The correct statements regarding psychoneuroimmunology and the immune system are: - (A): True. Leucocytes (white blood cells) identify and destroy pathogens like viruses. - (B): False. Stress does affect natural killer cell cytotoxicity, often decreasing their effectiveness. - (C): True. Stress can lead to the production of antibodies as part of the immune response. - (D): True. There are various types of leucocytes, including T cells, B cells, and natural killer cells, each with distinct roles in the immune system. - (E): False. B cells, not D-cells, are responsible for producing antibodies.