The answer could be 5.4, 5 2/5, or 27/5.
Epithelial, muscle, connective, nerve and blood.
The immune system and the nervous system maintain extensive communication, including 'hardwiring' of sympathetic and parasympathetic nerves to lymphoid organs. Neurotransmitters such as acetylcholine, norepinephrine, vasoactive intestinal peptide, substance P and histamine modulate immune activity.