Robin Coombs: his life and contribution to haematology and transfusion medicine.

Robin Coombs was the last survivor of the distinguished group of immunologists that included Philip Gell, John Humphrey, John Marrack, Peter Medawar and Robert White and who were responsible for the renaissance of British Immunology after the Second World War. He is best remembered for describing the antiglobulin test that bears his name. The antiglobulin test revolutionised the diagnosis of haemolytic diseases and the compatibility testing of blood for transfusion. In all, Coombs authored over 200 scientific papers. Haemagglutination reactions became widely used in the diagnosis of a range of infectious agents. Together with Philip Gell, he devised the classification of allergic reactions; these were published in the textbook "Clinical Aspects of Immunology", which he and Gell first edited in 1963 and which became the leading textbook on medical immunology. Robin Coombs was also one of the founders of the British Society for Immunology.

Immunotherapeutic strategies in acute lymphoblastic leukaemia relapsing after stem cell transplantation.

Acute lymphoblastic leukaemia (ALL) responds well to chemotherapy and the majority of children and a significant proportion of adults are cured of their disease after primary therapy. However, a number of patients relapse and allogeneic transplantation following conditioning with chemotherapy and radiotherapy offers the possibility of long-term survival in a proportion of these patients. A significant number of patients with ALL develop disease that is refractory to further therapy. The infusion of unmodified donor lymphocytes (DLI) following relapse after allogeneic transplantation has been shown to be curative in patients with chronic myeloid leukaemia (CML). However, in ALL the success rate is much lower. The results of in vitro and limited in vivo studies suggest that it may be possible to manipulate lymphocytes from the transplant donor to produce cytotoxic T-lymphocytes (CTL) with increased effectiveness in killing patients' ALL cells. This may be done in a number of ways. For example, some strategies utilise the patients dendritic cells (DC) to present tumour antigens to donor lymphocytes and convert them into CTL either by pulsing DC taken in remission with ALL cells or lysate, fusing such 'normal' DC with ALL cells or using DC cultured from the patient's ALL cells. Other approaches include exploiting the expression of leukaemia-specific antigens such as the proteinase PR-3 or the zinc finger transcription factor Wilms tumour-1 protein (WT-1) to stimulate CTL responses. Alternatively, immunotherapeutic strategies might exploit differences in minor histocompatibility antigens such as HA-1 and HA-2 between donor and recipient. These are expressed solely on haemopoietic cells making them suitable targets for donor derived anti-leukaemic cells. In vivo studies to date suggest that educated T-cells may have a role to play in the treatment of relapsed and refractory ALL in the future.

Characterization of acute lymphoblastic leukemia progenitor cells.

Only some acute lymphoblastic leukemia (ALL) cells are thought to be capable of proliferating to maintain the leukemic clone, and these cells may be the most relevant to target with treatment regimens. We have developed a serum-free suspension culture (SC) system that supported growth of B-ALL cells from 33 patients for up to 6 weeks. ALL cells from 28 cases (85%) were expanded in this system, and growth was superior in SC than in long-term bone marrow culture. To characterize ALL progenitors, cells were sorted for expression of CD34 and CD10 or CD19 and the subfractions assayed in SC and in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. Cells capable of long-term proliferation in vitro and NOD/SCID repopulation were derived only from the CD34(+)/CD10(-) and CD34(+)/CD19(-) subfractions, and these cells could engraft secondary recipients. The engrafted cells had the same immunophenotype and karyotype as was seen at diagnosis, suggesting they had differentiated in vivo. These results demonstrate that ALL cells capable of long-term proliferation in vitro and in vivo are CD34(+)/CD10(-)/CD19(-). This suggests that cells with a more immature phenotype, rather than committed B-lymphoid cells, may be the targets for transformation in B-ALL.

The use of stimulated granulocyte transfusions to prevent recurrence of past severe infections after allogeneic stem cell transplantation.

