Longitudinal analysis of immune abnormalities in varying severities of Chronic Fatigue Syndrome/Myalgic Encephalomyelitis patients

Abstract

Background: Research has identified immunological abnormalities in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME), a heterogeneous illness with an unknown cause and absence of diagnostic test. There have been no CFS/ME studies examining innate and adaptive immune cells longitudinally in patients with varying severities. This is the first study to investigate immune cells over 6 months while also examining CFS/ME patients of varying symptom severity.

Methods: Participants were grouped into 18 healthy controls, 12 moderate and 12 severe CFS/ME patients and flow cytometry was used to examine cell parameters at 0 and 6 months.

Results: Over time, iNKT CD62L expression significantly increased in moderate CFS/ME patients and CD56(bright) NK receptors differed in severe CFS/ME. Naïve CD8(+)T cells, CD8(-)CD4(-) and CD56(-)CD16(-) iNKT phenotypes, γδ2T cells and effector memory subsets were significantly increased in severe CFS/ME patients at 6 months. Severe CFS/ME patients were significantly reduced in CD56(bright)CD16(dim) NKG2D, CD56(dim)CD16(-) KIR2DL2/DL3, CD94(-)CD11a(-) γδ1T cells and CD62L(+)CD11a(-) γδ1T cells at 6 months.

Conclusions: Severe CFS/ME patients differed from controls and moderate CFS/ME patients over time and expressed significant alterations in iNKT cell phenotypes, CD8(+)T cell markers, NK cell receptors and γδT cells at 6 months. This highlights the importance of further assessing these potential immune biomarkers longitudinally in both moderate and severe CFS/ME patients.

Fig. 1

Average severity scale scores at 0 and 6 months for control, moderate and severe CFS/ME patients. a Dr Bells Disability Scale scores for each group, represented as a score between 0 and 100. b Karnofsky Performance Scale scores for each group, represented as a score between 0 and 100. All data is presented as mean ± SEM where statistical significance was accepted as p < 0.05. CFS/ME Chronic Fatigue Syndrome/Myalgic Encephalomyelitis, SEM standard error of the mean

Fig. 2

iNKT cell expression of CD62L in control, moderate and severe CFS/ME patients at 0 and 6 months. iNKT cells expressing CD62L as a percentage of total iNKT cells. Data is presented as mean ± SEM where statistical significance was accepted as p < 0.05. CFS/ME Chronic Fatigue Syndrome/Myalgic Encephalomyelitis, SEM standard error of the mean

Fig. 3

iNKT cell expression profile in control, moderate and severe CFS/ME patients. a iNKT cells expressing a CD8⁻CD4⁻ phenotype as a number of total iNKT cells (cells/μL). b iNKT cells expressing a CD56⁻CD16⁻ phenotype as a number of total iNKT cells (cells/μL). Data is shown as mean ± SEM where statistical significance was accepted as p < 0.05. CFS/ME Chronic Fatigue Syndrome/Myalgic Encephalomyelitis, SEM standard error of the mean

Fig. 4

Alterations in CD56^bright NK cell receptors between 0 and 6 months in control, moderate and severe CFS/ME patients. a Percentage of CD56^brightCD16^dim NK cells expressing KIR3DL1/DL2. b Percentage of total CD56^brightCD16⁺ NK cells expressing KIR2DL1. c Percentage of CD56^brightCD16⁺ NK cells expressing KIR2DL2/DL3. d Percentage of CD56^brightCD16⁺ NK cells expressing KIR2DS4. Data is shown as mean ± SEM where statistical significance was accepted as p < 0.05. NK Natural Killer, CFS/ME Chronic Fatigue Syndrome/Myalgic Encephalomyelitis, SEM standard error of the mean

Fig. 5

NK cell receptors in control, moderate and severe CFS/ME participant groups. a Percentage of total CD56^brightCD16^dim NK cells expressing the receptor NKG2D. b Percentage of total CD56^dimCD16⁻ NK cells expressing the receptor KIR2DL2/DL3. Data is shown as mean ± SEM where statistical significance was accepted as p < 0.05. NK Natural Killer, CFS/ME Chronic Fatigue Syndrome/Myalgic Encephalomyelitis, SEM standard error of the mean

Fig. 6

Increased naïve CD8⁺ T cells in the severe CFS/ME participant group. Number of total CD8⁺ T cells (cells/μL) of the naïve CD8⁺ T cell subset in controls, moderate CFS/ME and severe CFS/ME. Data is shown as mean ± SEM where statistical significance was accepted as p < 0.05. CFS/ME Chronic Fatigue Syndrome/Myalgic Encephalomyelitis, SEM standard error of the mean

Fig. 7

Alterations in γδ2 T cell phenotypes in control, moderate CFS/ME and severe CFS/ME patients. a Total number of γδ2 T cells expressed as total cells/μL. b Total number of γδ2 T cells (cells/μL) expressing the effector memory cell phenotype. c Total number of γδ2 T cells (cells/μL) expressing the CD45RA⁺ effector memory cell phenotype. Data is shown as mean ± SEM where statistical significance was accepted as p < 0.05. CFS/ME Chronic Fatigue Syndrome/Myalgic Encephalomyelitis, SEM standard error of the mean

Fig. 8

Profile of γδ1 and γδ2 T cell expression of receptors and adhesion molecules in control, moderate CFS/ME and severe CFS/ME patients. a γδ1 T cells with the expression CD94⁻CD11a⁻, as a number of total γδ1 T cells (cells/μL). b γδ2 T cells with the expression CD94⁻CD11a⁻, as a total number of γδ2 T cells (cells/μL). c γδ2 T cells with the expression CD94⁻CD11a⁺, as a total number of γδ2 T cells (cells/μL). d γδ1 T cells expressing CD62L⁺CD11a⁻ as a total number of γδ1 T cells (cells/μL). e γδ2 T cells expressing CD62L⁺CD11a⁻, as a total number of γδ2 T cells (cells/μL). f γδ2 T cells with the expression CD62L⁺CD11a⁺, as a total number of γδ2 T cells (cells/μL). Data is shown as mean ± SEM where statistical significance was accepted as p < 0.05. CFS/ME Chronic Fatigue Syndrome/Myalgic Encephalomyelitis, SEM standard error of the mean