It is known that there are three type of innate immunity, (1)phagocytosis with phagocytic cells such as macrophages and NK cells, (2)complement lectin pathways, and (3)extra-spherical traps . In the complement lectin pathway, Mannose Binding Lectin (MBL) plays a central role, and when MBL binds to the mannose on the pathogen’s cell membrane, an enzyme called MBL-binding serine protease (MASP) bound to MBL is activated, and MASP activates the complement Factor 4 (C4), which sequentially activates the complements and ultimately kills it by drilling a hole in the pathogen’s cell membrane.
A group of Istanbul Faculty of Medicine, Istanbul Univ. has reported that the genetic variants in MBL are largely related to the severity of covid-19.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7838598/
For the mutation of codon52 of the MBL2 gene,
Referring to AA genotype,
BB genotype: odds ratio (OR) = 5.3, p< 0.001;
AB genotype: OR = 2.9, p = 0.001
For the ICU need, the odds ratios get higher as follows,
BB genotype: OR = 19.6, p < 0.001
AB genotype: OR = 6.9, p = 0.001
This could be a good reference in using MBL as a therapeutic protein.