Trogocytosis

Trogocytosis ("greek ‘trogo’ = gnaw") is an active transfer phenomenon of lymphocytes (B, T and NK cells) conjugating to "antigen" presenting cells, to extract surface molecules from them. This conjugation is also called “immunological synapse”.

Besides conjugation Trogocytosis involves the transfer of plasma membrane fragments from the presenting cell to the lymphocyte and has been documented in T, B and natural killer cells, in vivo and in vitro. Trogocytosis is specifically triggered by antigen receptor signalling and might be important for the induction of regulation of "immune responses" and possibly for the control of other cellular systems. Trogocytosis by cytotoxic T lymphocytes might consequently contribute to the selection of high affinity T-cells. With extremely high concentrations of MHC-I-restricted antigenic peptide added externally to target cells, trogocytosis occurs as “fratricide” of cytotoxic T lymphocytes, which bound antigenic peptide loaded MHC molecules by their own T cell receptor.

Acquired molecules, such as regulatory molecules with extracellular or intracellular components might alter the lymphocytes activity and direct several lymphocyte functions, such as migration to the adequate injured tissues. Such gained plasma membrane fragments could also contribute to the capacity to proliferate, because lipids are highly energetic claiming components to establish. Trogocytosis might have appeared first in very primitive organisms to feed off other cells.

(E. Joly, D. Hudrisier 2003)

Trogocytosis by Granulocytes

Like in lymphocytes trogocytosis occurs with PMN (polymorph nuclear granulocytes) and is associated with effective ADCC (Antibody dependent cell mediated cytotoxicity).It was shown to initiate ADCC in vitro, PMN have to adhere to their target cells so they make intimate contacts with antibody obsonized tumor cells. This cell clustering precedes mutual membrane lipid exchange between effector and target cell during ADCC and does not happen in the absence of obsonizing antibodies.

(Horner, Frank, Dechant, Repp, Glennie, Martin Herrmann & Stockmeyer 2007)