Article

Natural killer cells: Walking three paths down memory lane

University of California, San Francisco, San Francisco, California, United States
Trends in Immunology (Impact Factor: 10.4). 03/2013; 34(6). DOI: 10.1016/j.it.2013.02.005
Source: PubMed

ABSTRACT

Immunological memory has traditionally been regarded as a unique feature of the adaptive immune response, mediated in an antigen-specific manner by T and B lymphocytes. All other hematopoietic cells, including natural killer (NK) cells, are classified as innate immune cells, which have been considered short-lived but can respond rapidly against pathogens in a manner not thought to be driven by antigen. Interestingly, NK cells have recently been shown to survive long term after antigen exposure and subsequently mediate antigen-specific recall responses. In this review, we address the similarities between, and the controversies surrounding, three major viewpoints of NK memory that have arisen from these recent studies: (i) mouse cytomegalovirus (MCMV)-induced memory; (ii) cytokine-induced memory; and (iii) liver-restricted memory cells.

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Available from: Yosuke Kamimura, Jun 05, 2014
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    • "In regards to the latter, NK cells have been described as having some aspects of memory, with changed phenotype lasting long after exposure to infection [35] [36]. In addition to detectible receptor expression, NK cells were shown here to respond to the TLR1/2 agonist, Pam3sk4, and this induced activity correlated with hBD-3 induced activity (Fig. 6B). "
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    • "Accumulating evidence now support that NK cells possess properties previously attributed to the adaptive immune system. Long-lived NK cells differentiate following viral infection; they exhibit functions that recall those of memory lymphocytes(reviewed in [159]. DNAM-1 was recently shown to play a critical role in the generation of memory NK cells following MCMV infection[160]. "
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    • "Prior studies have established that NK cells can mount an immune response with many of the features of adaptive immunity when challenged with viruses or chemical haptens (O'Leary et al., 2006; Sun et al., 2009a, 2010; Paust et al., 2010; Min-Oo et al., 2013). Here, we have examined whether alloantigens also elicit the expansion of alloantigen-specific NK cells with enhanced responses upon rechallenge. "
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    ABSTRACT: Natural killer (NK) cells provide important host defense against microbial pathogens and can generate a population of long-lived memory NK cells after infection or immunization. Here, we addressed whether NK cells can expand and differentiate after alloantigen stimulation, which may be important in hematopoietic stem cell and solid tissue transplantation. A subset of NK cell in C57BL/6 mice expresses the activating Ly49D receptor that is specific for H-2D(d). These Ly49D(+) NK cells can preferentially expand and differentiate when challenged with allogeneic H-2D(d) cells in the context of an inflammatory environment. H-2D(d) is also recognized by the inhibitory Ly49A receptor, which, when coexpressed on Ly49D(+) NK cells, suppresses the expansion of Ly49D(+) NK cells. Specificity of the secondary response of alloantigen-primed NK cells was defined by the expression of activating Ly49 receptors and regulated by the inhibitory receptors for MHC class I. Thus, the summation of signals through a repertoire of Ly49 receptors controls the adaptive immune features of NK cells responding to allogeneic cells.
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