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Development of macrophage anticryptococcal activity in vitro is dependent on endogenous M-CSF
E Brummer1, G L Gilmore, R K Shadduck
1Department of Medicine, Santa Clara Valley Medical Center, and California Institute for Medical Research, San Jose, California, 95128, USA.
Abstract:
We previously showed that nonactivated resident murine peritoneal macrophages (PM) from five strains (e.g., BALB/c) have C'-dependent fungistasis for Cryptococcus neoformans in 24-h coculture, but not CD-1 PM unless culture time was extended or M-CSF treatment was used. We studied effect of a rat IgG1 monoclonal (m) antibody (Ab) to murine M-CSF receptor on this anticryptococal activity. Culture of BALB/c PM with mAb, diluted 1:10, prechallenge reduced fungistasis from 58 to 21% (P < 0.01), whereas further 10-fold dilutions did not. Moreover, M-CSF pretreatment (5000 U/ml) significantly enhanced fungistasis (to 85%), whereas adding mAb 1:10 or 1:100 reduced that (to 58 and 77%, respectively, P < 0.01). In 48-h culture CD-1 PM had 39% fungistasis, reduced to 0% by mAb, M-CSF treatment of CD-1 PM increased fungistasis to 72%, which was reduced to 13 or 58% (P < 0. 001) by 1:10 or 1:100 mAb, respectively. Complete blocking by mAb of CD-1 PM activity was consistent with lack of measurable early endogenous CD-1 M-CSF production. Increasing exogenous M-CSF could overcome the inhibition by mAb (64% fungistasis BALB/c PM reduced to 11% with inhibition by mAb or increased to 94% with 5000 U/ml M-CSF; 37% with both mAb and M-CSF, 51% with mAb and 10,000 U/ml; P < 0.05, 5000 U/ml + mAb vs 10,000 U/ml + mAb). Moreover, rabbit Ab to M-CSF significantly reduced anticryptococcal activity of untreated BALB/c macrophages. In summary, development of PM fugistatic activity is dependent on endogenous M-CSF, since it is blocked by anti-receptor mAb (as is exogenous M-CSF stimulation) or anti-M-CSF Ab, and macrophages of the mouse strain with delayed activity had no measurable early M-CSF production.
Insights
Resident macrophages exhibit fungistasis against Cryptococcus neoformans, a process dependent on macrophage colony-stimulating factor (M-CSF). Blocking M-CSF signaling inhibits this antifungal activity, highlighting M-CSF
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Resident murine peritoneal macrophages (PM) display complement-dependent fungistasis against Cryptococcus neoformans.
- This antifungal activity varies between mouse strains, with CD-1 PM showing delayed fungistatic capacity compared to BALB/c PM.
- Macrophage colony-stimulating factor (M-CSF) is a key cytokine involved in macrophage differentiation and function.
Purpose of the Study:
- To investigate the role of M-CSF in the development of fungistatic activity in murine peritoneal macrophages.
- To determine if blocking the M-CSF receptor affects the anticryptococcal activity of macrophages.
- To assess the impact of exogenous M-CSF and M-CSF receptor blockade on macrophage fungistasis.
Main Methods:
- Treatment of murine peritoneal macrophages with a rat IgG1 monoclonal antibody (mAb) against the M-CSF receptor.
- Coculture of treated or untreated macrophages with Cryptococcus neoformans for 24 or 48 hours.
- Assessment of fungistasis by quantifying fungal growth inhibition.
- Pretreatment of macrophages with M-CSF and subsequent blockade with anti-M-CSF receptor mAb.
- Treatment of macrophages with rabbit anti-M-CSF antibody.
Main Results:
- A monoclonal antibody targeting the M-CSF receptor significantly reduced fungistasis in BALB/c and CD-1 macrophages.
- M-CSF pretreatment enhanced fungistasis, an effect diminished by the M-CSF receptor antibody.
- CD-1 macrophages, exhibiting delayed fungistatic activity, showed complete blockade of activity by the M-CSF receptor antibody, correlating with low endogenous M-CSF production.
- Exogenous M-CSF could overcome M-CSF receptor antibody-mediated inhibition, and anti-M-CSF antibody reduced macrophage anticryptococcal activity.
Conclusions:
- The development of peritoneal macrophage fungistatic activity against Cryptococcus neoformans is dependent on endogenous M-CSF.
- M-CSF signaling, via its receptor, is crucial for mediating this anticryptococcal defense.
- Targeting M-CSF or its receptor represents a potential strategy to modulate macrophage antifungal immunity.