Complex sentence: Gut flora could also impact severe immunodeficiency in HIV disease, two thirds of all T cells reside in the lymphoid tissue of the gut, where the human immunodeficiency virus spreads after exposure, even before it shows up in blood.
Split into simpler sentences: Gut flora could also impact severe immunodeficiency in HIV disease. Two thirds of all T cells reside in the lymphoid tissue of the gut, where the human immunodeficiency virus spreads after exposure, even before it shows up in blood.