The the higher the production of IL-6 through inducement via HT-7 the more severe the symptoms.
Linear Relationships between Patient Cytokine Responses and Symptoms of Fatigue and Pain
At baseline, the cytokine that had the strongest association with higher baseline fatigue in CFS patients was higher IL-6 (
r = +.43 and +.57 with physical fatigue and mental fatigue ratings,
p < .05). Higher baseline IL-6 was also associated with higher reported levels of physical fatigue at 48 h (
r = +.48,
p < .05). Predictive relationships between changes in cytokines/ligands at 8 h post-exercise (when greatest cytokine changes usually occurred) and SF severity at 48 h were also examined in all CFS patients using linear regression. Greater increases in IL-6 and in CD40L predicted greater increases in physical fatigue, accounting for 43% and 31% of the variance in fatigue increases, respectively (
p < .01; see
Figure 6), and increases in IL-6 also accounted for 29% of the variance in increased pain (
p < .01, not depicted). However, although the relationship with CD40L was robust, the relationships between IL-6 and both physical fatigue and pain increases were strongly influenced by the patient showing the largest IL-6 increase. When reexamined after removal of that individual, these relationships were no longer significant (
r = +.36,
R2 = 13%). Still, when considered together with the associations between higher baseline IL-6 and greater fatigue, these observations encourage continued research attention to IL-6 as well as CD40L in relation to SF.