Heat-killed Lactobacillus acidophilus La205 enhances NK cell cytotoxicity through increased granule exocytosis

Soyoung Cheon, Ki Woong Lee, Kyung Eun Kim, Jung Kyu Park, Sunyoung Park, Chul hyun Kim, Daejin Kim, Hyong Joo Lee, Daeho Cho

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18 Citations (Scopus)


Heat-killed lactic acid bacteria (LAB) are known to be important immunomodulators that stimulate tumor necrosis factor-α (TNF-α) and nitric oxide (NO) production as well as increase phagocytic activity in macrophages. NK cells play a critical role in innate immune response and induce spontaneous killing of tumor cells and virus-infected cells. However, the effect of heat-killed LAB on NK cells is still unclear. In this study, we investigated the effect of heat-killed Lactobacillus acidophilus La205 (La205) on NK cytolytic activity. We found that heat-killed La205 directly stimulated NK cytolytic activity in dose- and time-dependent manners. To determine the mechanism underlying heat-killed La205-enhanced NK cytotoxicity, the expression of NK activating receptors was tested. Heat-killed La205 did not affect the expression of NK activating receptors. To investigate whether NK degranulation is related to heat-killed La205-enhanced NK cytotoxicity, NK degranulation inhibitor concanamycin A (CMA) was used. CMA effectively blocked heat-killed La205-induced NK cytotoxicity, and an assay for detection of a degranulation marker, CD107a, showed that heat-killed La205 increased granule exocytosis approximately 2-fold in comparison to non-treated NK cells. In addition, heat-killed La205 dramatically elevated mRNA expression of granulysin, a component of the cytolytic granule contents, in NK cells. However, other granule contents, including perforin and granzymes, were not changed by heat-killed La205. From these data, we concluded that heat-killed La205 stimulated NK cytolytic activity through enhancement of granule exocytosis, and granulysin may be a critical mediator in heat-killed La205-induced granule exocytosis.

Original languageEnglish
Pages (from-to)171-176
Number of pages6
JournalImmunology Letters
Issue number2
Publication statusPublished - 2011 May
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by the Sookmyung Women's University Research Grants 2008.


  • Cytotoxicity
  • Granule exocytosis
  • Granulysin
  • Lactic acid bacteria (LAB)
  • Lactobacillus acidophilus La205 (La205)
  • NK cell

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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