The CD34+ purified grafts were enriched in stem/progenitor cells, with five of these 10 preparations containing > or = 94% CD34+ cells. Engraftment with CD34(+)-purified cell grafts as pure as 99% confirms that autologous CD34+ cells, alone, are sufficient to provide hematopoietic rescue for myeloablated patients. The best purification results were obtained on small marrow harvests from patients with neuroblastoma. The engraftment of highly purified CD34+ cells obtained by this technology and the antitumor effect of the transplant, by which two of 10 poor prognosis patients remain clinically free of tumor, have stimulated further clinical trials.

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Resistance to the protozoan parasite Trypanosoma cruzi is governed by multiple genetic factors, including at least one coded for by a locus in or neat the major histocompatibility complex of the mouse. The influence of the H-2 locus on resistance was evident when H-2 congenic mice on a strain background of intermediate resistance were challenged or when the survival of H-2 typed F2 mice was followed. The H-2k haplotype of the susceptible C3H/An strain was associated with higher mortality when compared with the H-2b haplotype of the resistant C57BL/10 strain. Genetic studies showed that resistance was a dominant trait and increased with genetic heterozygosity. Fl mice derived from crosses between resistant and susceptible strains, or even between two susceptible strains, were much more resistant than either parent. Crosses between two resistant strains, C57BL/6J and DBA/2J, led to resistant progeny in the Fl and F2 generations; but when recombinant inbred strains derived from these parental strains were challenged, susceptible strains were identified, indicating that different genes were responsible for resistance in the two strains.

A procedure is described for the measurement of the %CD34+ progenitor cells in bone marrow using directly conjugated antibodies. Staining cells with anti-CD45.FITC in conjunction with anti-CD34.PE allows the CD45- nucleated red blood cells and the CD45++ lymphocytes and monocytes to be separated from the CD45+ progenitor cells. Granulocytes are separated from the CD34+ cells based on differences in side scatter properties. A gated acquisition of CD34+ cells is used to define the boundaries of the CD34+ population in a plot of forward scatter vs side scatter and in a plot of anti-CD45.FITC vs anti-CD34.PE. Use of these regions during analysis reduces background staining and allows for a consistent identification of a CD34+ population. Acquisition of 50,000 cells provides adequate precision of the %CD34+ measurement. Acquisition and analysis procedures are presented for use of both a Becton Dickinson FACScan flow cytometer and a Coulter EPICS Profile II flow cytometer.

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