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Sustained Immune Complex-Mediated Reduction in CD16 Expression after Vaccination Regulates NK Cell Function

View Article: PubMed Central - PubMed

ABSTRACT

Cross-linking of FcγRIII (CD16) by immune complexes induces antibody-dependent cellular cytotoxicity (ADCC) by natural killer (NK) cells, contributing to control of intracellular pathogens; this pathway can also be targeted for immunotherapy of cancerous or otherwise diseased cells. However, downregulation of CD16 expression on activated NK cells may limit or regulate this response. Here, we report sustained downregulation of CD16 expression on NK cells in vivo after intramuscular (but not intranasal) influenza vaccination. CD16 downregulation persisted for at least 12 weeks after vaccination and was associated with robust enhancement of influenza-specific plasma antibodies after intramuscular (but not intranasal) vaccination. This effect could be emulated in vitro by co-culture of NK cells with influenza antigen and immune serum and, consistent with the sustained effects after vaccination, only very limited recovery of CD16 expression was observed during long-term in vitro culture of immune complex-treated cells. CD16 downregulation was most marked among normally CD16high CD57+ NK cells, irrespective of NKG2C expression, and was strongly positively associated with degranulation (surface CD107a expression). CD16 downregulation was partially reversed by inhibition of ADAM17 matrix metalloprotease, leading to a sustained increase in both CD107a and CD25 (IL-2Rα) expression. Both the degranulation and CD25 responses of CD57+ NK cells were uniquely dependent on trivalent influenza vaccine-specific IgG. These data support a role for CD16 in early activation of NK cells after vaccination and for CD16 downregulation as a means to modulate NK cell responses and maintain immune homeostasis of both antibody and T cell-dependent pathways.

No MeSH data available.


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Shedding of CD16 is mediated by ADAM17. PBMCs were cultured for 6 h with TIV and FCS or immune AB plasma (AB) in the presence or absence of the MMP inhibitor TAP1-1 (A,B) or the D1(A12) blocking antibody to ADAM17 (C,D) and the relevant negative controls (DMSO and mIgG1, respectively). CD16 (MFI) (A,C) and CD107a (%) (B,D) were assessed by flow cytometry on CD56dim, CD56dimCD57− and CD56dimCD57+ NK cells. Data are presented for 10 different individuals. Paired comparisons between conditions were made using Mann–Whitney U test. *p < 0.05, **p < 0.01, ***p < 0.001.
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Figure 4: Shedding of CD16 is mediated by ADAM17. PBMCs were cultured for 6 h with TIV and FCS or immune AB plasma (AB) in the presence or absence of the MMP inhibitor TAP1-1 (A,B) or the D1(A12) blocking antibody to ADAM17 (C,D) and the relevant negative controls (DMSO and mIgG1, respectively). CD16 (MFI) (A,C) and CD107a (%) (B,D) were assessed by flow cytometry on CD56dim, CD56dimCD57− and CD56dimCD57+ NK cells. Data are presented for 10 different individuals. Paired comparisons between conditions were made using Mann–Whitney U test. *p < 0.05, **p < 0.01, ***p < 0.001.

Mentions: CD16 shedding was significantly reduced on both CD57− and CD57+ NK cells when they were incubated with TIV and immune plasma in the presence of the ADAM17 inhibitor, TAPI-1 (Figure 4A) but not when incubated with the DMSO vehicle control. Notably, TAPI-1-mediated maintenance of CD16 expression was associated with enhanced degranulation as indicated by a significant increase in the frequency of CD107a+ cells, particularly within the highly cytotoxic CD56dimCD57+ subset (Figure 4B). While there is a modest trend toward an increase in CD16 MFI when NK cells are cultured with FCS in the presence of TAPI-1, this is not statistically significant and there is no effect on degranulation. Moreover, blocking the active site of ADAM17 with a specific monoclonal antibody also prevented IgG–TIV-mediated shedding of CD16 (Figure 4C) and enhanced CD107a expression, although to a somewhat lesser extent than the TAPI-1 inhibitor (Figure 4D); these effects were not observed when cells were cultured in FCS rather than immune human serum. However, although specific monoclonal antibody blockade of ADAM17 was sufficient to prevent CD16 shedding, the more effective enhancement of degranulation by the TAPI-1 inhibitor suggests that this may additionally target other molecules involved in the discharge or recycling of cytotoxic granules.


