Read Immune Cells by Lineage and Trigger
Read immune-system questions by tracing a cell’s lineage, the signal it detects, and the response it produces.
Living-system questions are solved by matching a structure or organism to its function, process and stated condition.
Use missing-self recognition
Most normal nucleated cells display MHC-I. Natural killer cells are restrained by that normal MHC-I signal and can kill stressed, tumour or virus-infected cells when MHC-I is reduced or absent. This is missing-self recognition; it differs from conventional T-cell antigen recognition.
Link IgE to allergy
IgE binds Fc receptors on mast cells and basophils. When an allergen cross-links the bound IgE, those cells degranulate and release mediators such as histamine, producing an allergic response. Keep IgE distinct from the IgG-dominated secondary-response pattern.
Trace the blood-cell lineage
Lymphoid stem cells give rise to T lymphocytes after thymic maturation, B lymphocytes that can become plasma cells, and NK cells. Myeloid stem cells give monocytes that become macrophages, alongside granulocytes, erythrocytes and megakaryocytes. In a lineage diagram, follow the thymus, plasma-cell and monocyte arrows before naming the labelled cells.
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- ✓Loss of MHC-I can activate NK-cell killing.
- ✓IgE cross-linking on mast cells/basophils releases histamine.
- ✓Thymus marks T-cell maturation; monocytes become macrophages.
Do not treat every lymphocyte as a conventional antigen-recognising T cell. The missing-self clue specifically points to NK cells.
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