Correlation of Peripheral Immunity With Rapid Amyotrophic Lateral Sclerosis Progression

Abstract

Importance: Amyotrophic lateral sclerosis (ALS) has an immune component, but previous human studies have not examined immune changes over time.

Objectives: To assess peripheral inflammatory markers in participants with ALS and healthy control individuals and to track immune changes in ALS and determine whether these changes correlate with disease progression.

Design, setting, and participants: In this longitudinal cohort study, leukocytes were isolated from peripheral blood samples from 35 controls and 119 participants with ALS at the ALS Clinic of the University of Michigan, Ann Arbor, from June 18, 2014, through May 26, 2016. Follow-up visits occurred every 6 to 12 months. Fifty-one participants with ALS provided samples at multiple points. Immune cell populations were measured and compared between control and ALS groups. Surface marker expression of CD11b+ myeloid cells was also assessed. Changes over time were correlated with disease progression using multivariate regression.

Main outcomes and measures: The number of immune cells per milliliter of blood and the fold expression of cell surface markers. Multivariate regression models were used to correlate changes in immune metrics with changes on the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R).

Results: Thirty-five controls (17 women [48.6%] and 18 men [51.4%]; mean [SD] age, 63.5 [9.9] years) and 119 participants with ALS (50 women [42.0%] and 69 men [68.0%]; mean [SD] age, 61.4 [11.5] years) were enrolled. Compared with controls, participants with ALS had increased mean (SEM) counts ( × 106/mL) of total leukocytes (4.57 [0.29; 95% CI, 3.94-5.11] vs 5.53 [0.16; 95% CI, 5.21-5.84]), neutrophils (2.87 [0.23; 95% CI, 2.40-3.35] vs 3.80 [0.12; 95% CI, 3.56-4.04]), CD16+ monocytes (0.03 [0.003; 95% CI, 0.02-0.04] vs 0.04 [0.002; 95% CI, 0.03-0.04]), CD16- monocytes (0.25 [0.02; 95% CI, 0.21-0.30] vs 0.29 [0.01; 95% CI, 0.27-0.31]), and natural killer cells (0.13 [0.02; 95% CI, 0.10-0.17] vs 0.18 [0.01; 95% CI, 0.16-0.21]). We also observed an acute, transient increase in a population of CD11b+ myeloid cells expressing HLA-DR, CD11c, and CX3CR1. Finally, early changes in immune cell numbers had a significant correlation with disease progression measured by change in ALSFRS-R score, particularly neutrophils (-4.37 [95% CI, -6.60 to -2.14] per 11.47 × 104/mL [SD, 58.04 × 104/mL] per year) and CD4 T cells (-30.47 [95% CI, -46.02 to -14.94] per -3.72 × 104/mL [SD, 26.21 × 104/mL] per year).

Conclusions and relevance: Changes in the immune system occur during ALS and may contribute to the pathologic features of ALS.

Figure 1.. Total Number of Peripheral Immune Cells in Participants With Amyotrophic Lateral Sclerosis (ALS)

The total number of leukocytes and numbers of individual cell populations were calculated for each participant with ALS by calculating the mean population numbers at each visit to create a single value per patient. Cell populations in participants with ALS were compared with those of healthy control participants. Horizontal lines indicate mean; error bars, SEM for each cell population. NK indicates natural killer. ^aP < .001, Mann-Whitney test; ^bP < .01, Mann-Whitney test; ^cP < .05, Mann-Whitney test.

Figure 2.. Total Number and Changes in CD11b⁺CD14⁻CD16⁻ Cell Subpopulations in Participants With Amyotropic Lateral Sclerosis (ALS)

Total numbers of cells in CD11b⁺CD14⁻CD16⁻ cell subpopulations for each participant with ALS were calculated using the mean population numbers at each visit to create 1 value per patient (left). Horizontal lines indicate mean; error bars, SEM for each population. Time from ALS onset (middle) and the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) score (range, 0-48; lower scores indicate more advanced disease) (right) for participants with ALS were calculated for each visit and plotted vs subpopulation number for multiple visits. Lines are for reference and do not indicate change over time because controls did not make multiple clinic visits. Participants with ALS with 1 clinic visit are not included in the kinetic data. ^aP < .05, Mann-Whitney test.