Doctoral Candidate University of Texas Medical Branch, United States
Disclosure(s):
Reina Paez: No financial relationships to disclose
Introduction/Rationale: Macrophage galactose-type lectin (MGL) is an important modulator of inflammation in various disease settings. While humans possess a single MGL molecule (hMGL/CLEC10A), mice have two homologs of the receptor (mMGL1/Clec10a and mMGL2/Mgl2) that may have overlapping functions with hMGL. We have previously demonstrated that mMGL1 plays an important role in the immune response to Mycobacterium tuberculosis (Mtb) infection by limiting inflammation and augmenting antibacterial activity of macrophages. In contrast, the effects of mMGL2 or mMGL1/2 deficiency have yet to be investigated due to the lack of available knockout mouse models.
Methods: To address this gap, we generated novel mouse lines that lack mMGL2 alone or in combination with mMGL1 via CRISPR-Cas9 mediated disruption of Mgl2 on the B6.129-Clec10atm1Hed/J background. In vitro assessment was performed in bone marrow derived macrophages (BMDM) from WT, mMGL1 KO, mMGL2 KO, and mMGL1/2 KO mice. Additionally, male and female WT, mMGL2, and mMGL1/2 mice were infected with 400 CFU Mtb via aerosol, and microbiological, immunological, and histological outcomes were assessed 8 weeks post-infection.
Results: Our in vitro killing assay confirmed that while mMGL1 KO macrophages exhibit significantly higher Mtb burden compared to WT, there was only a modest increase in bacterial burden in mMGL2 KO BMDM and no difference between WT and mMGL1/2 BMDM. In contrast, our preliminary in vivo study showed no difference in lung bacterial burden between WT and mMGL2 KO and significantly reduced bacterial burden in mMGL1/2 KO mice. Interestingly, assessment of lung cytokine levels revealed that mMGL2 KO mice exhibit more pro-inflammatory cytokine production (e.g., IL-1β) than WT counterparts. In comparison, mMGL1/2 KO mice had generally similar or depressed cytokines compared to WT, consistent with microbiological outcomes.
Conclusion: These results highlight the functional divergence of mMGL1 and mMGL2 in the murine immune response to Mtb.
