Heterogeneity in expression of the T4 epitope in black individuals.

The T-cell differentiation antigen T4/Leu3 has been described as a non-polymorphic molecule important in T-cell recognition of class II major histocompatibility complex antigens. We report the polymorphism of this molecule in black individuals as manifest by a heterogeneity of staining with OKT4 monoclonal antibody. No such heterogeneity was observed when staining with other monoclonal antibodies that bind to different epitopes of the same molecule. No heterogeneity of staining with any of the monoclonal antibodies was observed in whites. Three patterns of OKT4 staining emerged: intact, deficient, and intermediate. This heterogeneity is likely to be due to an intrinsic heterogeneity in T4 epitope expression and not secondary to an interfering plasma factor as shown by the preservation of the T4 epitope pattern after a 3-day culture in the presence or absence of mitogen. Family studies strongly suggest that this heterogeneity in T4 epitope expression is inherited in an autosomal codominant fashion.