title: Comparative analysis of human and macaque monkey CD4: differences in formaldehyde lability and conformation.
abstract: Here we characterized macaque monkey CD4 by flow cytometry. The results showed that relatively lower fluorescence intensity was observed depending on the monoclonal antibodies (mAbs) used for staining; Leu-3a exhibited four-fold lower intensity than Nu-Th/i, and that formaldehyde fixation dramatically reduced fluorescence intensity of macaque CD4+ cells stained with Leu-3a but not of human cells. Nu-Th/i is therefore preferable for the analysis of macaque CD4. Pretreatment of either mAb inhibited the other mAb binding to human CD4. On the contrary, Nu-Th/i inhibited Leu-3a binding but Leu-3a poorly blocked Nu-Th/i binding to the macaque CD4. These results indicate that Leu-3a and Nu-Th/i epitopes are conserved in macaque CD4 but Leu-3a epitope is conformationally cryptic and/or fragile, resulting in the lower affinity. Amino acid sequence alignment of CD4 domain 1 shows that the substitutions outside the linear Leu-3a epitope may determine these characteristics of macaque CD4.
authors.affiliation: Tsukuba Primate Center for Medical Science, National Institute of Infectious Diseases, Ibaraki, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Akari
authors.forename: K
authors.initials: K
authors.lastname: Terao
authors.forename: K H
authors.initials: KH
authors.lastname: Nam
authors.forename: A
authors.initials: A
authors.lastname: Adachi
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshikawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015704:CD4 Antigens / Q000737:chemistry* / Q000187:drug effects; D005260:Female; D005404:Fixatives / Q000494:pharmacology*; D005434:Flow Cytometry; D005557:Formaldehyde / Q000494:pharmacology*; D006801:Humans; D008252:Macaca fascicularis; D008253:Macaca mulatta; D008297:Male; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D015704:CD4 Antigens; D005404:Fixatives; D005557:Formaldehyde