Suppressor T cells induced in vivo by tolerogenic conjugates of a given antigen and monomethoxypolyethylene glycol downregulate antibody formation also to a second antigen, if the latter is presented as a covalent adduct with the former.

Recent results of studies employing tolerogenic monomethoxypolyethylene glycol (mPEG) conjugates of antigens are briefly reviewed. Administration of antigen (mPEG)n conjugates into mice induced antigen-specific suppressor T (Ts) cells, from which a suppressor factor (TsF) was extracted. These Ts cells were cloned and shown to be Thy1.2+, CD3+, CD4-, CD5-, CD8+ and to express the alpha beta heterodimer of conventional T cell receptors (TCR). The TsF of a clone of OVA-specific Ts cells shared the epitopes of the alpha and beta chains of TCR, whereas the TsF of T cells of an HIgG-specific clone shared only the epitope of the alpha chains of TCR; OVA and HIgG represent ovalbumin and human monoclonal (myeloma) IgG. These studies have provided evidence for the phenomenon of "linked immunological suppression" which may be summarized by the statement "Ts cells specific for an epitope of a given antigen, AgA, suppress the antibody response to an unrelated antigen, AgB, only if the latter is presented in the form of a covalent adduct, AgA-AgB, to the immune system of the animal pretolerized with AgA (mPEG)n, but not if AgB is presented as a mixture with AgA.