The immune response and memory cells
The immune response
- The first time a new pathogen enters, the response is slow.
- Several cell types work together to destroy it — and to remember it.
- That memory is what makes you immune next time.
The primary response
- a macrophage engulfs the pathogen and displays its antigen.
- T-helper cells recognise that antigen, become active, and switch on other cells.
- matching B-lymphocytes are selected; they divide into plasma cells (which pour out antibodies) and memory cells.
- T-killer cells destroy the body's own cells that are infected.
Practice
T-helper cells in the immune response:
T-helper cells recognise the presented antigen and activate B-lymphocytes and other cells.
Practice
Which cells actually secrete antibodies?
Selected B-lymphocytes divide into plasma cells (which secrete antibodies) and memory cells.
Practice
Put the primary immune response in order.
Antigen presented → T-helper activated → B-lymphocytes selected → plasma cells make antibodies.
Memory and the secondary response
- Memory cells stay in the body for years.
- If the same pathogen returns, they launch a secondary response that is much faster and larger.
- The pathogen is destroyed before it makes you ill — long-term immunity.
Practice
The secondary immune response is faster and larger because:
Memory cells made in the primary response respond quickly and strongly when the same pathogen returns.
You've got it
Key idea
- primary response: macrophage displays antigen → T-helper activates → B-lymphocytes → plasma cells (antibodies) + memory cells
- T-killer cells destroy infected body cells
- memory cells persist; the secondary response is faster and larger
- that's long-term immunity — the pathogen is cleared before you fall ill