Antigen Presenting Cells (APCs)
367
Tab. 4
Self-peptides eluted from the class II molecule HLA-DR4 of human monocyte-derived
dendritic cells, stimulated with TNF-
α
.
Antigen
Sequence
P1
P4
P6
HLA-B60
D
T
Q
F
V
R
F
DS
D
A
A
SQRM
HLA-B60
D
T
Q
F
V
R
F
DS
D
A
A
SQR
HLA-B60
T
Q
F
V
R
F
DS
D
A
A
SQR
HLA-B60
Q
F
V
R
F
DS
D
A
A
SQR
HLA-B60
F
V
R
F
DS
D
A
A
SQR
HLA-B60
F
V
R
F
DS
D
A
A
SQRMEP
β
2m
YLL
Y
YT
E
F
T
PTEKDE
β
2m
LL
Y
YT
E
F
T
PTEKDE
Mannose receptor
F
E
N
K
W
YA
D
C
T
SAGRSDG
Calreticulin
D
N
P
E
Y
SP
D
P
S
IYAYDN
Transferrin receptor
T
G
Q
F
L
YQ
D
S
N
WA S K Y
Apolipoprotein d
V
L
N
Q
E
L
RA
D
G
T
VNQ I EG
Apolipoprotein d
L
N
Q
E
L
RA
D
G
T
VNQ I EG
Apolipoprotein d
Q
E
L
RA
D
G
T
VNQ I EG
IL-10 receptor
D
K
L
S
V
IA
E
D
S
ESGKQNPG
Rab-7
F
P
E
P
I
KL
D
K
N
DRAKASA
Rab-7
F
P
E
P
I
KL
D
K
N
DRAKAS
Rab-7
F
P
E
P
I
KL
D
K
N
DRAKA
Anchor motif
FD
A
YE
T
WS
IN
L
V
phosphatidylinositol
mannosides,
and
hexosyl-1-phosphoisoprenoids to cytotoxic
T cells. These ligands are derived either
from internalized mycobacteria or from
the uptake of lipoarabinomannans by the
mannose receptor expressed on the sur-
face of monocytes and dendritic cells.
No naturally processed bacterial antigens
have been identiFed in the context of
the group II molecule CD1d molecule,
which is expressed in both humans and
mice. CD1d molecules present bacterial
α
-galactosylceramide to NK T cells. The
relationship between the peptide- and
lipid-binding capacities of CD1 is not clear,
as yet. Structural studies show that CD1
molecules bear a deep and hydrophobic
ligand-binding cleft in which glycolipids
bind – it is open whether peptides asso-
ciate to the same site (±ig. 4).
Compared to MHC class I and class
II molecules, CD1 proteins appear to
represent a separate lineage of antigen-
presenting molecules specialized in pre-
senting microbial lipids, glycolipids, and a
subset of peptide antigens to T cells.
6
Antigen Processing by APCs
Virus-infected cells can be destroyed by
CD8
+
cytotoxic T cells provided that the
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