Primary deficiency of microsomal triglyceride transfer protein in human abetalipoproteinemia is associated with loss of CD1 function.
Abetalipoproteinemia (ABL) is a rare Mendelian disorder of lipid metabolism due to genetic deficiency in microsomal triglyceride transfer protein (MTP). It is associated with defects in MTP-mediated lipid transfer onto apolipoprotein B (APOB) and impaired secretion of APOB-containing lipoproteins. Recently, MTP was shown to regulate the CD1 family of lipid antigen-presenting molecules, but little is known about immune function in ABL patients. Here, we have shown that ABL is characterized by immune defects affecting presentation of self and microbial lipid antigens by group 1 (CD1a, CD1b, CD1c) and group 2 (CD1d) CD1 molecules. In dendritic cells isolated from ABL patients, MTP deficiency was associated with increased proteasomal degradation of group 1 CD1 molecules. Although CD1d escaped degradation, it was unable to load antigens and exhibited functional defects similar to those affecting the group 1 CD1 molecules. The reduction in CD1 function resulted in impaired activation of CD1-restricted T and invariant natural killer T (iNKT) cells and reduced numbers and phenotypic alterations of iNKT cells consistent with central and peripheral CD1 defects in vivo. These data highlight MTP as a unique regulator of human metabolic and immune pathways and reveal that ABL is not only a disorder of lipid metabolism but also an immune disease involving CD1.
Zeissig
Sebastian
S
Division of Gastroenterology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Dougan
Stephanie K
SK
Barral
Duarte C
DC
Junker
Yvonne
Y
Chen
Zhangguo
Z
Kaser
Arthur
A
Ho
Madelyn
M
Mandel
Hannah
H
McIntyre
Adam
A
Kennedy
Susan M
SM
Painter
Gavin F
GF
Veerapen
Natacha
N
Besra
Gurdyal S
GS
Cerundolo
Vincenzo
V
Yue
Simon
S
Beladi
Sarah
S
Behar
Samuel M
SM
Chen
Xiuxu
X
Gumperz
Jenny E
JE
Breckpot
Karine
K
Raper
Anna
A
Baer
Amanda
A
Exley
Mark A
MA
Hegele
Robert A
RA
Cuchel
Marina
M
Rader
Daniel J
DJ
Davidson
Nicholas O
NO
Blumberg
Richard S
RS
D000012:Abetalipoproteinemia / Q000276:immunology*; D000328:Adult; D017951:Antigen Presentation; D018949:Antigens, CD1 / Q000502:physiology*; D055610:Antigens, CD1d / Q000502:physiology; D002352:Carrier Proteins / Q000502:physiology*; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D018664:Interleukin-12 / Q000502:physiology; D008297:Male; D008875:Middle Aged; D055611:Natural Killer T-Cells / Q000276:immunology; D055815:Young Adult
D018949:Antigens, CD1; D055610:Antigens, CD1d; C526877:CD1D protein, human; D002352:Carrier Proteins; C106092:microsomal triglyceride transfer protein; D018664:Interleukin-12