Innate sensors
Pattern-recognition receptors start inflammation and antigen presentation within hours.
A first encounter — infection or vaccine — recruits innate cells that display antigen to lymphocytes in lymph nodes.
Clones that fit the antigen expand. Some become short-lived effectors; some become memory. Boosters restimulate that file.
Parts
Lymph node classroom
Dendritic cells meet naive T and B cells. This is where specificity is chosen.
B-cell antibodies
Secreted immunoglobulins bind free antigen. Affinity can mature over weeks.
Cytotoxic T cells
They recognize infected cells by peptide-MHC and can kill those cells.
Memory archive
Long-lived cells and sometimes plasma cells in bone marrow keep a file for later.
Platforms
Inactivated, live-attenuated, subunit, viral-vector and mRNA platforms differ in how antigen is shown, not in the idea of memory.
Life cycle
1Antigen arrives
A vaccine or infection delivers shapes the innate system flags as worth learning.
2Clonal class
Matching B and T cells multiply. Antibodies class-switch; killers learn peptides.
3Effector wave
Short-lived cells try to clear antigen. Fever and sore arms are common side-effects of that activity.
4Memory file
A smaller set of cells remains. Later exposure can be faster and often milder.
Formulation details that would amount to a medical order are omitted. The cycle is the concept.
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