Thursday, July 23, 2015

Antigen-specific NK cell memory

This study was done on rhesus macaques. Purified NK cells were sorted from spleen, liver or blood. Autologous, virus infected or antigen-pulsed DCs were used as targets. Control DCs were either uninfected or mismatched antigen-pulsed.

Initially, the authors observed that purified spleen (c) or hepatic (d) NK cells from SHIV-infected hosts showed cytotoxic response to Gag and Env, but not OVA pulsed autologous DCs.

Similarly, purified splenic NK cells derived from SIV-infected hosts showed antigen-specific cytotoxicity (a, b). Interestingly, blood derived NK cells showed no cytotoxic activity against antigen-pulsed DCs (c).   

Finally, the authors showed that splenic (c) and hepatic (d) NK cells derived from hosts vaccinated 5 years earlier displayed vaccine-matching antigen-specific DCs lysis. Here too, blood derived NK cells showed minimal antigen-pulsed DCs lysis (e).

Additional results indicated that NK-mediated lysis of antigen-pulsed DCs were mediated via NKG2C or NKG2A pathways. These NK receptors recognize MHC class I molecules loaded with leader peptides derived from other endogenous MHC molecules. However, it is not clear how this mechanism confers exogenous antigen-specific memory to NK cells.

In summary, these results suggest that NK cells could mount antigen-specific memory response. 

David Usharauli 

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