CXCR4 and lymphopenia: Limited information exists on the migratory behavior of T cell subpopulations during sepsis: CXCR4, the receptor for CXCL12, is expressed on naïve and memory T-cell subsets early during sepsis, and the pharmacological inhibition of CXCR4 prevents lymphopenia in the spleen, whereas it increases the number of T cells in the blood (40).