This is touching.
Redgrave and Natasha's sister Joely Richardson are co-chairing the event.
Natasha Richardson was on the board of trustees since 2006 and was a passionate advocate for AIDS research as her father Tony Richardson died from AIDS-related complications back in 1991.
The black-tie event and auction will include performances by Lady GaGa and Rufus Wainwright.
Natasha left behind her husband Liam Neeson and their two sons Michael and Daniel after suffering a fatal brain injury while skiing in Quebec.
[Image via Daniel Deme / WENN.]