Measurement of lymphocyte activation by a chromatin topo-optical reaction. Mechanism and specificity of the test.

A rapid inexpensive method is presented for detecting peripheral blood lymphocyte chromatin activation by the neutral red "topo-optical" reaction, which causes strong and easily measurable birefringence in the lymphocyte nuclei. This reaction can be enhanced by fixing the cells with 150 mM/l NaCl in 70% ethanol and/or by treating the unfixed cellular suspensions with 0.2 M/l HCl to remove histones. In histone-removed preparations, 30 min DNase I treatment almost completely abolished the birefringent reaction, whereas RNase treatment resulted in only 18% loss. Chromatin activation induced by enzyme inhibition increased chromatin birefringence significantly. The same phenomenon could be induced in sensitive subjects' lymphocytes by specific antigens or haptens much more rapidly. The monocytes were not activated to a significant extent. In non-sensitive subjects different kinetics of antigen or hapten-dependent activation and no cytotoxic effects have been observed. Depletion of T-lymphocytes in vivo in SLE patients or by in vitro treatment with 0.5 mM/l KCN as well as with 0.02% trypsin has caused a significant drop in the mean chromatin birefringence. The effect of trypsin was reversible.