Trogocytosis — sounds like something out of Lord of the Rings.  The word comes from the Greek trogo meaning nibble — I didn’t think Greeks had words for such trivial things.

But don’t laugh, trogocytosis is intimately involved in the immune system, and diminishing it may be a way to treat cancer.

So what is Trogocytosis?  It is the transfer of membrane fragments between two cells in physical contact.  This includes proteins embedded in the membrane.

[ PNAS vol. 118 e2110241118 ’21n ] tells us that human colon cancer cells can use trogocytosis to acquire attacking lymphocyte proteins, such as the immune regulatory proteins CTLA4 and Tim3.  Capturing these proteins allows the cancer to turn off the immune response against it.  This may be where part of the immunosuppressive tumor microenvironment comes from.

Neuroscientists and clinicians will be interested to know that trogocytosis is the process by which microglia phagocytose dendritic spines and synapses in the process of synaptic pruning. [ Proc. Natl. Acad. Sci. vol. 118 pp. 17605 – 17607 ’09 ].

Trogocytosis is important in immune system function, it is how dendritic cells transfer MHC class I antigen peptide complexes to other cells.  This allows direct transfer of preformed antigen/peptide complexes from an infected to to an antigen presenting cell without the need of further processing [ Nature vol. 471 pp. 581 – 582, 629 – 632 ’11 ].  It was a simpler time 10 years ago, this was also called cross-dressing.

So trogocytosis has its fingers in many pies, and inhibiting it to decrease the immunosuppressive tumor microenvironment is likely to have many other consequences — you heard about some of them here.

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