Ontogeny of the Immune System (complete)

Question 1

Define stem cell

Answer 1

• Undifferentiated cells

- When they divide, give rise to another stem cell and a more differentiated daughter cell

Question 2

Define B cell

Answer 2

• Lymphocytes
• Play large role in humoral immune response
• Make Abs
• Develop in bone marrow

Question 3

Define T cell

Answer 3

• Lymphocytes
• Play central role in cell-mediated immunity
• Have T cell receptors
• Mature in thymus

Question 4

Define pre-B cell

Answer 4

A B cell w/ cytoplasmic IgM — no surface IgM

Question 5

Define pre-T cell

Answer 5

• Found in bone marrow
• Don’t have characteristic surface markers to distinguish them — Committed to expressing them in right environment
• Develop in bone marrow and go to thymus

Question 6

Define self-tolerance

Answer 6

process by which the body does not mount an immune response to self-antigens

Question 7

Define titer

Answer 7

Measures the level of Abs in a blood sample

Question 8

Outline the process of B cell maturation. Indicate locations

Answer 8

HSC –> common lymphoid progenitor –> pro-B –> pre- B –> immature B –> mature B

all in bone marrow

Question 9

Outline the process of B cell maturation. Indicate locations

Answer 9

HSC (BM)–> common lymphoid progenitor (BM) –>pre-T (BM) –> immature T (thymus) –> mature T (move to lymph)

Question 10

Define Bursa of Fabricus

Answer 10

Where BM precursors go to finish their development

IN BIRDS

Question 11

What is the equivalent of Bursa of Fabricus in mammals?

Answer 11

Bone marrow

Question 12

Describe the sequence of appearance of cytoplasmic and surface immunoglobulins in developing B cells

Answer 12

• Pro-B cells begin to make detectable mu chains
• Pre-B make cytoplasmic IgM
• immature B have surface IgM
• mature B have surface IgM and IgD

Question 13

Describe clonal deletion of B cells

Answer 13

• If immature Bs exposed to Ag, signal causes cell to try receptor editing
• If this fails, activates apoptosis

Process regulates anti-self lymphocytes

Question 14

Draw a graph showing Ab response to a typical antigen in 1ary and 2ary response

Answer 14

1ary: IgM secreted first — helper T cells help B cells switch to IgG (higher response)
2ary: IgM response same as 1ary — IgG is sooner, faster, higher, more prolonged than 1ary (think memory)

Question 15

What happens to Ab response to a typical antigen in a person has no functional T cells?

Answer 15

No IgG production

Only regular IgM response

Question 16

Draw a graph which shows relative IgG and IgM levels in a normal infant from conception to 1 yo — distinguish between maternal and infant Abs

Answer 16

See notes for actual graph

Conception: baby makes IgM (IgM can’t cross placenta) — Mom tranfers IgG

Birth: Baby has 100% adult levels, but drops

2-3 m: baby makes IgA

3-6 m: baby makes IgG

Question 17

What is the half life of IgG?

Answer 17

3 weeks

Question 18

When and why is a baby’s immune system most vulnerable?

Answer 18

In the first 6 months

Mom and baby’s IgG levels are low

WHY BREASTFEEDING IS SO IMPORTANT!

Question 19

Given a newborn’s Ab titer, interpret significance if Ab is IgG or IgM

Answer 19

If IgM: we know that baby made it and baby was exposed to something (Mom’s can’t cross placenta)

If IgG: from mom

Question 20

What will the titer of IgG be at 4 months of age?

Answer 20

half-life: 3 weeks

4 months ~= 16 weeks

Answer: about 2.5% (between 15 and 18 week markers)

Question 21

Discuss the decrease in diversity seen in immune response of the elderly

Answer 21

up to 40yo, people can reconstitute their T cell #s and diversity

as you age, more and more memory phenotype present due to lifetime of exposure

Not a lot of naive cells — don’t do well w/ new diseases (e.g. SARS)