Chapter 3: Lymphocyte Development and Selection Flashcards
The mature naive B lymphocyte expresses what 2 isotypes within its surface membrane?
IgM and IgD
What receptor on the B cell does EBV bind to?
CD 21
mRNA molecules are created which join variable domains to what type of constant domains in B cell heavy chains?
mu or delta
Order with which VDJ combination takes place in heavy chains?
- D-J joining
- V-DJ joining
What does VDJ stand for?
variable, diversity, joining
Order VDJ recombination takes place in light chains?
V-J joining thats it really
Which chain on T cell receptor is synonymous with the B cell heavy chain?
beta
Which on TCR is synonymous with the B cell light chain?
alpha
What type of constant chain domains do the light chain bind to?
kappa or lamda
Purpose of Tdt?
While heavy chain gene segments undergo recombination, this enzyme, terminal deoxyribonucleotidyl transferase, randomly inserts bases (without a template on the complementary strand) > junctional diversity
Allelic exclusion?
When recombination has generated a functional product then allele on homologous chromosome is turned off.
Difference between N-nucleotide addition in B and T cells?
B cells (only heavy chains)
T cells (all chains)
RAG 1 and RAG 2
2 proteins found within recombinase, a protein complex
Resoposbile for B and T cell rearrangment to create functioning receptors on the surface
What is the inheritance pattern of Omenn Syndrome?
AR
Inheritance pattern of SCID?
severe comibined immunodeficiency is an AR condition can also be X-linked
Omenn Syndrome molecular defect?
- missense mutation in RAG genes
- the RAG enzymes have only partial activity
Symptoms of Omenn Syndrome?
- Lack of B cells (below limits of detection)
- marked decrease in predominantly Th2
*characterized by early onset, failure to thrive, red rash (generalized), diarrhea, and severe immune deficiency
What is the molecular defect in SCID?
- null mutations in RAG1 or RAG 2 genes
- no RAG enzyme activity
What are the symptoms of SCID?
- total lack of B and T cells
- total defects in humoral and cell-mediated immunity
Is bone marrow considered a primary or secondary lymphoid organ?
primary lymphoid organ
B lymphocytes whose idiotypes have too great an affinity for normal cellular molecules go through what processes?
- They are either deleted in the bone marrow (clonal deletion)
- They are inactivated in the periphery (clonal anergy)
How does clonal anergy take place?
anergic B cells express high levels of IgD on their surface rendering them inactive