When a group of proteins such as interferons and interleukins are released by the t cells

the cells act as intracellular signals to begin the immune response

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.