Role of Memory Cells
A defining feature of the adaptive immune system is its ability to generate memory cells following an initial exposure to an antigen. Both B cells and T cells can develop into memory cells after their initial activation.
Memory cells are long-lived and remain in the body even after the pathogen has been cleared. They have a heightened sensitivity to their specific antigen and can respond more quickly and effectively upon subsequent exposures. This rapid response often prevents the pathogen from causing illness again.
An immune response graph visually represents the immune system’s reaction to a pathogen over time.
Lag Phase: At the start of the graph, following initial exposure to the pathogen, there is a lag phase. During this period, the immune system is recognising the pathogen and initiating the response. This phase is characterised by low levels of antibodies and immune cell activation.
Primary Immune Response: As time progresses, the graph shows the rise of the primary immune response. This phase involves a gradual increase in antibody levels as B cells are activated and differentiate into plasma cells that produce antibodies specific to the pathogen.
Contraction Phase: After the primary peak, the graph shows a decline in antibody levels as the pathogen is cleared from the body. The immune system reduces its response, and the levels of antibodies decrease.
Secondary Immune Response: If the same pathogen is encountered again, the graph shows a secondary immune response. This phase is characterised by a faster and more robust immune response due to the presence of memory cells. Antibody levels rise quickly, and T cell activity increases rapidly. The peak of the secondary response is typically higher and occurs more rapidly than the primary response, reflecting the enhanced efficiency of the immune system’s memory.
Vaccination and Immunity:
This principle of memory cells is utilised in vaccination. Vaccines introduce a harmless form of the antigen, which stimulates the production of memory cells without causing disease. When the actual pathogen is encountered later, these memory cells facilitate a swift immune response, providing protection against illness.