A group from University de Monterey, etc. has reported an evaluation result of SARS-CoV-2 neutralization activities of IgM, IgA, and IgG using plasma samples from 25 convalescent patients with the new coronavirus (COVID-19).
https://pubmed.ncbi.nlm.nih.gov/33596407/
IgM, IgA, and IgG were selectively depleted using isotype-specific ligands immobilized on beads, respectively. A comparison of the SARS-CoV-2 pseudoviral inhibitory dilution (ID50) for each plasma is shown below. In the IgM-depleted plasma, neutralization activity was greatly reduced by 5.5 times, the secondary one was the IgG-depleted plasma with the reduction of 4.5 times, and the reduction of IgA-depleted plasma was 2.4 times. Considering that IgM is only 5% of total immunoglobulin, the neutralization activity of IgM is very curious.
