Comparative analysis of human and macaque monkey CD4: differences in formaldehyde lability and conformation.
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.
Akari
H
H
Tsukuba Primate Center for Medical Science, National Institute of Infectious Diseases, Ibaraki, Japan.
Terao
K
K
Nam
K H
KH
Adachi
A
A
Yoshikawa
Y
Y
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
D015704:CD4 Antigens; D005404:Fixatives; D005557:Formaldehyde