Lecture 21: Antigen Capture and Presentation

Question 1

Class I MHC genes

Answer 1

• encoded by 3 different regions in locus
  
  • HLA-A/B/C
• on all NUCLEATED CELLS
• present to Cytotoxic T-Lymphocytes
• inhibitory receptor for NK cells

Question 2

Class I MHC structure

Answer 2

• heterodimer of two proteins

1. alpha chain (MHC encoded)
   
   • membrane bound glycoprotein
2. beta2 microglobulin (non MHC encoded)
   
   • associates non-covalently with alpha3

Question 3

Class II MHC genes

Answer 3

• encoded by HLA-D region
  
  • membrane bound glycoproteins
• on antigen-presenting cells
• presents to CD4+ T cells

Question 4

HLA peptide binding

Answer 4

• low affinity interaction (slow on rate, very slow off rate)
• allows complex time to interact with T-lymphocytes

Question 5

H-Y (minor MHC/HLA)

Answer 5

• coded on Y chromosome

- associated w/acute rejection of male grafts in female recipients

Question 6

What domains on the MHCI/II complexes do CD8 and CD4 recognize?

Answer 6

CD8 –> binds to alpha3 domain on MHCI

CD4 –> binds to beta2 domain on MHCII

Question 7

What T cells do dendritic cells, macrophages, and B lymphocytes present to?

Answer 7

DC –> naive T cells (initiation of T cell responses to protein antigens)

Macrophages –> CD4+ effector T cells (effector phase of cell-mediated immune response)

B lymphocytes –> CD4+ T helper cells (humoral immun response)

Question 8

Plasmacytoid Dendritic Cells

Answer 8

• found in blood/tissue
• promote innate anti-viral state (produce Type 1 interferons)
• expresses TLR 7 and 9

Question 9

Dendritic Cell Activation

Answer 9

• lose adhesion markers and upregulate CCR7
• inc. MHC and CD80 expression
• travels to 2nd lymphoid tissue
• mature as migrate

Question 10

Ankylosing Spondylitis

Answer 10

• spine inflammation
• 88% express HLA-B27 allele
  • cannot bind critical antigenic peptide

Question 11

Rheumatic Fever

Answer 11

• Abs for streptococci cross react with cardiac tissue

- patients w/HLA-DR4 more likely to develop

Question 12

Bare Lymphocyte Syndrome

Answer 12

• TAP protein nonfunctional, peptides can’t enter ER
• cells cannot present antigens
  symptoms: chronic respiratory infections, poor responses to viruses

Question 13

Bare Lymphocyte Syndrome Class II

Answer 13

• inherited defect in CIITA (deficiency in HLA Class II expression, non-functioning T lymphocytes)
• HLA II genes turned on by CIITA, RFX5, RFXAP, RFXANK
• mutations in these Transcription Factors lead to dec. expression of Class II gene products