Investigating Innate Tolerization of Myeloid Cells to Mycobacterium tuberculosis Glycolipids
(2022) MOBN03 20222Degree Projects in Molecular Biology
- Abstract
- Tuberculosis (TB), caused by infection with Mycobacterium tuberculosis (Mtb) remains a global health threat, claiming 1.6 million lives in 2021 alone and infecting an estimated quarter of the world’s population in a latent or controlled infection. Glycolipids make up a large part of the bacterial cell wall and closely interact with innate immune cells, influencing their response upon infection. Therefore, to better understand resistance and control mechanisms in TB, we need to investigate the innate immune response to mycobacterial glycolipids. Lipoarabinomannan (LAM) and phosphatidyl-myo-inositol mannoside (PIM) are major glycolipid components of the Mtb cell wall and have exhibited immunomodulatory properties of the host’s innate immune... (More)
- Tuberculosis (TB), caused by infection with Mycobacterium tuberculosis (Mtb) remains a global health threat, claiming 1.6 million lives in 2021 alone and infecting an estimated quarter of the world’s population in a latent or controlled infection. Glycolipids make up a large part of the bacterial cell wall and closely interact with innate immune cells, influencing their response upon infection. Therefore, to better understand resistance and control mechanisms in TB, we need to investigate the innate immune response to mycobacterial glycolipids. Lipoarabinomannan (LAM) and phosphatidyl-myo-inositol mannoside (PIM) are major glycolipid components of the Mtb cell wall and have exhibited immunomodulatory properties of the host’s innate immune cells. Among observed effects was a dampened cytokine production among myeloid cells in patients with latent TB compared to healthy controls. This suggests that monocytes could be tolerized in TB infection, perhaps contributing to evasion of active TB disease. In this project, we investigated innate tolerization mechanisms by stimulating monocytes and monocyte-derived macrophages (MDMs) with Mtb glycolipids. We were able to demonstrate induced tolerization of monocytes and MDMs to PIM whereas stimulations with LAM and Mtb lysate gave varied results. Blockade of TLR2 prior to glycolipid stimulation indicated a significant but not complete reliance on TLR2 as a receptor for tolerization in PIM and we demonstrated PIM’s ability to tolerize was dependent upon stimulation concentration. This study will later be supplemented with ATAC-seq of tolerized cells to gain a better understanding of how the epigenome is influenced by Mtb glycolipid-induced tolerization. (Less)
- Popular Abstract
- Tuberculosis Glycolipids Program Tolerization in Innate Immunity
Tuberculosis (TB) remains a public health emergency, with unknown mechanisms by which hosts enter different disease outcomes (symptomatic or asymptomatic) making it difficult to eradicate. Lipoarabinomannan (LAM) and phosphatidyl-myo-inositol mannoside (PIM) are major glycolipid components of the Mycobacterium tuberculosis (Mtb) cell wall and have exhibited immunomodulatory properties on the host’s innate immune cells such as a dampened cytokine production among myeloid cells in patients with latent TB compared to healthy controls. This suggests that monocytes develop tolerizing memory due to Mtb stimulation. This tolerization could contribute to the ability of individuals... (More) - Tuberculosis Glycolipids Program Tolerization in Innate Immunity
Tuberculosis (TB) remains a public health emergency, with unknown mechanisms by which hosts enter different disease outcomes (symptomatic or asymptomatic) making it difficult to eradicate. Lipoarabinomannan (LAM) and phosphatidyl-myo-inositol mannoside (PIM) are major glycolipid components of the Mycobacterium tuberculosis (Mtb) cell wall and have exhibited immunomodulatory properties on the host’s innate immune cells such as a dampened cytokine production among myeloid cells in patients with latent TB compared to healthy controls. This suggests that monocytes develop tolerizing memory due to Mtb stimulation. This tolerization could contribute to the ability of individuals to control infection in a latent asymptomatic state instead of progressing to active infection. In this project, we investigated innate tolerization mechanisms in myeloid cells by stimulating monocytes and monocyte-derived macrophages (MDMs) with Mtb glycolipids.
PIM Stimulation Results in Downregulated Cytokine Response Upon Secondary Stimulation
We isolated and differentiated monocytes into M1 and M2-like monocyte-derived macrophages (MDMs). We then stimulated monocytes and MDMs with mycobacterial glycolipids PIM and LAM for 24 hours. After stimulation, cells were washed and rested for five days before being rechallenged with Lipopolysaccharide (LPS). We noted a significantly diminished TNF-α secretion in all cell types in conditions stimulated with PIM, indicating its ability to tolerize cells. The same effect was observed in monocytes that were stimulated with LAM and Mtb lysate.
Conclusion
In this project, we stimulated pure monocytes with two major glycolipids of the mycobacterial cell envelope: PIM and LAM. We successfully demonstrated the ability of PIM to modulate cytokine response in monocytes, M1, an M2-like monocyte derived macrophages. We also further demonstrated the at least partial dependance of TLR2 in PIM’s downregulation of cytokine secretion in monocytes. We did not observe consistent immunomodulatory effects from LAM. We concluded this study by displaying the direct correlation of increasing PIM stimulation concentration with decreased cytokine secretion. Our studies have solidified PIM’s role as an immunomodulatory agent during TB infection and may help inform us how Mtb can induce a controlled or latent infection as opposed to immediate progression into active disease.
Master’s Degree Project in Molecular Biology MOBN03, 60 credits
Department of Biology, Lund University
Advisor: Christopher Sundling, christopher.sundling@ki.se
Karolinska Institute Department of Medicine, Solna (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9140723
- author
- Gower, Maia Serene
- supervisor
- organization
- course
- MOBN03 20222
- year
- 2022
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9140723
- date added to LUP
- 2023-11-01 11:03:16
- date last changed
- 2023-11-01 11:03:16
@misc{9140723,
abstract = {{Tuberculosis (TB), caused by infection with Mycobacterium tuberculosis (Mtb) remains a global health threat, claiming 1.6 million lives in 2021 alone and infecting an estimated quarter of the world’s population in a latent or controlled infection. Glycolipids make up a large part of the bacterial cell wall and closely interact with innate immune cells, influencing their response upon infection. Therefore, to better understand resistance and control mechanisms in TB, we need to investigate the innate immune response to mycobacterial glycolipids. Lipoarabinomannan (LAM) and phosphatidyl-myo-inositol mannoside (PIM) are major glycolipid components of the Mtb cell wall and have exhibited immunomodulatory properties of the host’s innate immune cells. Among observed effects was a dampened cytokine production among myeloid cells in patients with latent TB compared to healthy controls. This suggests that monocytes could be tolerized in TB infection, perhaps contributing to evasion of active TB disease. In this project, we investigated innate tolerization mechanisms by stimulating monocytes and monocyte-derived macrophages (MDMs) with Mtb glycolipids. We were able to demonstrate induced tolerization of monocytes and MDMs to PIM whereas stimulations with LAM and Mtb lysate gave varied results. Blockade of TLR2 prior to glycolipid stimulation indicated a significant but not complete reliance on TLR2 as a receptor for tolerization in PIM and we demonstrated PIM’s ability to tolerize was dependent upon stimulation concentration. This study will later be supplemented with ATAC-seq of tolerized cells to gain a better understanding of how the epigenome is influenced by Mtb glycolipid-induced tolerization.}},
author = {{Gower, Maia Serene}},
language = {{eng}},
note = {{Student Paper}},
title = {{Investigating Innate Tolerization of Myeloid Cells to Mycobacterium tuberculosis Glycolipids}},
year = {{2022}},
}