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The BCR/ABL fusion gene is pathognomonic for the human disease chronic myeloid leukaemia (CML). CML is a malignant myeloproliferative disorder that is characterised at the cytogenetic level by the Philadelphia (Ph) translocation between chromosomes 9 and 22. At the molecular level this results in the juxtaposition of parts of the BCR and ABL genes to form a fusion gene (that is, BCR/ABL). The p210 protein tyrosine kinase product of BCR/ABL is presumed to be responsible for the biological and clinical features of CML in humans. A vast amount of work has been done on the molecular biology and biochemistry of p210 (reviewed in ) but this article is concerned with the cell biological consequences of p210 expression.

Twenty-nine patients previously diagnosed as having suffered from farmer's lung in or before 1970 were asked whether the condition had recurred and what measures they had taken to avoid such recurrence. Those who had retired from farming had been least affected by recurrence, while those who continued to farm had been protected by making silage instead of hay or by wearing protective respirators. To be effective, a respirator should be worn on every occasion that farm dust is encountered and must be properly maintained.

An in vivo culture system, the agar diffusion chamber technique, has been used to measure the population of colony-forming precursor cells in the bone marrow of patients receiving immunotherapy during acute myeloid leukaemia in remission. The results of these assays indicate that (1) the level of committed granulocytic stem cells usually remains below the range found in normal marrow throughout remission, and (2) the maintenance of adequate cell counts in the blood may be due to increased cell production by these early granulocytic precursor cells. The relevance of these findings to the possible protective effect of immunotherapy against cytotoxic chemotherapy is discussed.