Lymphocyte-dependent antibodies (LDA's) directed against antigenic determinants present on lymphoblastoid cell lines as well as human leukemia blast cells were demonstrated in heterologous antisera obtained by immunizing rabbits with a membrane fraction from RPM1-4265 (a lymphoblastoid cell line derived from a patient with chronic myelogenous leukemia).

LDA was present at high titers against B-lymphoblastoid, myelomonocytic, and stem cell lines. The T-lymphoblastoid cell line MOLT-4, however, did not react. LDA was demonstrated against acute myelogenous as well as lymphoblastic leukemia cells. The reactivity was not directed against phytohemagglutinin-induced blastoid antigens, fetal antigens, or fetal calf serum. Absorptions with lymphoblastoid cell lines removed all LDA reactivity. Similar results were obtained by absorbing the rabbit antiserum with acute lymphoblastic and/or acute myelogeneous leukemia cells.

These findings indicate the presence of cross-reactive antigens between lymphoblastoid cell lines and leukemia cells. Furthermore, cross-reactivity between acute lymphoblastic and acute myelogenous leukemia cells was demonstrated.

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This work was supported by grants CA 12800 and CA 16880 from the National Cancer Institute.

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