In the derivation cohort, CD3+T and CD4+T‐cell counts per 106/mL blood were both significantly decreased in ALS patients (0.29 × 106/mL [IQR: 0.15–0.41] vs. 0.47 × 106/mL [IQR: 0.26–0.56], p < 0.001, and 0.15 × 106/mL [IQR: 0.08–0.22] vs. 0.27 × 106/mL [IQR: 0.15–0.34], p < 0.001, respectively). Here, CD4 is linked to amyotrophic lateral sclerosis.