Blood cancers

Mass cytometry useful in measuring immune recovery after transplant

Mass cytometry has a role to play in immune profiling in HSCT patients and in other potential haematology applications, the 2017 HAA Annual Scientific Meeting has been told.

The technique can provide a wealth of data for global immunological assessment in patients and in discovering the fate of transferred cells in stem cell recipients.

Dr Emily Blyth, from Sydney’s Westmead Hospital, told the meeting mass cytometry was a more powerful form of cytometry.

Although both techniques use antibodies specific to intracellular and cell surface antigens, mass cytometry samples are conjugated to heavy metals instead of fluorophores.

“Cell samples are eventually turned into super-heated ionised plasma.  A mass spectrometer then looks at the presence of heavy metals and cellular components.

It is possible to detect to 40 cellular markers on every cell on every sample. The data was so complex new tools had to be developed,” Dr Blyth explained.

“Visualised T stochastic neighbour embedding is an mathematical algorithm applied to show the behaviour of different subsets of the immune system over time,” she said.

Blyth demonstrated its use in a third party T cell study.

“A non-randomised study was conducted using samples collected in adoptive cell therapies studies with virus-specific T cells to control vireamia in haemopoietic stem cell transplants.”

Three immune signatures were revealed across one healthy individual and two patients with very similar clinical characteristics.

However the patient outcome was very different – with one patient dying from CMV and the other patient had virological clearance with no ongoing problems with CMV.

Mass cytometry revealed the difference between the two patients.

She said patients with active CMV disease had very few CD4 and CD8 T cells.

“The patient who did not survive had more regulatory T cells and the majority of the cells were innate. NK cells were prominent. Three months later this patient had failed to develop any T cells whatsoever. CD8 and CD4 T cells were virtually absent.”

What was observed was a widespread reconstitution of immune cells, but most markedly CD8 T cells in CMV reactivation.

“The surviving patient who was able to clear the CMV had a large number of CD8 cells. This represents a super-physiological exaggerated response compared to the healthy individual.”

Dr Blyth said mass cytometry enabled the generation of a large data set from a small sample size.

“Basically the sky is the limit with the technique. The major limitation is the bioinformatics help because all this data came from a week of experiments and it’s a huge job to wade through it. However studies would be well served to have this type of analysis. ”

She added mass cytometry was also being used in melanoma research at the Ramaciotti Centre for Genomics.

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