SUMMARYEarlier results indicating that vaccinia virus entered L cells by a process of direct fusion between the virus envelope and the plasma membrane of the cell have been confirmed and extended using immuno-ferritin conjugates to locate virus antigens on the host cell surface. After fusion, components of the virus envelope become rapidly dispersed in the plasma membrane. Fusion has also been observed as the predominant mode of entry of vaccinia virus into HeLa cells.

The Australian Multi-centre study on CD34+ cell quantitation by flow cytometry documented, first, the extent of variation of CD34+ cell enumeration and, second, the influence of flow cytometric gating on CD34+ cell measurement. A PBSC harvest analyzed by 20 participating centers showed results ranging from 0.64% to 2.80%, with a median of 1.54% CD34+ cells. Of 20 centers, 9 obtained results within +/-10% of the median (the criteria for reproducibility suggested by the ISHAGE Guidelines). The flow cytometric gating strategy was identified as one of the major variables among the methods used. In stage 2, list mode data from two samples were analyzed by 24 Australian and overseas centers, including the authors of three published guidelines. Significantly different CD34+ results were obtained when different gating strategies were used (p < 0.006). When all the centers used the same gating strategy, the measurement of CD34+ cells fell within a narrow range, with 0-7% of results outside +/-10% of the median. However, when different gating strategies were used, the results were more widely scattered, with 17% of centers outside +/-10% of the median. This study demonstrated the potential impact of flow cytometric gating strategy on the reproducibility of CD34+ cell enumeration.

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Summary Antisera produced against either whole leptospiral cells or purified axial filament (AF) both possessed agglutinating activity towards live cultures and precipitated AF in gel diffusion reactions. The anti‐cell serum possessed, in addition, precipitating activity to an unideutified antigen when reacted against a crude preparation of AF. The AF antigen was heat‐labile; a suspension of boiled cells was used to absorb out antibodies to heat‐stable somatic antigens. This absorption resulted in a drop in the agglutinating titre in both the anti‐cell and anti‐AF sera, but residual agglutinating activity was always present after repeated absorptions. After absorptions, both of the antisera reacted only with AF antigen in precipitation with crude AF extracts. The anti‐cell sera showed immobilising activity which was apparently a secondary effect resulting from damage to the cell by anti‐somatic antibodies. The anti‐AF sera showed some, but not strong, immobilising activity. The absence of complete immobilisation dees not necessarily exclude the AF from a role in motility. Treatment with anti‐cell serum resulted in degradation of the leptospiral cell structure seen firstly in the enveloping sheath, followed by the protoplasmic cylinder and, finally, lysis. Treatment with specific anti‐AF serum did not lead to degradation or lysis of the cells.