B-LYMPHOID TO GRANULOCYTIC SWITCH DURING HEMATOPOIESIS IN A TRANSGENIC MOUSE STRAIN

B-lymphoid and myeloid development are markedly perturbed in a unique transgenic mouse strain, max 41. Pro-B, pre-B, and B lymphocytes were severely reduced but granulocytes were greatly elevated. This phenotyp e could be adoptively transferred with bone marrow cells. It was not a lleviated by bcl-2 or myc transgenes that promote lymphocyte survival or proliferation. Bitransgenic myc/max 41 mice developed pre-B cell ly mphoma. An accompanying massive granulocytosis unexpectedly proved to be clonally derived from the pre-B lymphoma cells. These observations suggest that B lymphopoiesis in max 41 mice has been diverted to granu locyte production. Since neither cell type expressed the transgene, th is novel lymphomyeloid deviation probably reflects insertional alterat ion of a hematopoietic regulatory gene.