Reciprocal Activating Interaction between Natural Killer Cells and Dendritic Cells

We analyzed the interaction between human peripheral blood natural killer (NK) cells and monocyte-derived immature dendritic cells (DC). Fresh NK cells were activated, as indicated by the induced expression of the CD69 antigen, and their cytolytic activity was strongly augmented by contact with lipopolysaccharide (LPS)-treated mature DC, or with immature DC in the presence of the maturation stimuli LPS, Mycobacterium tuberculosis or interferon (IFN)-α. Reciprocally, fresh NK cells cultured with immature DC in the presence of the maturation stimuli strongly enhanced DC maturation and interleukin (IL)-12 production. IL-2–activated NK cells directly induced maturation of DC and enhanced their ability to stimulate allogeneic naive CD4+ T cells. The effects of NK cells were cell contact dependent, although the secretion of IFN-γ and TNF also contributed to DC maturation. Within peripheral blood lymphocytes the reciprocal activating interaction with DC was restricted to NK cells, because the other lymphocyte subsets were neither induced to express CD69, nor induced to mature in contact with DC. These data demonstrated for the first time a bidirectional cross talk between NK cells and DC, in which NK cells activated by IL-2 or by mature DC induce DC maturation

Increase of poly(ADP-ribose) polymerase mRNA levels during TPA-induced differentiation of human lymphocytes

AbstractThe non-mitogenic stimulation of human peripheral blood mononuclear cells (PBMC) with low concentrations of the phorbol ester 12-O-tetradecanoylphorbol 13-acatate (TPA) caused a progressive increase in the percent fraction of the cells that were positive for the early activating antigen CD69. At the same time, it caused a progressive increase in the steady-state levels of poly(ADP-ribose) polymerase (pADPRP) transcripts. A further increase in TPA concentration, while inducing the maximal expression of the levels of CD69 activating surface antigen, both in the presence or in the absence of proliferative activity, did not evoke any additional hightening of pADPRP mRNA levels. Time course of PBMC stimulation with a non-mitogenic dose or TPA showed an early increase in the accumulation of pADPRP mRNA, which changed at 8-16 h. and remained high for several days thereafter. On the basis of these data, we suggest flat the increase in pADPRP mRNA may be associated with the commitment of human lymphocytes from a quiescent (G0) to an activated (G1) state

Constitutive expression of CD69 in interspecies T-cell hybrids and locus assignment to human chromosome 12

In this study we describe the generation and characterization of interspecies somatic cell hybrids between human activated mature T cells and mouse BW5147 thymoma cells. A preferential segregation of human chromosomes was observed in the hybrids. Phenotypic analysis of two hybrids and their clones demonstrated coexpression of CD4 and CD69 antigens in the same cells. Segregation analysis of an informative family of hybrids followed by molecular and karyotype studies clearly demonstrated that the locus encoding CD69 antigen mapped to human chromosome 12. Although the expression of CD69 antigen is an early event after T-lymphocyte activation and rapidly declines in absence of exogenous stimuli, in the hybrids described in this study the expression was constitutive, similarly to what was previously found in early thymocyte precursors and mature thymocytes. In this respect it was important to note that the behavior of the hybrids in culture strongly suggested a dominant influence of the thymus-derived mouse tumor cell genome in controlling the constitutive expression of human CD69. These hybrids may thus provide a system to study the genetic and molecular mechanisms controlling the expression and function of this activation antigen

Interleukin-12 primes human CD4 and CD8 T cell clones for high production of both interferon-gamma and interleukin-10

Interleukin-12 (IL-12) induces differentiation of T helper 1 (Th1) cells, primarily through its ability to prime T cells for high interferon-gamma (IFN-gamma) production. We now report that the presence of IL-12 during the first several days of in vitro clonal expansion in limiting dilution cultures of polyclonally stimulated human peripheral blood CD4(+) and CD8(+) T cells also induces stable priming for high IL-10 production. This effect was demonstrated with T cells from both healthy donors and HIV(+) patients. Priming for IL-4 production, which requires IL-4, was maximum in cultures containing both IL-12 and IL-4. IL-4 modestly inhibited the IL-12-induced priming for IFN-gamma, but almost completely suppressed the priming for IL-10 production. A proportion of the clones generated from memory CD45RO(+) cells, but not those generated from naive CD45RO(-) CD4(+) T cells, produced some combinations of IFN-gamma, IL-10, and IL-4 even in the absence of IL-12 and IL-4, suggesting in vivo cytokine priming; virtually all CD4(+) clones generated from either CD45RO(-) or (+) cells, however, produced high levels of both IFN-gamma and IL-10 when IL-12 was present during expansion. These results indicate that each Th1-type (IFN-gamma) and Th2-type (IL-4 and IL-10) cytokine gene is independently regulated in human T cells and that the dichotomy between T cells with the cytokine production pattern of Th1 and Th2 cells is not due to a direct differentiation-inducing effect of immunoregulatory cytokines, but rather to secondary selective mechanisms. Particular combinations of cytokines induce a predominant generation of T cell clones with anomalous patterns of cytokine production (e.g., IFN-gamma and IL-4 or IFN-gamma and IL-10) that can also be found in a proportion of fresh peripheral blood T cells with ''memory'' phenotype or clones generated from them and that may identify novel Th subsets with immunoregulatory functions