COMPARATIVE-ANALYSIS OF HUMAN AND MACAQUE MONKEY CD4 - DIFFERENCES INFORMALDEHYDE LABILITY AND CONFORMATION

Here we characterized macaque monkey CD4 by flow cytometry. The result s showed that relatively lower fluorescence intensity was observed dep ending on the monoclonal antibodies (mAbs) used for staining; Leu-3a e xhibited four-fold lower intensity than Nu-Th/i, and that formaldehyde fixation dramatically reduced fluorescence intensity of macaque CD4cells stained with Leu-3a but not of human cells. Nu-Th/i is therefore preferable for the analysis of macaque CD4. Pretreatment of either mA b 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-Sa and Nu-Th/i epi topes are conserved in macaque CD4 but Leu-3a epitope is conformationa lly cryptic and/or fragile, resulting in the lower affinity. Amino aci d sequence alignment of CD4 domain 1 shows that the substitutions outs ide the linear Leu-3a epitope may determine these characteristics of m acaque CD4.