CD19 and myeloid sarcoma: To evaluate the activation status of immune cells both at basal level and after stimulation, we exposed lympho-monocytes from MS patients and controls to a pool of SARS-CoV-2 spike peptides (Peptivator) and assessed four activation cell surface markers (CD69, HLA-DR, CD25, and CD137) in helper (CD4+), cytotoxic (CD8+) and B (CD19+) lymphocytes.