Ontogeny of the Immune System (complete) Flashcards
Define stem cell
- Undifferentiated cells
- When they divide, give rise to another stem cell and a more differentiated daughter cell
Define B cell
- Lymphocytes
- Play large role in humoral immune response
- Make Abs
- Develop in bone marrow
Define T cell
- Lymphocytes
- Play central role in cell-mediated immunity
- Have T cell receptors
- Mature in thymus
Define pre-B cell
A B cell w/ cytoplasmic IgM — no surface IgM
Define pre-T cell
- 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
Define self-tolerance
process by which the body does not mount an immune response to self-antigens
Define titer
Measures the level of Abs in a blood sample
Outline the process of B cell maturation. Indicate locations
HSC –> common lymphoid progenitor –> pro-B –> pre- B –> immature B –> mature B
all in bone marrow
Outline the process of B cell maturation. Indicate locations
HSC (BM)–> common lymphoid progenitor (BM) –>pre-T (BM) –> immature T (thymus) –> mature T (move to lymph)
Define Bursa of Fabricus
Where BM precursors go to finish their development
IN BIRDS
What is the equivalent of Bursa of Fabricus in mammals?
Bone marrow
Describe the sequence of appearance of cytoplasmic and surface immunoglobulins in developing B cells
- 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
Describe clonal deletion of B cells
- If immature Bs exposed to Ag, signal causes cell to try receptor editing
- If this fails, activates apoptosis
Process regulates anti-self lymphocytes
Draw a graph showing Ab response to a typical antigen in 1ary and 2ary response
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)
What happens to Ab response to a typical antigen in a person has no functional T cells?
No IgG production
Only regular IgM response
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
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
What is the half life of IgG?
3 weeks
When and why is a baby’s immune system most vulnerable?
In the first 6 months
Mom and baby’s IgG levels are low
WHY BREASTFEEDING IS SO IMPORTANT!
Given a newborn’s Ab titer, interpret significance if Ab is IgG or IgM
If IgM: we know that baby made it and baby was exposed to something (Mom’s can’t cross placenta)
If IgG: from mom
What will the titer of IgG be at 4 months of age?
half-life: 3 weeks
4 months ~= 16 weeks
Answer: about 2.5% (between 15 and 18 week markers)
Discuss the decrease in diversity seen in immune response of the elderly
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)
