Dr. blackman studies the interconnections among psychological processes, the nervous and endocrine systems, and the immune system. like other specialists in the field of psychoneuroimmunology, dr. blackman is aware that researchers have discovered all except that

The possible answers are :
1.lymphocytes themselves produce neurotransmitters and hormones.
2.the surfaces of lymphocytes contain receptor sites for neurotransmitters and hormones, including catecholamines and cortisol.
3.the immune system and the central nervous system are only remotely related to one another.
4.the central nervous system and the immune system are directly linked.

The answers 1 and 3 are not true.

The central nervous system and the immune system are directly linked and in constant communication. The central nervous system can trigger hormone and immune responses to various factors like stress, inflammation or neurological disease. The lymphocytes have receptors for neurotransmitters and hormones, but they can not produce them themselves.

Ithink the dna sequences may vary but the amino acid sequences are identical.