Year 11 / Infectious disease and epidemiology

The second encounter.

Innate defences act rapidly and broadly: barriers, inflammation and phagocytes limit invasion. Adaptive immunity identifies particular antigens. B cells can make antibodies; T cells help coordinate or kill infected cells.

After an initial response, memory cells remain. A later encounter with the same antigen can trigger a faster, stronger response. Vaccination safely presents antigenic information so memory can form without requiring the disease itself.

INTERACTIVE MODEL

Adaptive immune response

Primary response: slower activation and smaller peakExposureLater exposureFirstLater

Explore: Switch between first and later exposure to compare antibody-response curves.

\text{antigen exposure}\to\text{memory cells}\to\text{faster later response}

WORKED EXAMPLE

Compare antibody levels after first and second exposure to the same antigen.

The first response takes time as specific cells are selected and expanded.
Memory cells accelerate the second response, often yielding a larger peak.

Assumed knowledge

Cells and proteins.

Learning checkpoints & source

YOUR LEARNING CHECKPOINT

Distinguish innate and adaptive defences.
Explain immunological memory and vaccination.

QCAA Biology · Unit 2 · Infectious disease and epidemiology ↗

READY TO TRY IT?

The second encounter.

Adaptive immune response

Compare antibody levels after first and second exposure to the same antigen.

Put the idea to work.