<p>Murine Macrophage Requires CD11b to Recognize <em>Talaromyces marneffei</em></p>

Abstract

Introduction: Talaromyces marneffei (T. marneffei) is an emerging pathogenic fungus. Macrophage-1 antigen (Mac-1, CR3, CD11b/CD18) is an important receptor on innate immune cells and can recognize pathogens. However, the importance of CR3 in phagocytosis of T. marneffei by macrophages and their responses to T. marneffei have not been clarified. Methods: We show that interaction of mouse peritoneal macrophages (pMacs) or RAW264.7 macrophages with T. marneffei of its conidia spores and yeast cells enhances CR3 expression on macrophages. The phagocytosis rate was determined using flow cytometry, RT-PCR and Western blotting were used to detect CD11b expression, and the levels of IFN-γ, TNF-α, IL-2, IL-4, IL-6 and IL-10 in the co-culture supernatants were determined by ELISA. Results: Incubation of mouse macrophages with T. marneffei promoted phagocytosis of T. marneffei, which was dramatically mitigated by pretreatment with anti-CD11b antibody or knockdown of CR3 expression on macrophages. Then, interferon γ, tumor necrosis factor α, IL-4, IL-10 and IL-12 production in macrophages incubation with heat-killed T. marneffei was detected. CD11b expression on mouse macrophages was upregulated by T. marneffei. Incubation of T. marneffei promoted phagocytosis of T. marneffei by macrophages and high levels of pro-inflammatory and anti-inflammatory cytokine production by macrophages, which were mitigated and abrogated by pre-treatment with anti-CD11b or knockdown of CD11b expression. Conclusion: These data indicated that murine macrophage requires CD11b to recognize Talaromyces marneffei and their cytokine responses to heat-killed T. marneffei in vitro.

Identification of Oleanolic Acid as Allosteric Agonist of Integrin αM by Combination of In Silico Modeling and In Vitro Analysis

“…It pairs with integrin β 2 (CD18) to form the functional heterodimer α M β 2 (CD11b/CD18, Mac-1) that controls processes necessary for immune responses, such as actin skeleton reorganization, cell adhesion, phagocytosis, and cell migration. Accordingly, integrin α M β 2 is also important for pathogen removal and antigen presentation (Rosetti and Mayadas, 2016;Hu et al, 2020). In macrophages, specifically integrin α M negatively regulates proliferation and alternative macrophage polarization in obesity (Zheng et al, 2015), reduces the number of tumorinfiltrating immunosuppressive myeloid cells, and stimulates proinflammatory antitumor macrophage polarization in vivo (Schmid et al, 2018;Panni et al, 2019).…”

Key thermally dimorphic fungal pathogens: shaping host immunity

“…Relevant references are indicated in the text. Abbreviations: Hsp60, heat-shock protein 60; Yps3, yeast phase-specific protein-3; CR3, complement receptor 3; VLA-5, very late antigen-5; TLR, toll-like receptor; Mp1, mannoprotein 1; DC-SIGN, dendritic cell-specific ICAM-3-grabbing non-integrin; Gp70, glycoprotein-70 kDa; BAD1, blastomyces adhesin-1; MCL, murine macrophage C-type lectin; MR, mannose receptor; SOWgp, spherule outer‐wall glycoprotein.pathogenphasePAMPPRRreferences Histoplasma capsulatum yeast[β-(1,3) glucan]?Dectin-1[19]Hsp60CR3[20]cyclophilin-AVLA-5 (dendritic cells)[21]Yps3TLR2[22]yeast DNATLR7, TLR9 (dendritic cells)[23] Talaromyces marneffei conidiaunknownTLR1, TLR2, TLR4, TLR6[24]Mp1 mannoproteinunknown[25]conidia/yeastunknownCR3[26]yeastUnknownDC-SIGN (dendritic cells)[27]N-acetyl-β-D-glucosaminyl groupsunknown[28] Coccidioides spp.spheruleunknownTLR2[29][β-(1,3) glucan]?Dectin-1[30]mannoseMR[31,32]SOWgp?…”

“… pathogen phase PAMP PRR references Histoplasma capsulatum yeast [β-(1,3) glucan]? Dectin-1 [ 19 ] Hsp60 CR3 [ 20 ] cyclophilin-A VLA-5 (dendritic cells) [ 21 ] Yps3 TLR2 [ 22 ] yeast DNA TLR7, TLR9 (dendritic cells) [ 23 ] Talaromyces marneffei conidia unknown TLR1, TLR2, TLR4, TLR6 [ 24 ] Mp1 mannoprotein unknown [ 25 ] conidia/yeast unknown CR3 [ 26 ] yeast Unknown DC-SIGN (dendritic cells) [ 27 ] N-acetyl-β-D-glucosaminyl groups unknown [ 28 ] Coccidioides spp. spherule unknown TLR2 [ 29 ] [β-(1,3) glucan]?…”

“…In response to T. marneffei , murine macrophages were shown to upregulate the expression of CD11b , and the inhibition of CD11b significantly reduced phagocytosis of the yeast. This recognition led to the secretion of IFN- γ , TNF-α, IL-4, IL-10 and IL-12 [ 25 , 26 ]. The surface ligand in T. marneffei that binds to CR3 has not yet been identified.…”

“…[24] Mp1 mannoprotein unknown [25] conidia/yeast unknown CR3 [26] yeast Unknown DC-SIGN (dendritic cells)…”