Novel MHC class I structures on exosomes.
Exosomes are nanometer-sized vesicles released by a number of cell types including those of the immune system, and often contain numerous immune recognition molecules including MHC molecules. We demonstrate in this study that exosomes can display a significant proportion of their MHC class I (MHC I) content in the form of disulfide-linked MHC I dimers. These MHC I dimers can be detected after release from various cell lines, human monocyte-derived dendritic cells, and can also be found in human plasma. Exosome-associated dimers exhibit novel characteristics which include 1) being composed of folded MHC I, as detected by conformational-dependent Abs, and 2) dimers forming between two different MHC I alleles. We show that dimer formation is mediated through cysteine residues located in the cytoplasmic tail domains of many MHC I molecules, and is associated with a low level of glutathione in exosomes when compared with whole cell lysates. We propose these exosomal MHC I dimers as novel structures for recognition by immune receptors.
Lynch
Sarah
S
Bute Medical School, University of St Andrews, Fife, United Kingdom.
Santos
Susana G
SG
Campbell
Elaine C
EC
Nimmo
Ailish M S
AM
Botting
Catherine
C
Prescott
Alan
A
Antoniou
Antony N
AN
Powis
Simon J
SJ
D000483:Alleles; D003545:Cysteine; D004220:Disulfides; D055354:Exosomes / Q000737:chemistry*; D005978:Glutathione / Q000032:analysis; D015395:Histocompatibility Antigens Class I / Q000737:chemistry*; D006801:Humans; D011487:Protein Conformation; D055503:Protein Multimerization
D004220:Disulfides; D015395:Histocompatibility Antigens Class I; D005978:Glutathione; D003545:Cysteine