Antigenic cross-reactivity between human leukemic cells and dinitrophenylated normal leukocytes.

Dinitrofluorobenzene-modified normal human leukocytes (DNP-LK) have been shown to evoke the production of antibodies, which following absorption with erythrocytes and unmodified leukocytes (UN-LK) had residual leukoagglutinating activity against human leukemic cells (HLC). In the present study we observed that rabbit antisera prepared against cell membrane extracts of DNP-modified granulocytes (DNP-GM) or lymphocytes (DNP-LM) were cytotoxic to HLC. By passive hemagglutination, these antisera were specifically reactive with DNP-GM or DNP-LM conjugated to sheep erythrocytes (SRBC) but not with DNP-modified bovine serum albumin (DNP-BSA) or bovine gamma globulin (DNP-BGG) nor with UN-LK, suggesting that the antisera were devoid of anti-DNP antibodies. Rabbit anti-DNP-BSA or anti-DNP-BGG failed to react with DNP-LK, and anti-DNP antibodies in these sera could not be absorbed by DNP-LK, suggesting that DNP groups either were not expressed on the surface of DNP-LK or were not detectable by these methods. These data, together with our recent finding that dinitrophenylation alters the expression of histocompatibility antigens, suggest that neoantigens cross-reactive with HLC antigens are induced by DNP modification of membrane antigens of normal leukocytes, and that the antibodies produced against these DNP-modified cells are directed mainly against the modified protein and not against the DNP moiety per se.