From the combination of the six intracellular biomarkers and CD137 for CD4+, CD8+, CD4+CD8+, and CD4−CD8−, the biomarkers that were detected to distinguish MISC_A from MISC_C, post-COVID-19, and controls are as follows: CD4+IL-17+, CD8+IL-17+, CD8+IFNγ+, CD4+GRB+, CD8+CD137+, CD4+IL-2+, and CD8+IL-2+. Here, CD8A is linked to COVID-19.