CD4 and myeloid sarcoma: The scRNA-seq studies showed that CD8+TRM cells, CD4+TRM cells, and trNK cells existed in the cerebrospinal fluid of MS patients.423–425 CD8+T cells infiltrating in the recurrent MS lesions display tissue-resident phenotypes, contributing to the compartmentalized inflammation in the brain.426 Mechanistically, TRM cells interact with other immune cells to develop their tissue-resident characteristics in the CNS.