Hematopoietic recovery following PBSC is dependent on progenitor-cell number infused and affect of previous chemotherapy on progenitor quality. Progenitor-cell mobilization is adversely affected by prior radiotherapy. The minimum threshold of GM-CFC required is achieved in most patients with a single apheresis, but an optimal collection usually requires at least two harvests.

The incidence of lymphopenia, thrombocytopenia and neutropenia was studied in 105 homosexual men with HIV infection. Lymphopenia was common in patients with AIDS (75%), but its incidence in PGL (24%) was not significantly different from that in asymptomatic anti-HIV positive (15%) homosexual men. Neutropenia and thrombocytopenia were found in patients with AIDS or PGL, but not in asymptomatic anti-HIV positive homosexuals. The study suggests that the neutropenia and thrombocytopenia in these patients were due to autoimmune destruction of neutrophils and platelets.

A simplified mobilization protocol is described that requires only one apheresis to achieve rapid hematologic engraftment.

Summary. Acute myeloid leukaemia (AML) with the t(8;21)(q22;q22) is deemed to be a 'good-risk' disease. 396 patients with AML at diagnosis were screened for the presence of t(8;21) and AML1/ETO fusion transcripts by cytogenetic and RT-PCR techniques respectively. 32 cases of t(8;21) were detected, all of which were also PCR positive. A further 19 cases were detected at the molecular level, predominantly but not exclusively in M1 and M2 FAB types. Approximately 12% of all new cases of AML are estimated to have AML1/ETO fusion transcripts and it is suggested that molecular screening should be performed in all cases with the possible exception of the M3 FAB type.

Summary. It has been established that cytogenetic findings at diagnosis of acute myeloid leukaemia (AML) are a powerful prognostic indicator. Patients who have the inv(16)(p13q22), closely associated with the FAB subtype M4Eo, are deemed to have good-risk disease. This subtle translocation may be difficult to detect in poor-quality metaphase preparations and if missed could lead to the incorrect assignment of risk group and influence further treatment strategies.We studied 321 patients with AML at diagnosis for the presence of inv(16)(p13q22) and CBFb/MYH11 fusion transcripts by cytogenetic and RT-PCR techniques respectively. Karyotypic analysis detected 21 cases of inv(16) (p13q22), all of which were PCR positive. A further 12 cases were detected at the molecular level only, in FAB types other than M4Eo. The observed frequencies of CBFb/MYH11 fusion transcripts in our study have been adjusted for the reported incidence of each FAB subtype and we calculate that 10 . 1% of all new cases of AMLs have molecular evidence of inv (16)(p13q22), only half of which are of the M4Eo subtype.We conclude that molecular screening for the presence of CBFb/MYH11 fusion transcripts should be mandatory in all cases of AML at diagnosis.Keywords: AML, inv(16)(p13q22), CBFb/MYH11, prognosis.The chromosomal abnormality inv(16)(p13q22) is most closely associated with the distinct subtype of acute myelomonocytic leukaemia with bone marrow eosinophilia (AML M4Eo) (Le Beau et al, 1983) and although the eosinophilia is variable it has been shown to be part of the leukaemic cell population. This pericentric inversion and the t(16;16)(p13;q22) produce a transcriptionally active fusion gene (5 0 -CBFb/MYH11-3 0 ) derived from the CBFb and MYH11 genes at 16q22 and 16p13 respectively. The reciprocal 5 0 -MYH11/CBFb-3 0 product is expressed in a proportion of cases only. The 5 0 -CBFb/MYH11-3 0 chimaeric protein is believed to induce leukaemic transformation by its abnormal interaction with the DNA-binding protein coded by the AML1 gene, thus altering target genes usually regulated by the CBFb/AML1 transcription factor complex .It has now been established from analysis of data from the MRC AML 10 trial and other international groups that AML patients with the inv(16)(p13q22) translocation, together with those in which the t(15;17)(q22;q21) or t(8;21) (q22;q22) are seen, have a favourable prognosis (Burnett et al, 1995), with the main benefit seeming to be in diseasefree survival (DFS) which leads to a better overall survival. This has been incorporated into the ongoing AML 12 trial where good-prognosis patients are spared bone marrow transplantation in first complete remission (CR). It is therefore highly desirable to define those patients who possess these favourable translocations, either by routine cytogenetic investigations or by testing at the molecular level. This may give prognostic information and also provide a means of minimal residual disease evaluation. Conventional cytogenetic methods, including synchronization and Giemsa banding, ...