Chemokine Receptor Expression on Normal Blood CD56+ NK-Cells Elucidates Cell Partners That Comigrate during the Innate and Adaptive Immune Responses and Identifies a Transitional NK-Cell Population

Abstract

Studies of chemokine receptors (CKR) in natural killer- (NK-) cells have already been published, but only a few gave detailed information on its differential expression on blood NK-cell subsets. We report on the expression of the inflammatory and homeostatic CKR on normal blood CD56 + low CD16+ and CD56 + high CD16 - / + low NK-cells. Conventional CD56 + low and CD56 + high NK-cells present in the normal PB do express CKR for inflammatory cytokines, although with different patterns CD56 + low NK-cells are mainly CXCR1/CXCR2+ and CXCR3/CCR5-/+, whereas mostly CD56 + high NK-cells are CXCR1/CXCR2- and CXCR3/CCR5+. Both NK-cell subsets have variable CXCR4 expression and are CCR4- and CCR6-. The CKR repertoire of the CD56 + low NK-cells approaches to that of neutrophils, whereas the CKR repertoire of the CD56 + high NK-cells mimics that of Th1+ T cells, suggesting that these cells are prepared to migrate into inflamed tissues at different phases of the immune response. In addition, we describe a subpopulation of NK-cells with intermediate levels of CD56 expression, which we named CD56 + int NK-cells. These NK-cells are CXCR3/CCR5+, they have intermediate levels of expression of CD16, CD62L, CD94, and CD122, and they are CD57- and CD158a-. In view of their phenotypic features, we hypothesize that they correspond to a transitional stage, between the well-known CD56 + high and CD56 + low NK-cells populations.