title: The tetraspanin CD9 mediates lateral association of MHC class II molecules on the dendritic cell surface.
abstract: We have found that MHC class II (MHC II) molecules exhibit a distinctive organization on the dendritic cell (DC) plasma membrane. Both in DC lysates and on the surface of living cells, I-A and I-E molecules engaged in lateral interactions not observed on other antigen-presenting cells such as B blasts. Because DCs and B blasts express MHC II at comparable surface densities, the interaction was not due to simple mass action. Instead, it reflected the selective expression of the tetraspanin CD9 at the DC surface. I-A and I-E molecules coprecipitated with each other and with CD9. The association of heterologous MHC II molecules was abrogated in DCs from CD9(-/-) mice. Conversely, expression of exogenous CD9 in B cells induced MHC II interactions. CD9 is thus necessary for the association of heterologous MHC II, a specialization that would facilitate the formation of MHC II multimers expected to enhance T cell receptor stimulation by DCs.
authors.affiliation: Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520-8002, USA.
authors.forename: Julia J
authors.initials: JJ
authors.lastname: Unternaehrer
authors.forename: Amy
authors.initials: A
authors.lastname: Chow
authors.forename: Marc
authors.initials: M
authors.lastname: Pypaert
authors.forename: Kayo
authors.initials: K
authors.lastname: Inaba
authors.forename: Ira
authors.initials: I
authors.lastname: Mellman
mesh_terms: D000818:Animals; D017951:Antigen Presentation; D015703:Antigens, CD / Q000737:chemistry / Q000502:physiology*; D001402:B-Lymphocytes / Q000276:immunology; D018122:B7-1 Antigen / Q000032:analysis; D051940:B7-2 Antigen / Q000032:analysis; D003713:Dendritic Cells / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000032:analysis / Q000737:chemistry*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D060245:Tetraspanin 29
chemical_list: D015703:Antigens, CD; D018122:B7-1 Antigen; D051940:B7-2 Antigen; C554870:Cd9 protein, mouse; D000949:Histocompatibility Antigens Class II; C024138:I-E-antigen; D008562:Membrane Glycoproteins; D060245:Tetraspanin 29