title: Mutations in human CD4 impair the functional interaction with different human and mouse class II isotypes and alleles.
abstract: The structure-function of the CD4-class II MHC interaction was investigated. Two functional assays were used to assess the responses of the 3DT52.5.8 murine T cell hybridoma expressing human CD4 (h-CD4) or murine CD4 (m-CD4). First, we determined the responses of the CD4+ and CD4-effector cells toward DAP-3 cells co-expressing the cognate alloantigen H-2Dd together with several human (DRw52b, DR4-Dw4, DR2A, and DPw2) and murine (I-Ab, I-Ak, IA alpha b I-A beta k and I-Ek) class II alleles and isotypes. We found that h-CD4 and m-CD4 strongly enhance the T cell response to H-2Dd, demonstrating that interspecies CD4/class II interactions occur efficiently. Furthermore, mutations in h-CD4 at positions 19, 89, and 165 markedly reduced the interaction with both human class II and mouse class II, indicating that the structural features of this cross-species interaction are strongly conserved. This was further supported by the finding that a h-CD4 deletion mutant (deletion F43-S49) interacted with both human and murine class II. Moreover, as 3DT cells express the responsive V beta element for the bacterial superantigen staphylococcal enterotoxin B, a co-receptor assay was conducted. DAP-3 cells expressing only class II molecules were used as APCs to present staphylococcal enterotoxin B to h-CD4+ and m-CD4+ T cells. h-CD4 and m-CD4 were able to enhance the T cell response to staphylococcal enterotoxin B, further demonstrating the conservation of the CD4-class II MHC interaction.
authors.affiliation: Immunology Laboratory, Montreal Clinical Research Institute, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Fleury
authors.forename: B
authors.initials: B
authors.lastname: Huang
authors.forename: A
authors.initials: A
authors.lastname: Zerbib
authors.forename: G
authors.initials: G
authors.lastname: Croteau
authors.forename: E O
authors.initials: EO
authors.lastname: Long
authors.forename: R P
authors.initials: RP
authors.lastname: Sekaly
mesh_terms: D000483:Alleles; D000818:Animals; D015704:CD4 Antigens / Q000235:genetics* / Q000378:metabolism*; D004768:Enterotoxins / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D009154:Mutation / Q000276:immunology*; D013045:Species Specificity; D013211:Staphylococcus aureus / Q000276:immunology; D013329:Structure-Activity Relationship; D018089:Superantigens / Q000276:immunology
chemical_list: D015704:CD4 Antigens; D004768:Enterotoxins; D000949:Histocompatibility Antigens Class II; D018089:Superantigens; C031818:enterotoxin B, staphylococcal