FLOW-CYTOMETRY ANALYSIS OF OKT4 EPITOPE DEFICIENCY IN SOUTH-AFRICAN BLACK-CHILDREN

A case of OKT4 epitope deficiency referred for investigation with susp ected immunodeficiency is described. Flow cytometry analysis of OKT4 e pitope deficiency in a study group of healthy black children showed di fferent manifestations of the lack of OKT4 epitope; a complete lack of OKT4(+)CD4(+) peripheral blood lymphocytes (PBL) with normal numbers of OKT4A(+) and Leu3a(+)CD4(+) PBL, decreased percentage OKT4(+)CD4(+) compared with OKT4A(+) and Leu-3a(+)CD4(+) PBL, decreased fluorescent staining intensity with OKT4 and a biphasic OKT4 staining pattern ass ociated with a reduced OKT4/Leu-3a ratio. The percentage and fluoresce nt intensity of OKT4(+)CD4(+) PBL in the study group were significantl y lower(P < 0.0001) than Leu-3a(+)CD4(+) and OKT4A(+)CD4(+) PBL. There is thus considerable risk of under-estimating the number of CD4(+) ce lls in black South Africans if the OKT4 MoAb is used.