Lecture 3/4 - Antigen Recognition, Processing & Presentation

Question 1

Epitope

Answer 1

Small part of Ag (peptide) recognized by MHC, T cell or B cell

Question 2

Langerhans cells/ Plasmacytoid Dendritic Cell

Answer 2

• Immature dendritic cells that reside in skin
• Phagocytotic, take in molecules for self/nonself determination
• Immature DC
• take in antigen and present it to t cell in lymyphatic system

Question 3

CD3: T Cell Receptor Complex

Answer 3

• Transmit signals to inside cell after TCR binds peptide/MHC
• provide communication to inside bc TCRs have short membrane chains
• e/d on one side of TCR, g/e on other side, z on innermembrane side
• CD3g or e deficiency = low numbers of receptors/impaired signalling
• CD3d or z chain deficiency = T cells absent, NK cells have impaired cytolytic functions

Question 4

Classical Dendritic Cell

Answer 4

• Antigen presenter function in lymph node

- Mature DC

Question 5

SLC

Answer 5

• Secondary Lymphoid tissue Chemokine

- Chemokine responsible for cell migration

Question 6

ELC

Answer 6

• Epstein-Barr Virus-induced molecule-1 Ligand Chemokine

- Chemokine responsible for cell migration

Question 7

HLA

Answer 7

• Human Leukocyte Antigens

- Present on leukocytes, cause issues w implants

Question 8

MHC

Answer 8

• Major Histocompatability Complex
• Genes that express HLAs
• 2 types: Autologous-self, Allogeneic- nonself
• Expressed by codominane to maximize number of MHC molecules expressed

Question 9

Balancing Selection

Answer 9

Tends to maintain a given polymorphism

Question 10

Directional Selection

Answer 10

Tends to introduce new halotypes (DNA variations, or polymorphisms, that tend to be inherited together)

Question 11

Polymorphism

Answer 11

Multiple alternative alleles w/in a population

Question 12

Polygeny

Answer 12

Multiple similar genes encoding the same proteins

Question 13

Immature DC vs Mature DCSecre

Answer 13

Immature: 
-Highly phagocytic
-Low levels of MHCII and CCR7 (Receptors for CCL32 or SLC and CCL19 or ELC, cell migration chemokines)
-Some B220 
-Smaller
Mature: 
-Lost phagocytic ability
-High levels of CCR7 and very high levels of MHCII = better chemokine response 
-Express CD80(B7.1) or CD86(B7.2) and CD40 (costimulatory molecules for T cell interaction) = better Ag presenting function
-Secrete CCL18 = attracts naive T cells
-More B220
-Larger

Question 14

MHC Class I (Components, Peptide Binding Groove, Location,

Expression Regulation, Ag Processing/Presentation)

Answer 14

Components: -3 a chains
-1 B2 microglobulin
Peptide Binding Groove: -Made by a1 and a2(both are variable)
-Closed end
- 8-10 residue peptide
Location: -Surface of every nucleated cell
Expression Regulation: -IFNy (from T cells/NK cells) -> turns on NLRC5 -> turns on MHC I genes
Ag Processing/Presentation: -Endogenous processing (proteins made in cell)
-CD4 + T cells
-Reports self and nonself peptides

Question 15

MHC Class II

Answer 15

Components: -2 a chains 
-2 B chains
Peptide Binding Groove: -Made by a1 and B1 (only B1 is variable)
-Open ended
-11-30 residue peptide
Location: -3 different APC cells  
-Pros: DC 
-Semipros: B cells, Macrophages
Expression Regulation:  -IFNy (from T cells/NK cells) -> turns on NLRC5 -> turns on CIITA -> turns on Class II genes
Ag Processing/Presentation: 
-Exogenous processing (proteins from outside of cell)
-CD8 + T cells
-Reports Ag only