Table 1.
Studies primarily evaluating the role of IgM memory B cells in COVID-19.
| Author(year) | Country | Type of study | Population | SARS-Cov-2 vaccination | Subset of MBC | Time of evaluation of IgM MBC | Comments |
|---|---|---|---|---|---|---|---|
| Tian X et al. (31) (2022) |
China | Observational | 31 convalescent children (0-14 years) with mild COVID-19 | NA | -IgM -IgG -IgA |
At baseline and at 6-8 months | Higher proportion of recovering patients with IgM+ B cells than IgG+
IgG+ memory response increases with age as opposed to IgM+ and IgA+ |
| Newell K et al. (15) (2021) |
U.S. | Observational | 40 COVID-19 non-hospitalized patients at baseline 15 also sampled at 3 months 24 healthy subjects |
NA | -CD27+, IgD+, -CD27+ switched memory -CD24- |
-69 days after symptoms onset -3 months |
IgM memory B cells correlate with virus specific antibodies (IgG1 and IgM) and are stable at 3 months |
| Mazzoni A et al. (32) (2021) |
Italy | Experimental | 22 individuals; of which 11 with previous infection | mRNA (II doses) | -CD27+ IgM+ memory -CD27+ IgA -CD27+ IgG |
7, 14, 21, 28 days | IgM+ increase only after II dose in COVID-19-naïve individuals, while they increase after I dose in those who had COVID-19 |
| Anand S et al. (33) (2021) |
Canada | Observational | 32 convalescent individuals sampled up to 31 weeks (n=13) | NA | -IgM | 6,11,21,31 weeks | IgM+ decrease over time while IgG+ are stable |
| Yang J et al. (34) (2021) |
China | Observational | 55 recovered patients, 55 healthy donors |
NA | -IgM+
-IgM- |
On average 42.2 days after discharge | Lower frequency of IgM isotype-switched memory B cells in recovered patients as compared to heathly donors |
| Piepenbrink M et al. (35) (2021) |
U.S. | Experimental | Hamsters | NA | IgM MBC | Acute infection | Intraperitoneal/aerosol delivery of a human mAb derived from a COVID19 RBP specific IgM memory B cell reduces respiratory tract viral burden/pathology |
| Lenti MV et al. (36) (2020) |
Italy | Observational | 63 patients, 3 splenectomised patients excluded | NA | IgM+ IgD+, CD27+ | Acute infection, median 25 days | IgM MBC depletion in 87% of patients |
| De Biasi S et al. (37) (2020) |
Italy | Observational | 14 hospitalized patients with pneumonia 11 healthy subjects as controls |
NA | -IgM MBC -switched -unswitched |
Acute infection, 2-4 days following admission | Decreased number of MBC |
MAb, monoclonal antibody; MBC, memory B cell, NA, not assessed.