The predictable neutropenia that follows allogeneic stem cell transplantation (ASCT) may be associated with recurrence of previous life-threatening infection. We describe nine patients with either previous invasive aspergillosis (IA) or considered to be at high risk of developing IA who underwent ASCT with prophylactic granulocyte transfusions. The study group, when compared with a control group, had a significant reduction in the incidence and duration of fevers (P < 0.05) and maximum C-reactive protein (P < 0.05). There were significantly fewer days of neutropenia (P < 0.05). There was also radiological improvement of pulmonary infiltrates in four out of seven assessable patients. No serious toxicity was encountered in donors or recipients. We conclude that prophylactic granulocyte donations can be given safely, and that they significantly reduce the number of days of neutropenia. Further investigation is warranted to determine whether granulocyte donations can prevent the recurrence of IA in patients at risk of fungal infection.

Detection of residual donor leucocytes in leucoreduced red blood cell components using a fluorescence microplate assay.

In November 1999, universal leucoreduction of blood components was introduced in the UK to minimise the risk of variant Creutzfeldt-Jakob Disease (vCJD) transmission by blood transfusion. The UK specifications for leucodepletion processes state that 99% of leucodepleted components should contain < 5 x 10(6) leucocytes/unit, within 95% confidence limits. However, this leucocyte concentration is below the detection limits of standard haematology analysers. The development of a fluorometric immunoassay to detect the residual donor leucocytes in leucoreduced blood components is described. Monoclonal antibodies to leucocyte-specific cell surface antigens, CD45 and CD15, were adsorbed to the well surface in 96-well microplates. Red blood cell samples containing low numbers of leucocytes were added to the wells and the cells of interest captured by the monoclonal antibodies. Since leucocytes are the only nucleated cells found in significant numbers in blood components they were quantified using PicoGreen, a fluorescent stain specific for dsDNA. In comparison to flow cytometry, the method currently used to detect low numbers of leucocytes, the microplate assay demonstrated excellent sensitivity (1.00) and acceptable specificity (0.81) when standard leucodepleted samples were tested. There was no significant difference between the two methods (p < or = 0.175). In conclusion, the fluorescence microplate assay represents a simple, high throughput alternative to flow cytometry for monitoring leucodepletion compliance in blood banks.

Ex vivo expansion of megakaryocyte progenitor cells from normal bone marrow and peripheral blood and from patients with haematological malignancies.

A number of haematological and non-haematological malignancies can be successfully treated using high-dose chemotherapy +/- irradiation followed by haematopoietic progenitor cell transplantation. Post transplant, thrombocytopenia and neutropenia always occur and patients require platelet transfusions. It may be possible to reduce the period of thrombocytopenia by re-infusion of ex vivo expanded megakaryocyte progenitors (MP), derived from the progenitor cell graft. We have investigated the expansion of MP from CD34+ enriched cells from normal bone marrow (NBM) and peripheral blood (PB) and remission BM or PB samples from patients with haematological malignancies. CD34+ cells were cultured in serum-free medium supplemented with thrombopoietin (TPO), interleukin 1 (IL-1), IL-6 and stem cell factor (SCF) for 7 d, then cell proliferation was assessed by flow cytometry using lineage-specific markers. It was possible to significantly expand the number of MP cells from all sources. There were no major differences in yields of MP from normal BM or PB, or BM from multiple myeloma and non-Hodgkin's lymphoma patients. However, expansion of MP in acute myeloid leukaemia samples was lower than all other samples and the number of megakaryocyte colony-forming units was reduced. Several cytokine combinations were evaluated to optimize MP expansion from NBM. Equivalent yields of MP were obtained using TPO and one of IL-1, IL-3, granulocyte-macrophage colony-stimulating factor or SCF, suggesting that large cytokine combinations are not necessary for this procedure. It should be possible to scale up the culture conditions described to produce effective MP doses for clinical transplantation.