The Philadelphia (Ph) chromosome breakpoints in chronic myelocytic leukaemia are clustered on chromosome 22 band q11 in a 5.8-kilobase (kb) region designated bcr. The c-abl protooncogene is translocated from chromosome 9 band q34 into bcr and the biochemical consequence of this molecular rearrangement is the production of an abnormal fusion protein bcr-abl p210 with enhanced protein-tyrosine kinase activity compared to the normal p145 c-abl protein. The Ph chromosome translocation is also seen in some acute lymphoblastic leukaemias with B-cell precursor phenotypes some of which have bcr rearrangement (bcr+) and some do not (bcr-). We present evidence that the Ph+, bcr- leukaemias are associated with a novel p190 abl kinase. We propose that acute lymphoblastic leukaemias that are bcr+, p210+ are probably lymphoid blast crises following a clinically silent chronic phase of chronic myelocytic leukaemia arising in multipotential stem cells whereas bcr-, p190+ cases are de novo acute lymphoblastic leukaemias arising in more restricted precursors.

A 57-year-old female patient, admitted for an acute abdominal syndrome, was found to have an extensive proliferation of mast cells both in the peripheral blood and the bone marrow. Cytochemical studies confirmed the mast cell characteristics of the pathological cell population, while the immunophenotype strongly suggested a bone marrow origin of this malignancy. The course of the disease was not affected by antiproliferative treatment and the patient, after progressive general deterioration, died of intractable haemorrhage. On both clinical and haematological criteria it seems possible to distinguish this rare case of primary mast leukaemia from the more common form of tissue mastocytosis with secondary leukaemia.

A linkage between presence of Sickle Haemoglobin (HbS) and protection from malaria infection and clinical manifestations in certain areas was suspected from early observations and progressively elucidated by more recent studies. Research has confirmed the abovementioned connection, but also clarified how such protection may be abolished by coexistence of sickle cell trait (HbS trait) and alpha thalassemia, which may explain the relatively low incidence of HbS trait in the Mediterranean. The mechanisms of such protective effect are now being investigated: factors of genetic, molecular and immunological nature are prominent. As for genetic factors attention is given to the role of the red blood cell (RBC) membrane complement regulatory proteins as polymorphisms of these components seem to be associated with resistance to severe malaria; genetic ligands like the Duffy group blood antigen, necessary for erythrocytic invasion, and human protein CD36, a major receptor for P. falciparum-infected RBC's, are also under scrutiny: attention is focused also on plasmodium erythrocyte-binding antigens, which bind to RBC surface components. Genome-wide linkage and association studies are now carried out too, in order to identify genes associated with malaria resistance. Only a minor role is attributed to intravascular sickling, phagocytosis and haemolysis, while specific molecular mechanisms are the object of intensive research: among these a decisive role is played by a biochemical sequence, involving activation of haeme oxygenase (HMO-1), whose effect appears mediated by carbon monoxide (CO). A central role in protection from malaria is also played by immunological factors, which may stimulate antibody production to plasmodium antigens in the early years of life; the role of agents like pathogenic CD8 T-cells has been suggested while the effects of molecular actions on the immunity mechanism are presently investigated. It thus appears that protection from malaria can be explained by interaction of different factors: the elucidation of such mechanisms may prove valuable for the prevention and treatment strategy of a disease which still affects large parts of the world.

The formation of erythropoietic colonies from the peripheral blood of normal subjects, patients with primary proliferative polycythaemia (PPP) and primary thrombocythaemia (PT) was studied, using a chemically defined serum-free (S-) medium. Colony formation was markedly more prominent in the presence of burst-promoting activity (BPA) and erythropoietin (Ep) than with medium alone (P less than 0.001). In cultures using medium alone, significantly more PPP patients formed colonies than the control group (P less than 0.05). In the PT group this difference did not achieve statistical significance, but the mean BFU-E yield was significantly greater than in controls (P less than 0.05). In a separate series of experiments, parallel cultures in serum-containing (S+) and serum-free (S-) systems, in the presence of BPA and Ep did not show any significant difference in colony yield. The growth of 'endogenous' colonies in cultures with serum-free medium alone could be due to a peculiar sensitivity of erythropoietic progenitors to growth factors other than Ep.