Density gradient separation of marrow precursor cells restricted for antibody specificity.

Potentially immunocompetent cells of (C57BL/6 x DBA/2) F(1) mouse bone marrow are committed to antigenic determinants of sheep or burro erythrocytes prior to interaction with thymus-derived cells and participation in immune responses to administered antigens. At this stage of differentiation marrow cells of this particular mouse strain are not yet restricted for the immunoglobulin M or immunoglobulin G antibody class. By equilibrium centrifugation in discontinuous gradients of bovine serum albumin, precursors of cells that produce antibody to sheep erythrocytes migrate to denser regions, whereas the precursors of immunocytes that produce antibody to burro erythrocytes remain in the lower density regions. cursors for all specificities.