Cellular Antigen Stabilising Reagent
History
TransFix® was developed by medical scientists from UK NEQAS, which is part of Sheffield Teaching Hospitals NHS Foundation Trust. TransFix® was developed out of the requirement to produce stabilised blood samples that could be used in External Quality Assurance programs for flow cytometry. The first publication on TransFix® as a cellular antigen stabilizing reagent was made in 1999 by D. Barnett et al.
TransFix® has been in circulation in the research world from 1999 until the present day, generating a number of scientific publications. In 2005 the Sheffield Teaching Hospitals NHS Foundation Trust licensed TransFix® to Cytomark in order to make it more generally available to the clinical and scientific world.
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Fresh Blood Samples |
TransFix® Blood Sample |
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Flow Cytometry comparison of fresh whole blood with a TransFix® stabilised sample at Day10 demonstrates that TransFix® stabilised whole blood has the same flow cytometry staining pattern as seen in fresh whole blood. Staining examples with CD45-PE-Cy5 and CD3 FITC antibodies are shown above. |
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Applications
Immunophenotyping by flow cytometry is an established diagnostic tool to assess the type and number of lymphocytes in human blood. Situations often arise where samples cannot be analysed immediately after being taken and must be preserved for future analysis. TransFix® preserves leucocyte stability and the antigenic sites, until flow cytometry can be performed. This enables blood samples to be batched for subsequent analysis or to be transported between distal sites.
TransFix® can be used to extend the viability of anticoagulated blood samples for up to 10 days when stored at 4ºC. Research has also demonstrated (Bergeron et al) that blood samples treated with TransFix® are also stable when stored between 20ºC to 24ºC for up to 7 days and at 37ºC for up to 3 days. TransFix® can be used in resource poor areas of the world to extend sample viability without refrigeration and enable samples to be batched and transported for examination. (Jani et al, 2001).
CD4+/CD8+ counting for management of HIV/AIDS
Monitoring CD4+ and CD8+ cell counts has become essential in monitoring healthy individuals and patients infected with HIV/AIDS.
TransFix® is mixed with whole blood at a ratio of 1:5 offering the benefit of minimal sample dilution. Absolute counts from blood samples treated with TransFix® must be adjusted for the dilution factor by dividing by 0.8.
Transportation of samples between clinical sites raises concerns about sample integrity. Primary CD4+ gating can be performed on blood samples treated with TransFix® with great precision.
Shipping and handling of HIV+ samples involves inherent elevated costs and a risk of exposure to HIV. The addition of TransFix® results in a significant reduction in HIV replication. (Kim et al, 2001). However, samples must still be handled with universal precaution protocols.
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Fresh Blood Samples |
TransFix® Blood Sample |
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Flow Cytometry comparison of fresh whole blood with a TransFix® stabilised sample at Day10 demonstrates that TransFix® stabilised whole blood has the same flow cytometry staining pattern as seen in fresh whole blood. Staining examples with (CD3 FITC and CD4 APC) and (CD3 FITC and CD8 PE) antibodies are shown above. |
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Immunophenotyping
Subsets of leucocytes can be distinguished on the basis of cell surface antigens using flow cytometry. Quantitative and qualitative changes in leucocyte sub sets are used to identify and monitor haematologic diseases. TransFix® has been shown to preserve a wide range of cellular markers (Barnett et al, 1999) for up to 10 days. A full haematological profile can also be obtained up to 7 days after the addition of TransFix®.
Other Species
TransFix® has been shown to be effective in stabilizing the cellular antigenic profile of mouse, rat and sheep blood.