Elimination of clonogenic stem cells from human multiple myeloma cell lines by a plasma cell-reactive monoclonal antibody and complement

The monoclonal antibody (MoAb) MM4 reacts with human multiple myeloma (MM) cell lines and bone marrow from patients with plasma cell dyscrasias but not with normal peripheral blood or bone marrow cells. Treatment with MM4 and rabbit complement (C') was cytotoxic to the plasma cell-derived cell lines GM 1312, RPMI 8226, and ARH-77, as demonstrated by chromium release microcytotoxicity and trypan blue exclusion assays. The same treatment eliminated greater than 99% of clonogenic myeloma stem cell colony formation of these cell lines, with less than 20% inhibition of normal human bone marrow pleuripotent progenitor colony formation in vitro. As an experimental model to explore the efficacy of MM4 + C' in purging MM-involved bone marrow, normal marrow cells were mixed with RPMI 8226 or GM 1312 cells in the ratio of 90:10 or 50:50 (marrow:myeloma cells). Colony growth assays indicated that MM4 + C' eliminated at least 2 logs of clonogenic myeloma stem cells in both 90:10 and 50:50 preparations, while sparing the majority of normal marrow progenitors (inhibition of CFU-C:10% to 13%; BFU-E:0%). The selectivity of MM4-mediated cytotoxicity may be useful for eliminating myeloma clonogenic stem cells from bone marrow of patients with multiple myeloma.     

Limitations of flow cytometry in the analysis of CDIalHLADR+ human oral mucosal Langerhans cells

Suspensions of human oral epithetial cells were stained with antibodies to CD la and HLADR conjugated with fluorochromes and analysed by flow cytometry with the aim of purifying double-labetled Langerhans cells, a population comprising approximatety 2% of the cell total. Whole suspensions had high levets of autofluorescence and a wide range of forward and right angle scatter properties. The mean percentage of CDIalHLADR+ cells was 2.I%, though the double-labetled cells did not form a discrete group and the percentages of positive cells using control antibodies were similar. Density gradient centrifugation prior to flow cytometry did not facilitate Langerhanr cell identification within the suspension. The results indicate flow cytometric analysis of minority cell populations (such as Langerhans cells) within oral epithetium is limited by the autofluorescence of physically heterogeneous keratinocytes, and emphasise the importance of controls in studies of oral epithetium which use this method.     

The Influence of Heat Treatment on the Mechanical Properties and Corrosion Resistance of the Ultrafine-Grained AA7075 Obtained by Hydrostatic Extrusion

In this paper, the corrosion resistance and mechanical properties of the 7075 aluminum alloy are studied. The alloy was deformed by hydrostatic extrusion and then aged both naturally and artificially. Results are compared with those of coarse-grained material subjected to T6 heat treatment. The aim of the research is to find the optimal correlation between the mechanical properties and the corrosion resistance of the alloy. To this end, static tensile tests with subsequent fractography, open circuit potential, and potentiodynamic polarization tests in 0.05 M NaCl were conducted. Obtained results show that a combination of precipitate hardening and a deformed microstructure leads to increased mechanical strength with high anisotropy due to the presence of fibrous grains. Plastic deformation increases susceptibility to corrosion due to the increased number of grain boundaries, which act as paths along that corrosion propagates. However, further artificial aging incurs a positive effect on corrosion resistance due to changes in the chemical composition of the matrix as a result of the precipitation process.