Measurement of the Memory B Cell Response via Antibodies from Activated Cells.

Background/objectives: The body's immune response to infections and vaccination leads to the formation of memory B cells (MBCs), which protect against future infections. MBCs circulate in the blood, and the strength of the MBC response is measured with different tests. In this study, tests to measure the MBC response were compared.

Methods: An MBC enzyme-linked immunospot assay (MBC-ELISpot), which counts the antibody-releasing cells (MASCs) that arise from memory B cells in vitro, and two versions of an MBC enzyme-linked immunosorbent assay (MBC-ELISA), which measures the concentration of antibodies released by the MASCs, were compared. The lower measurement limit of MBC-ELISpot and ELISA was determined, and it was investigated how the measurement results of individual samples and in a sample of test persons correlate.

Results: Both methods had similar lower limits of detection, and the antibody concentration correlated strongly with the number of MASCs in individual samples. The antibody concentrations measured on a sample correlated with Pearson correlation coefficients of R = 0.83-0.87 with the number of MASCs, and the proportion of antigen-specific antibodies in total IgG correlated with R = 0.74-0.82 with the proportion of antigen-specific MASCs in all antibody-secreting cells.

Conclusions: Since the measurement sensitivity of MBC-ELISA and MBC-ELISpot is similar and the measurement results correlate strongly in a random sample, the tests are interchangeable. The MBC-ELISA has an advantage over the ELISpot in that the antibody measurements can be divided up over time, repeated, and extended. This creates new possibilities for measuring the MBC response.