Example 1
Antibody level reaches 20 units after first exposure and 100 after a later exposure. Find the fold increase in peak level.
20100=5−fold. This compares peak antibody levels, not necessarily total immunity.
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Year 11 · SACE Stage 1
Adaptive immune responses
Match adaptive components to functions and read primary/secondary response data.
Method and worked examples
Adaptive immunity targets particular antigen features. Suitable B lymphocytes can multiply and differentiate into antibody-secreting plasma cells. Antibodies can neutralise targets or mark them for other immune processes. Helper T cells coordinate responses; cytotoxic T cells kill appropriate infected body cells. T-cell responses involve recognition of presented antigens rather than antibody secretion by T cells.
Some activated lymphocytes become memory cells. On later exposure to the same antigen, a secondary response is often faster and stronger than the primary response. Lymph nodes and the spleen are secondary lymphoid organs where immune cells encounter antigens and responses develop. Innate and adaptive components cooperate; antibodies do not act as a complete independent defence system on their own.
Example 1
Example 2
A cell secretes large amounts of antigen-specific antibody. Identify its type.
It is a plasma cell derived from an activated B lymphocyte.
Watch out: Plasma cells derived from B lymphocytes secrete antibodies; T cells have coordinating or cell-killing roles.