Generation of anti-ssDNA antibodies by persistent immunization of mice with sheep erythrocytes.

Immunization of (DBA/2) mice with sheep erythrocytes (1 X 10(8) red cells, once weekly for 2 months) elicited anti-sheep erythrocyte antibodies, a part of which combined with ssDNA. By contrast, immunization with rat (Fisher) erythrocytes (1 X 10(8) red cells, once weekly for 2 weeks) did not elicit antibodies cross-reactive with ssDNA. The antibody response (IgM and IgG) to sheep erythrocytes rose sharply and subsequently tapered off (usually within the first 2 weeks). The level of IgG antibodies cross-reactive with ssDNA increased and, after ca. 1 month, decreased. No increase in anti-trinitrophenyl antibodies was detected. These results suggest the existence of a homeostatic mechanism. The anti-ssDNA antibodies bound to sheep erythrocytes, ssDNA and, marginally, to trinitrophenyl-gelatin; they did not bind to poly-D-glutamic acid, rat erythrocytes or mouse erythrocytes. Treatment of sheep red blood cells with neuraminidase, proteinase K, trypsin, or DNase did not alter the erythrocytes' capacity to bind the anti-ssDNA antibodies; solubilization of the erythrocytes with Triton X-100 abolished the binding. Neither a methanol:chloroform (1:1) extract (which contains the erythrocyte phospholipids) nor the residue (left after the extraction) bound anti-ssDNA antibodies. The determinant mediating the binding could be conformational.