What is the basis of immunological memory?
The basis of immunological memory lies in the generation and maintenance of memory B cells and memory T cells. These specialized immune cells are formed during an initial infection or vaccination and provide long-term protection against future encounters with the same pathogen. Here's how immunological memory works:
1. Antigen Recognition:
During an infection, antigen-presenting cells (APCs) capture and present pathogen-derived antigens to immune cells. These antigens are recognized by B cells and T cells, which become activated and proliferate.
2. Formation of Memory B Cells:
Activated B cells differentiate into plasma cells, which produce antibodies specific to the antigen. Some B cells further develop into memory B cells. These cells have a long lifespan and remain in the body after the infection is cleared.
3. Formation of Memory T Cells:
Activated T cells also give rise to memory T cells. There are two main types of memory T cells: central memory T cells (Tcm) and effector memory T cells (Tem). Tcm cells reside in lymphoid tissues, while Tem cells circulate throughout the body, providing rapid immune responses.
4. Antigen Re-exposure:
Upon re-exposure to the same pathogen, memory B cells and memory T cells quickly recognize the antigen. This recognition triggers a rapid and robust immune response.
5. Antibody Production and Cell-Mediated Immunity:
Memory B cells rapidly differentiate into antibody-producing plasma cells upon re-exposure to the antigen. These antibodies neutralize the pathogen, preventing infection. Memory T cells can directly destroy infected cells or activate other immune cells to eliminate the pathogen.
6. Booster Effect:
Subsequent encounters with the same pathogen further enhance immunological memory. This is known as the booster effect. Each subsequent exposure leads to a more rapid and robust immune response, providing better protection against the pathogen.
Immunological memory is crucial for long-term immunity and protection against infections. It enables the immune system to respond swiftly and effectively to previously encountered pathogens, preventing or minimizing the severity of subsequent infections.