The total number of CD4+ and CD8+ T cells in the BM is not affected, but the size of CD4+ and CD8+ T cell subsets in the BM changes with age.5 Studies have shown that mesenchymal stromal cells in patients with multiple myeloma (B‐cell malignant tumors) exhibit aging characteristics: reduced phenotypic changes, differentiation and proliferation, and the production of higher levels of pro‐inflammatory cytokines. Here, CD4 is linked to plasma cell myeloma.