The use of a monoclonal i-j-specific antibody to distinguish cells in the feedback suppression circuit from those in the contrasuppressor circuit.

A monoclonal anti-I-Jb serum designated D-7 reacts in high titer with three different T-cell subsets and one cell-free product involved in generating contrasuppressive activity, but has no activity against I-J T-cell subsets (or their cell-free mediators) involved in feedback suppression. These results give evidence for heterogeneity in the I-J subregion. They also indicate that the serological markers on I-J+ cells may define the functional activity of the regulatory circuits they belong to. Clearly, they do not separate the role that the cells play within a particular immunoregulatory circuit, i.e., inducer, transducer, or effector cells.