Evidence for origin of certain childhood acute lymphoblastic leukemias and lymphomas in thymus-derived lymphocytes

Lymphoblasts from children with acute lymphoblastic leukemia (ALL) or malignant lymphoblastic lymphoma were studied using surface markers characteristic of T and B lymphocytes. A B-cell marker, i.e. surface immunoglobulin, was absent in all cases studied. Fouteen of 22 children (64%) had lymphoblasts with one or both markers of T lymphocytes, i.e. receptors for sheep erythrocytes (E) and/or human T-lymphocyte antigen (HTLA) detectable using heterologous antithymocyte sera absorbed with B lymphocytes. In all instances, lymphoblasts which carried E receptors also carried HTLA. However, lymphoblasts in 6 cases carried HTLA but not E receptors. It is possible that ALL may often involve T lymphocytes which are early in differentiation (i.e. prior to development of E receptors) or, alternatively, that E receptors may be lost from T cells following malignant transformation. Thymus enlargement was found only in cases of ALL or lymphoma where T markers were present. Lymphoblasts carried the same markers when examined in various sites and at various times from the same patient.