Ly6G deficiency alters the dynamics of neutrophil recruitment and pathogen capture during Leishmania major skin infection

Abstract

Neutrophils represent one of the first immune cell types recruited to sites of infection, where they can control pathogens by phagocytosis and cytotoxic mechanisms. Intracellular pathogens such as Leishmania major can hijack neutrophils to establish an efficient infection. However the dynamic interactions of neutrophils with the pathogen and other cells at the site of the infection are incompletely understood. Here, we have investigated the role of Ly6G, a homolog of the human CD177 protein, which has been shown to interact with cell adhesion molecules, and serves as a bona fide marker for neutrophils in mice. We show that Ly6G deficiency decreases the initial infection rate of neutrophils recruited to the site of infection. Although the uptake of L. major by subsequently recruited monocytes was tightly linked with the concomitant uptake of neutrophil material, this process was not altered by Ly6G deficiency of the neutrophils. Instead, we observed by intravital 2-photon microscopy that Ly6G-deficient neutrophils entered the site of infection with delayed initial recruitment kinetics. Thus, we conclude that by promoting neutrophils’ ability to efficiently enter the site of infection, Ly6G contributes to the early engagement of intracellular pathogens by the immune system.

Quantitative single-cell analysis of Leishmania major amastigote differentiation demonstrates variably extended expression of the lipophosphoglycan (LPG) virulence factor in different host cell types

“…How this transfer of the parasite from the first cell type infected to macrophages occurs is an area of intense study; parasites could be released from the infected cell and subsequently taken up [7] and/or the infected cell itself is engulfed [8,12,23,50], with both routes seeming likely to transfer LPG-retaining parasites. In the future it would be interesting to extend the quantitative single cell approaches developed here to the question of LPG retention in other cell types (neutrophils, inflammatory monocytes, tissue resident macrophages, keratinocytes or other cell types known to harbor Leishmania during establishment [6][7][8][9][10][11]) in vitro or in vivo.…”

“…Moreover, parasites can 'transit' from one cell type to another, for example from neutrophils to DCs or macrophages [6][7][8]11]. These cell-to-cell transitions likely happen within 1-2 days after infection, since the majority of parasites are found within macrophages after this period [7,8,12,13].…”

Quantitative single-cell analysis of Leishmania major amastigote differentiation demonstrates variably extended expression of the lipophosphoglycan (LPG) virulence factor in different host cell types

“…How this transfer of the parasite from the first cell type infected to macrophages occurs is an area of intense study; parasites could be released from the infected cell and subsequently taken up [10] and/or the infected cell itself is engulfed [11, 15, 26, 46], with both routes seeming likely to transfer LPG-retaining parasites. Testing the role of LPG in these widely varying settings will require the application of technologies in which parasite glycoconjugate expression can be manipulated over a short time frame, while the parasite is within the phagolysosome or in transit [47].…”

“…Moreover, parasites can 'transit' from one cell type to another, for example from neutrophils to DCs or macrophages [9][10][11]14]. These cell-tocell transitions likely happen within 1-2 days after infection, since the majority of parasites are found within macrophages after this period [10,11,15,16]. Different cell types encountered by invading Leishmania metacyclics likely present different challenges, reflecting variation in the intracellular environment and innate immune responses.…”

Lymphocyte antigen 6 complex locus G6D downregulation is a novel parameter for functional impairment of neutrophils in aged mice

“…Furthermore, the ligation of Ly-6G by using monoclonal antibody (mAb, 1A8) suppressed the migration ( 15 ). Another report showed that Ly-6G deficiency critically impaired the early recruitment of neutrophils in an Leishmania major -infected site ( 16 ). In this report, the role of Ly-6G in the differentiation step was also discussed.…”