Week 4 Flashcards
What do early pro B cells express? Intermediate? Late?
Early- TdT alone
Intermediate- both TdT and B220
Late- B220 and down regulated TdT
What 2 cytokines allow inflammatory cell recruitment?
IFN-gamma
TNF-alpha
What molecule modulates exchange for CLIP and antigenic peptide in MHC class 2 formation? What molecules blocks until acidic conditions?
HLA DM facilitates exchange
-HLA DO blocks DM (DO is only expressed in B cells and in thymus- helps DM only work in late endosome)
What enzyme is mutated in XLA immunodeficiency?
Bruton’s tyrosine kinase (Btk)
What ligand and receptors are mutated in Common Variable Immunodeficiency (CVID)?
CD40 ligand on T cells, B cell surface receptor CD19, activated T cell co-stimulatory molecules ICOS and TACI
Binding of what receptor on the T cell with B7 on APC is stimulatory? inactivating?
- stimulatory= B7 with CD28
- inactivating= B7 with CTLA-4
What cells express MHC class 1? MHC class 2?
- MHC class 1- most cells in body (except RBCs)
- MHC class 2- professional APCs (DCs, macrophages, B cells)
When do DCs, macrophages, B cells express MHC-class 2? (constantly, induced, etc)
- DCs: constituitively express MHC-2 (also always express B7)
- Macrophages: must be activated to express MHC class 2 and co-stimulatory molecules
- B cells: constitutively express Class 2; must be activated to express co-stimulatory molecules
What MHC class is loaded by the cytosolic pathway?
-MHC class 1 (synthesized in RER; TAP1/2 to enter ER)
What MHC class is loaded by the endocytic pathway?
-MHC class 2
What is the normal ratio of CD4: CD8 T cells in the body?
~65% CD4 and ~35% CD8
What age does MHC class 1 deficiency affect patient? Susceptible to what infections?
- young (age 4)
- susceptible viral infections: influenza, EBV
What age does MHC class 2 deficiency affect patient? (inherited autosomal recessive) Susceptible to what infections?
- onset 6 months
- mild form SCID (makes few T cells)
- elevated WBCs (esp. neutrophils and lymphocytes)
- low CD4+ T cells
- no HLA-DQ or HLA-DR being formed
- susceptible to pyogenic and opportunistic infections
How does classic SCID differ from milder form in case?
- classic SCID: no T cells responding to any antigen
- milder form: T cells could be activated in vitro by PHA
Is there a treatment for MHC class 1 deficiency? Class 2?
- MHC class 1 deficiency- no
- MHC class 2 deficiency- hematopoietic stem cell transplant
What cytokine induces expression of MHC class 2 molecules on APC?
Interferon- gamma
What are the cytokines required for B cell development?
- IL-7: promotes B cell lineage development
- Blys: survival of pre-immune B cells
- IL4, IL3, L-BCGF: initiating B cell differentiation
Transitional immature B cells: Which receptor on surface for TI-1? TI-2? where do they help B cell go?
- TI-1: transitional phase with IgM (T cell zone); negative selection
- TI-2: transitional phase with IgM and IgD (go to follicle); positive selection
T-independent B cell activation: Which antigens are TI-1 antigens? TI-2?
-many TI antigens are PAMPs (recognized by TLRs)
- TI-1: bacterial cell wall components; LPS (TLR4 or BCR)
- TI-2: large polysaccharide molecules with repeating antigenic determinants (Ficoll, dextran, polymeric bact. flagellin, poliomyelitis virus)
- activate B1 B cells
Which TLR causes nonspecific (polyclonal) activation?
Which receptor causes specific (clonal) activation?
- TLR4= polyclonal
- BCR= clonal
- only IgM is produced
How do B1 B cells bind Type 2 TI antigen? What type of activation?
- crosslinking BCR
- specific (clonal) activation
- mostly IgM produced
Expression of what CD molecule can identify B-1 cells?
-CD5
Where do B and T cells that recognize each other go? What does B cell need to express to survive?
- go to germinal centers
- B cell must express Bcl-2 (to protect itself from apoptosis)
What does CD44 do in T cell development?
-CD44 is required for re-localization to the thymus