The immune system: sources & model

Explore how the immune system responds to an infection. Follow immune cells from skin to lymph node, inspect an antibody structure, and discover what immune memory leaves ready.

What supports the explanation?

What this model assumes

1. Events are retimed explanatory stages, not hours or days. No infection growth, antibody concentrations, health score or treatment outcome is calculated.
2. A few selected cells stand for roles. The picture does not count immune cells or show their real proportions. A missing selected match does not mean a person has no other compatible cells.
3. The two displayed bacterial targets illustrate different routes. Their processing is not evidence that a real infection has cleared. Inflammation also needs regulation and resolution.
4. Source cell pictures are credited medical illustrations, not photographs or 3D cell reconstructions. The original skin, routes and molecular symbols are schematic.
5. The antibody surface is a smoothed envelope of retained heavy-atom coordinates. It is not a solvent-accessible surface or experimental density map. Hydrogen and zero-occupancy atoms are omitted; deposited glycans are retained.
6. Scope: one T-dependent protein-antigen response: This qualitative scenario concerns a protein antigen on a generic extracellular bacterium. It omits T-independent antibody responses, infected-cell killing, complement, tolerance mechanisms and detailed helper-cell subsets. The grouped activation/help setting stands for multiple biological prerequisites; it is not one universal molecular switch.
7. Clonal selection and linked recognition: A repertoire of differently recognizing cells already exists. Here, exact A/B/C labels define an authored compatibility relation. A B receptor recognizes intact antigen, then the cell can process it for peptide–MHC II presentation to a compatible helper. Real affinity, cross-reactivity, HLA variation and the full receptor repertoire are not computed.
8. Compartments and anatomical scale: Blood carries cells; lymphatics connect tissue with draining nodes. The scene separates these routes, then abbreviates efferent lymph, blood circulation and tissue access for returning antibodies. NIH cell and node illustrations are flat images placed in an authored 3D scene. Added B/T regions are explanatory overlays, not a reconstruction of a measured node. Cell, molecule, vessel and organ scales are independently enlarged.
9. Recognition is not the whole effector mechanism: Fab regions include the antigen-binding arms. Fc can engage effector mechanisms, including suitable phagocyte receptors. Closing Fc access here disables only the selected antibody-assisted uptake route. It does not disable every innate pathway or imply that all antibodies have the same effector action.
10. Memory versus continuing secretion: A memory B cell can participate in a recall response. A plasma cell is specialized for secretion. The comparison board records which components are available, without imposing a clinical protection duration, antibody concentration or a fixed number of days to clearance.
11. A real structure has a specific identity: The molecular view uses biological assembly 1 of PDB 1IGT: mouse IgG2a Mab231, studied against a canine lymphoma target. It contains two heavy chains, two light chains and two deposited glycan chains. It is a separate physical example, not an antibody known to bind our fictional protein A. The asymmetric deposited pose is preserved; display separation is not measured molecular motion.

What has been checked

Analytical reference cases, conservation or transition invariants, finite drawing commands, bounded setup parsing, discovery and route integrity are checked automatically. These checks do not establish anatomical fidelity, learner outcomes or browser/device compatibility. Independent subject review, learner trials, comprehensive accessibility review and browser video encoding checks remain pending.

Each source supports the associated claim. Sources do not certify this implementation or its visuals.

About the cover illustration

Original offline rendering derived from PDB 1IGT biological assembly 1, with two heavy, two light and two glycan chains. Deposited data are CC0; teaching colors and envelope processing are recorded in the lesson. It is not a photograph of immune cells or a live antibody movie.