop

Antibody formation: minor effects

Question 9

Effects of neonatal bursectomy (7)

Answer 9

Number of circulating lymphocytes: no effect

Presence of lymphocytes in T-dependent areas: no effect

Graft rejection: no effect

Presence of lymphocytes in T-independent areas: disappear

Plasma cells in lymphoid tissue: disappear

Serum immunoglobulins: major drop

Antibody formation: major drop

Question 10

Peyer’s patches: ruminants, pigs, horses, dogs, humans

Answer 10

Large band in ileum and smaller patched in jejunum

Question 11

Lymphocyte recirculation

Answer 11

Lymphatic fluid gets recirculated through lymphatic system

Question 12

Immune surveillance

Answer 12

Recirculation of B ad T cells and dendritic cells

Part of lymphocyte recirculation

Question 13

Why do dendritic cells recirculate

Answer 13

If dendritic cells can’t find specific B and T cells to react with the dendritic cells migrate to a different lymph node so it can find B and T cells to react with

Question 14

Lymphatics

Answer 14

System of open ended vessels that return extravascular fluid from the periphery to the hearth and blood

Question 15

Lymph nodes

Answer 15

Distributed throughout lymphatics, small filtering stations

Question 16

Peyer’s patches: Primates, rabbits, rodents

Answer 16

Small patches in both jejunum and ileum

Question 17

Where do B cells mature

Answer 17

B cells mature in bone marrow

Question 18

Where do T cells mature

Answer 18

T cells mature in thymus

Question 19

Athymic animals: nude mouse vs Mexican hairless dog

Answer 19

Nude mouse - bred for lab, only lives in labs, must live in sterile environment –> no thymus

Mexican hairless dogs - live in normal environment –> so most likely has a thymus