Dendritic cell derived exosomes express a Streptococcus pneumoniae capsular polysaccharide type 14 cross-reactive antigen that induces protective immunoglobulin responses against pneumococcal infection in mice (43.10)

• Published in: The Journal of immunology (1950) Vol. 178; no. 1_Supplement; p. S38
• Main Authors: Colino, Jesus, Snapper, Clifford
• Format: Journal Article
• Language: English
• Published: 01.04.2007
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.178.Supp.43.10

Abstract Exosomes activate T cells in vivo, but whether exosomes are able to induce humoral immune responses is still unknown. We found that dendritic cells, but not other immune cells, constitutively release an exosome-associated glycoconjugate that is cross-reactive with the capsular polysaccharide of Streptococcus pneumoniae type 14 (Cps14-CRA). Cps14-CRA was localized to the cholesterol-enriched microdomains or rafts of the exosomes and was mapped to the β 1→6 branched N-acetyl-lactosamine derivatives of the Cps14-CRA. Injection of CFA primed naïve mice with purified DC exosomes induced Ig anti-Cps14 responses composed predominantly of IgM, IgG3 and IgG1. These responses were associated with protection against a lethal challenge with live S. pneumoniae type 14, but not with type 3 bacteria, and was correlated with the titer of elicited IgM and IgG3 anti-Cps14. These data show for the first time, that exosomes can induce a humoral immune response to an associated unprocessed, autologous antigen. Although anti-Cps14 Ig responses are specifically demonstrated, these could reflect a broader mechanism that modulates both natural immunity and autoimmunity to other glycotopes.