Induction of exosome release in primary B cells stimulated via CD40 and the IL-4 receptor.
Exosomes are lipid-bound nanovesicles formed by inward budding of the endosomal membrane and released following fusion of the endosomal limiting membrane with the plasma membrane. We show here that primary leukocytes do not release exosomes unless subjected to potent activation signals, such as cytokine or mitogen stimulation. In particular, high levels of exosomes were released when murine splenic B cells were stimulated via CD40 and the IL-4 receptor. This property was shared by B cells from different anatomic locations, as newly formed marginal zone and follicular B cells were capable of secreting exosomes upon CD40/IL-4 triggering. B cell exosomes expressed high levels of MHC class I, MHC class II, and CD45RA (B220), as well as components of the BCR complex, namely, surface Ig, CD19, and the tetraspanins CD9 and CD81. Ig on the plasma membrane of primary B cells was targeted to the exosome pathway, demonstrating a link between the BCR and this exocytic pathway. IgD and IgM were the predominant Ig isotypes associated with CD40/IL-4 elicited exosomes, though other isotypes (IgA, IgG1, IgG2a/2b, and IgG3) were also detected. Together, these results suggest that exosome release is not constitutive activity of B cells, but may be induced following cell: cell signaling.
Department of Microbiology and Immunology, Christchurch School of Medicine, University of Otago, Dunedin, New Zealand.
Sarah C
SC
Saunderson
Petra C
PC
Schuberth
Amy C
AC
Dunn
Lilija
L
Miller
Barry D
BD
Hock
Philippa A
PA
MacKay
Norbert
N
Koch
Ralph W
RW
Jack
Alexander D
AD
McLellan
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism; D016175:B-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism*; D019013:CD40 Antigens / Q000502:physiology*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D022162:Cytoplasmic Vesicles / Q000276:immunology* / Q000378:metabolism*; D005089:Exocytosis / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D019948:Receptors, Interleukin-4 / Q000502:physiology*; D012995:Solubility; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000378:metabolism
D019013:CD40 Antigens; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; D019948:Receptors, Interleukin-4