Microbiology & Immunity
Explore the diversity of microbes and follow how innate defenses, antigen-specific B and T cells, and immune memory interact.
See how the pieces connect
- Step 1Pathogen or vaccine antigenan immune system may encounter a molecular target
- Step 2Innate defensessense broad signs and shape the response
- Step 3Antigen presentationpeptide–MHC complexes can be recognized by T cells
- Step 4Adaptive responsematching B and T cells can expand
- Step 5Memory B cellsome responses leave cells that persist
A vaccine and an infection can expose the immune system to related antigens, but they are not biologically identical. Innate signals and antigen presentation can help activate adaptive responses. B cells, helper T cells, and cytotoxic T cells have distinct roles, and some activated cells persist as memory. The outcome varies by antigen, platform, host, and time.
Read the supporting reference: NCBI Bookshelf · Principles of Innate and Adaptive ImmunityWhy can a later immune response differ from a first response to a matching antigen?
Topics in this branch
Bacteria
One of the three domains of cellular life, comprising prokaryotic organisms with extensive metabolic and ecological diversity.
Explore this idea 02Archaea
A domain of cellular life distinct from Bacteria and Eukarya, with diverse metabolisms and habitats.
Explore this idea 03Escherichia coli
A diverse bacterial species that includes harmless strains as well as strains associated with disease.
Explore this idea 04Virus
An acellular infectious agent whose replication depends on host-cell machinery.
Explore this idea 05Pathogen
A biological agent that can cause disease in a host under particular conditions.
Explore this idea 06Innate Immune Response
Rapid, pattern-based defenses that limit infection and help activate adaptive immunity.
Explore this idea 07Antigen
A molecular structure that can be specifically recognized by immune receptors or antibodies.
Explore this idea 08Antigen Presentation
Display of peptide fragments on major histocompatibility complex molecules for recognition by T cells.
Explore this idea 09Adaptive Immune Response
Antigen-specific B- and T-cell responses that can form immunological memory.
Explore this idea 10Vaccination
An intervention that presents antigenic information to the immune system to help establish protective responses and memory.
Explore this ideaImmune Cells and Molecules
Dendritic Cell
Dendritic cells collect and process material, then can show antigen fragments to T cells.
Open record Cell typeB Cell
A lymphocyte whose activated descendants can secrete antibodies and form memory cells.
Open record Cell typeHelper T cell
A CD4⁺ T lymphocyte that coordinates immune responses through cell contacts and secreted signals.
Open record Cell typeCytotoxic T cell
A CD8⁺ T lymphocyte that can kill target cells displaying recognized peptide–MHC class I complexes.
Open record Cell typeMemory B Cell
Memory B cells can persist after an immune response and respond more quickly if a related antigen appears again.
Open record Molecular complexAntibody
An antigen-binding immunoglobulin made by B-lineage cells that can neutralize targets or recruit other immune mechanisms.
Open record