Autophagy links antimicrobial activity with antigen presentation in Langerhans cells
Angeline Tilly Dang, Rosane M.B. Teles, Phillip T. Liu, Aaron Choi, Annalisa Legaspi, Euzenir N. Sarno, Maria T. Ochoa, Kislay Parvatiyar, Genhong Cheng, Michel Gilliet, Barry R. Bloom, Robert L. Modlin
Angeline Tilly Dang, Rosane M.B. Teles, Phillip T. Liu, Aaron Choi, Annalisa Legaspi, Euzenir N. Sarno, Maria T. Ochoa, Kislay Parvatiyar, Genhong Cheng, Michel Gilliet, Barry R. Bloom, Robert L. Modlin
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Research Article Immunology Infectious disease

Autophagy links antimicrobial activity with antigen presentation in Langerhans cells

Abstract

DC, through the uptake, processing, and presentation of antigen, are responsible for activation of T cell responses to defend the host against infection, yet it is not known if they can directly kill invading bacteria. Here, we studied in human leprosy, how Langerhans cells (LC), specialized DC, contribute to host defense against bacterial infection. IFN-γ treatment of LC isolated from human epidermis and infected with Mycobacterium leprae (M. leprae) activated an antimicrobial activity, which was dependent on the upregulation of the antimicrobial peptide cathelicidin and induction of autophagy. IFN-γ induction of autophagy promoted fusion of phagosomes containing M. leprae with lysosomes and the delivery of cathelicidin to the intracellular compartment containing the pathogen. Autophagy enhanced the ability of M. leprae–infected LC to present antigen to CD1a-restricted T cells. The frequency of IFN-γ labeling and LC containing both cathelicidin and autophagic vesicles was greater in the self-healing lesions vs. progressive lesions, thus correlating with the effectiveness of host defense against the pathogen. These data indicate that autophagy links the ability of DC to kill and degrade an invading pathogen, ensuring cell survival from the infection while facilitating presentation of microbial antigens to resident T cells.

Authors

Angeline Tilly Dang, Rosane M.B. Teles, Phillip T. Liu, Aaron Choi, Annalisa Legaspi, Euzenir N. Sarno, Maria T. Ochoa, Kislay Parvatiyar, Genhong Cheng, Michel Gilliet, Barry R. Bloom, Robert L. Modlin

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Figure 3

Cathelicidin is involved in antimicrobial activity.

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Cathelicidin is involved in antimicrobial activity. Human LCDC were stim...
Human LCDC were stimulated with rIFN-γ in 10% vitamin D–sufficient human serum. Cathelicidin and DEFB4 gene expression was assessed by qPCR. (A) LCDC data are represented as mean fold change ± SEM, n = 8. (B) Human primary CD1a+ LC data are represented as mean fold change ± SEM, n = 7. (C) Human LCDC were stimulated with rIFN-γ, fixed, and immunolabeled with anti-cathelicidin antibody (green) and anti-CD1a antibody (red). Representative shown of 4 independent experiments. (D) The percentage of cathelicidin+ cells was determined. Data are represented as mean ± SEM, n = 4. (E) Human LCDC were stimulated with rIFN-γ for 4 hours, washed and infected with PKH26-M. leprae (red) at a MOI of 10 overnight, and washed and stimulated with rIFN-γ for an additional 4 hours. Infected cells were fixed and immunolabeled with anti-cathelicidin antibody (green) and anti-LAMP1 antibody (cyan). Nuclei were stained with DAPI (blue). Overlay of PKH26–M. leprae and cathelicidin, without LAMP1, shown in boxed inset. Representative shown of 4 independent experiments. (F and G) Human LCDC were transfected with siRNA oligos specific for cathelicidin (siCath) or nonspecific (siCTRL) and then treated with rIFN-γ in 10% human vitamin D–sufficient serum for 4 hours, washed and infected with M. leprae overnight, and washed and transfected with siRNA oligos and rIFN-γ for an additional 4 days. (F) Viability of M. leprae was calculated, and percent increase or decrease relative to no treatment (media) was determined. Data are represented as mean ± SEM, n = 4. (G) Following overnight infection with PKH26-M. leprae (red) overnight, LCDC were washed and stimulated with siRNA oligos and rIFN-γ for an additional 4 hours and immunolabeled with anti-cathelicidin antibody (green) and anti-LAMP1 antibody (cyan). Representative shown of 3 independent experiments. (C, E, and G) Images captured on a 63× lens, with 6× zoom. *P < 0.05, **P < 0.01. Two-tailed Student’s t test (A, B, and D) or repeated measures 1-way ANOVA (F).