Split unresponsiveness to the trinitrophenyl determinant. I. Manoeuvers which suppress either humoral or cell-mediated immune responses.

2,4,6-Trinitrobenzene sulfonic acid (TNBS) injected intravenously (i.v.) makes mice fully tolerant to the trinitrophenyl (TNP) determinant. Administration of in vitro TNP-labeled syngeneic erythrocytes or thymocytes renders mice unable to develop contact sensitivity to picryl chloride, while the humoral anti-TNP responses seem to be unaffected. The reverse was found after pretreatment of mice with TNP-labeled isologous IgG (MGG) since only anti-TNP antibody responses, but not contact sensitivity to picryl chloride, were significantly reduced. TNP-coupled macrophages given to animals suppressed both the cell-mediated and humoral responses, and this might be due to the presence on their surface of TNP-labeled cytophilic antibody. TNBS administered i.v. binds to circulating proteins and formed blood elements. Thus the split unresponsiveness affecting either humoral or cell-mediated compartments after the injection of TNP-MGG or of haptenated cells respectively, is presumably due to dissecting events which in vivo after the injection of TNBS, occur simultaneously. These results may be interpreted to indicate that split unresponsive states to TNP determinants are mediated two independent mechanisms which require different tolerogen presentations to be triggered.