OKT4 epitope deficiency in significant proportions of the black population. A cause for underestimation of helper/suppressor lymphocyte ratios.

Monoclonal antibodies such as OKT4, OKT4A, Coulter T4, and Leu 3a are commonly used to define subsets of human peripheral blood lymphocytes having helper activity in vitro. Analysis of peripheral blood lymphocyte populations is a useful aid in the diagnosis of immunodeficiency syndromes. Peripheral blood lymphocytes of certain black and oriental patients do not mark with the conventional OKT4 antibody but do mark with OKT4A and Leu 3a antibodies. We determined helper subset populations of peripheral blood lymphocytes as delineated by OKT4, OKT4A, and Coulter T4 antibodies in 103 unselected patients from two tertiary care hospitals. Twenty percent of black patients without clinical immunodeficiency demonstrated marked reduced numbers of cells marking with OKT4 antibody, but normal numbers of cells marking with OKT4A and Coulter T4 antibodies. No white patients demonstrated this trait to the degree seen in black patients. Use of OKT4 antibody to define helper cell percentages in black patients may lead to underestimation of these percentages in certain hospital populations.