Jim Al-Khalili talks T cells, our immune response and Long Covid with Prof Danny Altmann. Danny Altmann joined ‘team T cells’ in his twenties and has been studying how these killer operate ever since. How do they know which cells to search and destroy? The T cell wing of our immune response is highly targeted and incredibly clever, on a par with the most sophisticated military intelligence operation and in recent decades there have been dramatic advances in our understanding of how it all works . Danny tells Jim how he came to study our immune response to all sorts of pathogens, from anthrax to zika, why he spends every morning from 5 to 6am in the bath reading 19th century classics and why he’s determined to try and understand Long Covid. Producer: Anna Buckley