Assays of the circulating immune cells, inflammatory cytokines (interleukin-6 and tumor necrosis factor-alpha), as well as plasma immunoglobulin G (IgG) in healthy volunteers, were used to investigate the relationship between personal biochemistry and well-being.

The analysis of humoral and cellular immune markers in healthy volunteers who reported no physical symptoms of disease, suggests that the “feel-good factor” may positively affect the strength of an individual’s immune system and their ability to keep illness at bay. The research saw no significant difference between men and women.

• Is Self-Rated Health Associated with Blood Immune Markers in Healthy Individuals?
  A. Nakata, M. Takahashi, Y. Otsuka, N. Swanson,
  Int. J. Behavioral Med. 2010, 17.
  DOI: 10.1007/s12529-010-9102-0