Biology – The immune system | e-Consult
The immune system (1 questions)
Memory cells are a crucial component of the adaptive immune system, enabling a rapid and robust secondary immune response. These cells are long-lived lymphocytes (either B or T cells) that have been primed by exposure to an antigen during a primary immune response. Upon subsequent encounters with the same antigen, memory cells are rapidly activated, leading to a faster and more effective immune response than the initial response.
There are two main types of memory cells:
- Memory B cells: These cells are characterized by the expression of high-affinity antibodies and are readily activated by antigen binding. Upon re-exposure to the antigen, they rapidly differentiate into plasma cells, which produce large quantities of antibodies specific to the antigen. This leads to a faster antibody response and higher antibody titers.
- Memory T cells: There are different subsets of memory T cells, including central memory T cells (TCM) and effector memory T cells (TEM). TCM cells circulate in lymphoid organs and are poised for rapid activation. TEM cells reside in peripheral tissues and can quickly respond to local antigen stimulation. Upon antigen re-encounter, memory T cells rapidly proliferate and differentiate into effector T cells (e.g., cytotoxic T lymphocytes or helper T cells), initiating a swift and powerful cellular immune response.
The key to the faster and stronger secondary response lies in the fact that memory cells require less stimulation to become activated compared to naive lymphocytes. They express higher levels of receptors for the antigen and are often already in a quiescent state, ready to respond quickly. This results in:
- Faster activation: Memory cells are activated much more rapidly than naive lymphocytes.
- Increased numbers of effector cells: The rapid proliferation of memory cells leads to a larger population of effector cells.
- Higher affinity antibodies: Memory B cells produce antibodies with higher affinity for the antigen due to affinity maturation during the primary response.