Strong, specific anti-human leukemia antisera prepared with the use of purified cell membrane antigen.

Two rabbits immunized with 15 micrograms of a purified human thymus leukemia-associated antigen preparation and boosted once with the same amount of the antigen preparation yielded antisera that showed strong specificity for human leukemic T-cells without any prior absorptions. These antisera from the two rabbits showed a 50% killing of cells at antiserum dilutions of 5700- and 1600-fold, respectively, against JM, a leukemic T-cell line, and slightly weaker activity against MOLT-4, another leukemia T-cell line. These antisera, without any absorption, showed no or minimal reaction against two nonmalignant B-cell lines (RPMI 1788 and RPMI 8057), a leukemic non-T, non-B-cell line (NALM-16), a leukemic pre-B-cell line (NALM-1), normal peripheral blood lymphocytes, and T-cells isolated from peripheral blood lymphocytes. Antiserum 7557, which showed the higher antibody activity, was further studied by an absorption test using various human cell lines. The antiserum showed strong activity against all three leukemic T-cell lines tested, i.e., CCRF-CEM, RPMI 8402, and CCRF-HSB-2, whereas it showed no significant activity against other cell lines which included two leukemic non-T, non-B-cell lines (KM-3 and NALM-6), NALM-1 and RPMI 1788. These are the first anti-human leukemia antisera, except for monoclonal hybridoma antibodies, that showed good specificity for leukemia cells without prior absorption. The present procedure of immunizing animals with a small amount of human thymus leukemia-associated antigen preparation isolated from cell membrane will also be useful for obtaining strong, specific antisera of other cell membrane antigens.