Immunity is general term, together with its cells (general) it's called immune system. It's these cells that you call"Kinga", yani each immune cell has it's function. There are cells that protect the body against viral infections, there are some cells that protects the body against parasitic infection, there are some that protect against fungal infection and others protect against bacterial infection. So if I ask you the name of that thing you call "Kinga", I expect you to tell me the name of the specific cell which in this case is CD4+T cells.