CUTTING EDGE
IMMUNOLOGY
THE
OF
JOURNAL
Cutting Edge: A Naturally Occurring Mutation in CD1e
Impairs Lipid Antigen Presentation
1
Sylvie Tourne,
2
*
‡§
Blandine Maitre,*
†‡§
Anthony Collmann,
¶
Emilie Layre,
Sabrina Mariotti,
¶
Franc ¸ois Signorino-Gelo,*
‡§
Caroline Loch,
#
Jean Salamero,**
††
Martine Gilleron,
Catherine Ange ´nieux,*
‡§
Jean-Pierre Cazenave,
†‡§
Lucia Mori,
¶
Daniel Hanau,*
‡§
Germain Puzo,
Gennaro De Libero,
¶
and Henri de la Salle
2
*
‡§
The human CD1a– d proteins are plasma membrane
molecules involved in the presentation of lipid Ags to T
cells. In contrast, CD1e is an intracellular protein present
in a soluble form in late endosomes or lysosomes and is
essential for the processing of complex glycolipid Ags such
as hexamannosylated phosphatidyl-myo-inositol, PIM
6
.
CD1e is formed by the association of
2
-microglobulin
with an -chain encoded by a polymorphic gene. We re-
port here that one variant of CD1e with a proline at po-
sition 194, encoded by allele 4, does not assist PIM
6
presentation to CD1b-restricted specific T cells. The
immunological incompetence of this CD1e variant is
mainly due to inefficient assembly and poor transport
of this molecule to late endosomal compartments. Al-
though the allele 4 of CD1E is not frequent in the pop-
ulation, our findings suggest that homozygous individ-
uals might display an altered immune response to
complex glycolipid Ags. The Journal of Immunology,
2008, 180: 3642–3646.
I
n humans, CD1a– d present lipids to T cells (1). They ac-
quire self-lipid ligands in the endoplasmic reticulum
(ER),
3
where they are assembled, and lipid Ags in the en-
dosomal compartments, where they cycle through after a transit
from the cell surface (2). CD1e also participates in the presen-
tation of lipids to T cells, but not as an Ag-presenting molecule.
CD1e never transits through the plasma membrane but is di-
rectly targeted from Golgi compartments to early endosomes
before reaching late endosomes and lysosomes (3). In these lat-
ter compartments CD1e facilitates the processing of complex
glycolipids, which is required for their presentation by CD1b
molecules. In particular, CD1e is essential in the processing of
hexamannosylated phosphatidyl-myo-inositol (PIM
6
) by the ly-
sosomal -mannosidase (4).
CD1, like MHC class I molecules, is composed of a trans-
membrane -chain that noncovalently associates with the
2
-
microglobulin (
2
m). The -chain folds in three structural
domains (1–3), with the 1 and 2 domains delimiting a hy-
drophobic pocket-containing groove in which lipid ligands
bind. For CD1e, the -chain is cleaved between the 3 and the
transmembrane domains in late endosomal compartments,
generating by this way soluble CD1e, which represents the
CD1e active form (4, 5). The human CD1 genes are poorly
polymorphic. Only two alleles have been described for CD1A,
B, C, and D (6, 7), the polymorphism of CD1B and C being
silent (6, 7). CD1E is the most polymorphic CD1 gene, six al-
leles having been reported (6, 8, 9). Among individuals from
diverse ethnic backgrounds, alleles 1 and 2 display a frequency
of 49 and 51%, respectively (6), whereas the four other alleles
have been described once (8, 9). The polymorphic nucleotides
are located in exons 2 or 3 of the CD1E gene, encoding the 1
and 2 domains, respectively (see Fig. 1) (6, 8, 9).
The impact of the polymorphism of the CD1 gene on the
structure and function of the encoded protein has been poorly
addressed. The products of CD1A alleles are similarly expressed
on the cell surface and display similar structural characteristics
(10), whereas no significant correlation between the CD1 ge-
notype and susceptibility to Mycobacterium malmoense pulmo-
nary disease (11) or chronic dysimmune neuropathies (12)
could be inferred.
*Unite ´ 725 “Biology of Human Dendritic Cells” and
†
Unite ´ 311, Institut National de la
Sante ´ et de la Recherche Me ´dicale (INSERM), Strasbourg, France;
‡
Etablissement Fran-
c ¸ais du Sang-Alsace, Strasbourg, France;
§
Universite ´ Louis-Pasteur, Strasbourg, France;
¶
Experimental Immunology, Department of Research, Basel University Hospital, Basel,
Switzerland;
Institut de Pharmacologie et de Biologie Structurale, Centre National de la
Recherche Scientifique (CNRS) Unite ´ Mixte de Recherche (UMR) 5089, Department of
Molecular Mechanisms of Mycobacterial Infections, Toulouse, France;
#
Institut de Ge ´ne ´-
tique et de Biologie Mole ´culaire et Cellulaire, CNRS/INSERM, Universite ´ Louis-Pasteur,
Illkirch-Graffenstaden, France; and **Imaging Center and
††“
Molecular Mechanisms of
Intracellular Transport,” UMR144 CNRS, Institut Curie, Paris, France
Received for publication November 5, 2007. Accepted for publication January 25, 2008.
The costs of publication of this article were defrayed in part by the payment of page charges.
This article must therefore be hereby marked advertisement in accordance with 18 U.S.C.
Section 1734 solely to indicate this fact.
1
This work was supported by Institut National de la Sante ´ et de la Recherche Me ´dicale,
Etablissement Franc ¸ais du Sang-Alsace and Agence Nationale de Recherche Microbiolo-
gie-Maladie Emergentes (ANR-05-MIME-006), the European Union funded TB-VAC
tuberculosis vaccine project (LSHP-CT-2003-503367), Swiss National Fund Grant
3100A0-109918, and the Basel Cancer League (Krebsliga Beider Basel). B.M. was the re-
cipient of a grant from Association de Recherche et de De ´veloppement en Me ´decine et en
Sante ´ Publique (ARMESA).
2
Address correspondence and reprint requests to Dr. Sylvie Tourne or Dr. Henri de la
Salle, Institut National de la Sante ´ et de la Recherche Me ´dicale, Unite ´ 725, Etablissement
Franc ¸ais du Sang-Alsace, 10 Rue Spielmann, 67065 Strasbourg Cedex, France. E-mail
addresses: sylvie.tourne@efs-alsace.fr and henri.delasalle@efs-alsace.fr
3
Abbreviations used in this paper: ER, endoplasmic reticulum;
2
m,
2
-microglobulin;
Endo-H, endoglycosidase H; GM1, monosialoganglioside GM1; MFI, median fluores-
cence intensity; PIM, phosphatidyl-myo-inositol-mannoside; PIM
6
, hexamannosylated
phosphatidyl-myo-inositol; PNGase F, peptide N-glycosidase F; rs, recombinant soluble
(prefix); WB, Western blotting.
Copyright © 2008 by The American Association of Immunologists, Inc. 0022-1767/08/$2.00
www.jimmunol.org