Based on the earlier observation that DNP-HSA interacts directly with C1q, a subcomponent of the first component of complement (Loos and König, 1977), evidence is presented that TNP bound to erythrocytes (E-TNP) can interact with the whole complement sequence leading to the lysis of the TNP-carrying erythrocytes: in this test system the erythrocytes are used as an indicator of the TNP-complement reaction. To exclude any antibody-mediated lysis either the heterologous sera were exhaustively absorbed with the erythrocytes used in the test system or serum and erythrocytes of one individual person were taken. The strongly temperature-dependent interaction of TNP-sulfonic acid with the erythrocytes resulted in the formation of E-TNP as well as of a TNP-protein complex released into the supernatant. The TNP-protein complex strongly inhibited purified C1 similar to DNP-HSA. The antibody independent lysis of E-TNP by complement was dependent upon the TNP concentration per cell, the temperature and time as well as the complement concentration. The reaction of E-TNP with complement showed similar characteristics to those for the reaction of antibody sensitized erythrocytes (EA) with complement. E-TNP is a helpful tool to study antibody-independent activation of the complement system. © 1978.
