Researchers at the University of Osaka have identified cellular features that may explain why some antibody responses persist for years while others decline more rapidly. Using a mouse model, the investigators found that B cells producing IgG1 antibodies possess several advantages that promote their survival, expansion, and migration to the bone marrow, where long-lived antibody-producing cells can become established.
Antibodies are a key component of the immune response to infection. Following exposure to a pathogen, B cells initially produce immunoglobulin M (IgM), an early antibody that helps provide immediate protection. Some B cells subsequently undergo class switching, a process in which they change the type of antibody they produce while retaining their ability to recognize the same antigen. IgG1 is one such antibody subclass and is frequently associated with durable immune responses. These B cells can eventually differentiate into plasma cells, specialized immune cells that continuously produce and secrete antibodies.
However, the cellular mechanisms that determine why some antibody-producing cells survive for extended periods have remained incompletely understood. To investigate this question, the researchers compared IgM- and IgG1-producing immune cells and examined whether differences in their cellular behavior could account for the greater durability of IgG1 responses. The researchers found that B cells that had switched to IgG1 demonstrated an enhanced ability to present pathogen-derived antigens to T cells before differentiating into plasma cells. This improved antigen presentation strengthened interactions between B cells and T cells, providing signals that supported the proliferation and development of newly generated IgG1-producing plasma cells.
The study also identified differences in cell survival. IgG1-producing plasma cells displayed a survival advantage before reaching the bone marrow, whereas IgM-producing cells in the spleen were more susceptible to apoptosis, the programmed process through which the body eliminates damaged or unnecessary cells. Greater resistance to apoptosis may allow IgG1-producing cells to persist for longer periods during the development of an immune response, increasing their likelihood of contributing to long-term antibody production.
Migration to the bone marrow represented another important difference between the two cell populations. IgG1-producing plasma cells were more efficient at leaving the spleen and reaching the bone marrow. The bone marrow provides specialized survival signals and cellular niches that allow plasma cells to persist for extended periods and continuously release antibodies into the circulation. Establishment within these niches is considered an important step in generating long-lasting humoral immunity. The findings suggest that class switching from IgM to IgG1 may do more than alter the type of antibody produced by a B cell. It may also influence the cell’s behavior, survival, migration, and eventual fate.
Lead co-author Takuya Koike noted that IgG1-producing B cells were better able to present pathogen-derived antigens to T cells, helping newly formed IgG1-producing plasma cells expand. Together, these properties may help explain why IgG1 responses are particularly capable of establishing long-term antibody production.
The study provides new insights into how the immune system naturally generates durable antibody responses. Although the investigation focused specifically on IgG1-producing cells in mice, the researchers suggest that related mechanisms could potentially operate with other antibody isotypes, including IgA and IgE. Further studies will be needed to determine whether similar mechanisms occur in humans and whether they can be harnessed to improve immune protection.
Understanding the cellular features that favor the formation and survival of long-lived plasma cells could ultimately aid vaccine research. By identifying strategies that promote the survival, expansion, and migration of antibody-producing cells to the bone marrow, future vaccines might be designed to generate stronger and more persistent protection against infectious diseases.
Reference
- Tai Y, Koike T, Yamamoto H, Shida K, Engels N, Inoue T, et al. Positive selection of IgG over IgM plasma cells through BCR isotype–specific antigen presentation and signaling. Sci Immunol. 2026.