Demonstration and characterization of virus released by murine B cell leukemia cells (BCL1)

LPS-stimulated leukemia cells derived from BALB/c mice bearing transplantable B-lymphocytic leukemia (BCL1) which arose spontaneously in a female BALB/c mouse, contained viral particles as suggested by electron microscopy as well as by tissue cultures using the XC assay. Some cell free extracts prepared from BCL1 cells were capable of transforming normal B-lymphocytes when inoculated into untreated syngeneic recipients. Cytogenetic analysis of spleen cells obtained from a splenomegalic male mouse neonatally inoculated with cell-free extract indicated that the tumor cells had a male karyotype with 42 chromosomes as compared to 37 chromosomes and a female karyotype in original BCL1 cells, thus excluding the possibility of tumor propagation by transplantation of intact BCL1 cells. These findings suggest viral involvement in the etiology of BCL1.