Sustained Immune Complex-Mediated Reduction in CD16 Expression after Vaccination Regulates NK Cell Function
Shedding of CD16 is mediated by ADAM17. PBMCs were cultured for 6 h with TIV and FCS or immune AB plasma (AB) in the presence or absence of the MMP inhibitor TAP1-1 (A,B) or the D1(A12) blocking antibody to ADAM17 (C,D) and the relevant negative controls (DMSO and mIgG1, respectively). CD16 (MFI) (A,C) and CD107a (%) (B,D) were assessed by flow cytometry on CD56dim, CD56dimCD57− and CD56dimCD57+ NK cells. Data are presented for 10 different individuals. Paired comparisons between conditions were made using Mann–Whitney U test. *p < 0.05, **p < 0.01, ***p < 0.001.
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Figure 4: Shedding of CD16 is mediated by ADAM17. PBMCs were cultured for 6 h with TIV and FCS or immune AB plasma (AB) in the presence or absence of the MMP inhibitor TAP1-1 (A,B) or the D1(A12) blocking antibody to ADAM17 (C,D) and the relevant negative controls (DMSO and mIgG1, respectively). CD16 (MFI) (A,C) and CD107a (%) (B,D) were assessed by flow cytometry on CD56dim, CD56dimCD57− and CD56dimCD57+ NK cells. Data are presented for 10 different individuals. Paired comparisons between conditions were made using Mann–Whitney U test. *p < 0.05, **p < 0.01, ***p < 0.001.
Mentions: CD16 shedding was significantly reduced on both CD57− and CD57+ NK cells when they were incubated with TIV and immune plasma in the presence of the ADAM17 inhibitor, TAPI-1 (Figure 4A) but not when incubated with the DMSO vehicle control. Notably, TAPI-1-mediated maintenance of CD16 expression was associated with enhanced degranulation as indicated by a significant increase in the frequency of CD107a+ cells, particularly within the highly cytotoxic CD56dimCD57+ subset (Figure 4B). While there is a modest trend toward an increase in CD16 MFI when NK cells are cultured with FCS in the presence of TAPI-1, this is not statistically significant and there is no effect on degranulation. Moreover, blocking the active site of ADAM17 with a specific monoclonal antibody also prevented IgG–TIV-mediated shedding of CD16 (Figure 4C) and enhanced CD107a expression, although to a somewhat lesser extent than the TAPI-1 inhibitor (Figure 4D); these effects were not observed when cells were cultured in FCS rather than immune human serum. However, although specific monoclonal antibody blockade of ADAM17 was sufficient to prevent CD16 shedding, the more effective enhancement of degranulation by the TAPI-1 inhibitor suggests that this may additionally target other molecules involved in the discharge or recycling of cytotoxic granules.

View Article: PubMed Central - PubMed

ABSTRACT

Cross-linking of Fc&gamma;RIII (CD16) by immune complexes induces antibody-dependent cellular cytotoxicity (ADCC) by natural killer (NK) cells, contributing to control of intracellular pathogens; this pathway can also be targeted for immunotherapy of cancerous or otherwise diseased cells. However, downregulation of CD16 expression on activated NK cells may limit or regulate this response. Here, we report sustained downregulation of CD16 expression on NK cells in vivo after intramuscular (but not intranasal) influenza vaccination. CD16 downregulation persisted for at least 12&thinsp;weeks after vaccination and was associated with robust enhancement of influenza-specific plasma antibodies after intramuscular (but not intranasal) vaccination. This effect could be emulated in vitro by co-culture of NK cells with influenza antigen and immune serum and, consistent with the sustained effects after vaccination, only very limited recovery of CD16 expression was observed during long-term in vitro culture of immune complex-treated cells. CD16 downregulation was most marked among normally CD16high CD57+ NK cells, irrespective of NKG2C expression, and was strongly positively associated with degranulation (surface CD107a expression). CD16 downregulation was partially reversed by inhibition of ADAM17 matrix metalloprotease, leading to a sustained increase in both CD107a and CD25 (IL-2R&alpha;) expression. Both the degranulation and CD25 responses of CD57+ NK cells were uniquely dependent on trivalent influenza vaccine-specific IgG. These data support a role for CD16 in early activation of NK cells after vaccination and for CD16 downregulation as a means to modulate NK cell responses and maintain immune homeostasis of both antibody and T cell-dependent pathways.

No MeSH data available.


Related in: MedlinePlus