Altered functional B cell subset populations in patients with chronic fatigue syndrome compared to healthy controls

Abstract

Chronic fatigue syndrome (CFS) is a heterogeneous disorder of unknown aetiology characterized by disabling fatigue, headaches, sleep disturbance and several other symptoms. The onset of CFS may follow a viral infection or period of stress. Patients with CFS do not have hypogammaglobulinaemia, predisposition to recurrent bacterial infections or symptoms of autoimmunity. To date, defects in B cell numbers or function have not been shown in the literature. However, treatment with anti-B cell therapy using Rituximab has recently shown benefit to CFS patients. We therefore postulated that patients with CFS had a subtle humoral immune dysfunction, and performed extended B cell immunophenotyping. We undertook a detailed characterization of the proportions of the different B cell subsets in 33 patients with CFS fulfilling the Canadian and Fukada criteria for CFS and compared these with 24 age- and gender-matched healthy controls (HC). CFS patients had greater numbers of naive B cells as a percentage of lymphocytes: 6·3 versus 3·9% in HC (P = 0·034), greater numbers of naive B cells as a percentage of B cells: 65 versus 47% in controls (P = 0·003), greater numbers of transitional B cells: 1·8 versus 0·8% in controls (P = 0·025) and reduced numbers of plasmablasts: 0·5 versus 0·9% in controls (P = 0·013). While the cause of these changes is unclear, we speculate whether they may suggest a subtle tendency to autoimmunity.

Figure 1

B cell gating strategy. The first gate, R1, selects lymphocytes based on side-scatter versus forward-scatter. These cells are analysed further for CD19 expression and the second gate, R2, selects B cells (CD19⁺ cells). These B cells (R6) are analysed further to determine proportions of non-switched memory, class-switched memory, marginal zone and naive B cells.

Figure 2

B cell gating strategy for determining CD38^lowCD21^low, transitional B cells (CD38^hiIgM^hi) and plasmablast (CD38^hiIgM^low) subpopulations. The first gate, R5, selects lymphocytes based on side-scatter versus forward-scatter. CD19 expression is used to select B cells (CD19⁺ cells) in the second gate, R6. The B cells (R6) are analysed further for CD21 and CD38 expression to identify gate 7, CD38^lowCD21^low cells. Alternatively, the B cells (R6) are analysed for immunoglobulin (Ig)M versus CD38 expression to identify gate 8, transitional B cells (CD38^hiIgM^hi) and gate 9, plasmablasts (CD38^hiIgM^low).

Figure 3

Graphs summarizing B cell subsets which are significantly different between 33 chronic fatigue syndrome (CFS) patients and 24 donors. (a) Percentage of B cells that are transitional B cells. CFS patients had 1·8 versus 0·8% in healthy controls (P = 0·025). (b) Percentage of lymphocytes that are naive B cells. CFS patients had 6·3 versus 3·9% in healthy controls (P = 0·034). (c) Percentage of B cells that are naive B cells. CFS patients had 65 versus 47% in controls (P = 0·003). (d) Percentage of B cells that are plasmablasts. CFS patients had 0·5 versus 0·9% in controls (P = 0·013).