T-cell surface glycoprotein CD1e, soluble is required for the presentation of glycolipid antigens on the cell surface. The membrane-associated form is not active.
Complexes between CD1 molecules and self or microbial glycolipids represent important immunogenic ligands for specific subsets of T cells. However, the function of one of the CD1 family members, CD1e, has yet to be determined. Here, we show that the mycobacterial antigens hexamannosylated phosphatidyl-myo-inositols (PIM6) stimulate CD1b-restricted T cells only after partial digestion of the oligomannose moiety by lysosomal alpha-mannosidase and that soluble CD1e is required for this processing. Furthermore, recombinant CD1e was able to bind glycolipids and assist in the digestion of PIM6. We propose that, through this form of glycolipid editing, CD1e helps expand the repertoire of glycolipidic T cell antigens to optimize antimicrobial immune responses.
Dendritic cells express several alternatively spliced CD1e mRNAs. These molecules encode proteins characterized by the presence of either one, two, or three alpha domains and either a 51- or 63-amino acid cytoplasmic domain. Moreover, mRNAs encoding isoforms lacking the transmembrane domain are observed. Several of these CD1e isoforms were expressed in transfected cells, and two of them, with three alpha domains, displayed a particular processing pathway. These latter isoforms slowly leave the endoplasmic reticulum due to the presence of atypical dilysine motifs in the cytoplasmic tail. These molecules are associated with the beta(2)-microglobulin and accumulate in late Golgi and late endosomal compartments. In the latter compartments, they are cleaved into soluble forms that appear to be stable. In dendritic cells, these isoforms are mainly located in the Golgi apparatus, and upon maturation they are redistributed to late endosomal compartments. This work demonstrates the existence of CD1e molecules. As compared with other CD1 molecules, CD1e displays fundamentally different properties and therefore may represent a third type of CD1 molecules.
Herein, we report the DNA sequence of two human CD1 genes, R2 and R3, distinct from those encoding the CD1a, -b and -c antigens. Both genes appear to have an exon/intron structure analogous to the previously analyzed CD1 genes and to be functional on the basis of their sequence. Analysis of the variability patterns, potential intramolecular interactions and predicted secondary structure profile on an alignment of all known CD1 alpha chains suggest some shared structural features with major histocompatibility complex class I molecules in the alpha 1 domains but substantial differences in the alpha 2 domains. Sequence comparison shows that, while R2 is most related to CD1a, -b and -c, albeit to a somewhat lower degree than the latter are to themselves, R3 is more homologous to mouse than to human CD1, suggesting the existence of two functional classes within the CD1 gene family. We propose to retain the non-committal R2 and R3 names until the putative antigens have been identified and their tissue distribution has been established.
Protein involved in adaptive immunity. Vertebrates can develop a broad and almost infinite repertoire of antigen-specific receptors, which allows vertebrates to recognize almost any potential pathogen or toxin and to mount antigen-specific responses to it. Two types of adaptive immunity systems have evolved in vertebrates in order to generate immune receptor diversity. The jawed vertebrates strategy uses the V(D)JC recombination to achieve combinatorial diversity of immunoglobulin-based B cell receptors and T cell receptors. The jawless vertebrate strategy uses the somatic rearrangements of variable leucine-rich cassettes in the variable lymphocyte receptors (VLRs). The hallmarks of an adaptive immune system is the production of antigen-specific recognition receptor by somatic gene rearrangement. The long life of some antigen-primed cytotoxic lymphocytes and plasma cells provide protective memory to prevent reinvasion.
Protein involved in immunity, any immune system process that functions in the response of an organism to a potential internal or invasive threat. The vertebrate immune system is formed by the innate immune system (composed of phagocytes, complement, antimicrobial peptides, etc) and by the adaptive immune system which consists of T- and B- lymphocytes.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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