How do antibodies work?
Antibodies are proteins made by plasma cells that bind particular antigen structures.
Biological mechanism and regulation
The variable region recognizes a target, while the constant region engages phagocytes or complement. Binding may neutralize a toxin or mark a microbe.
Evidence, applications and limits
IgM, IgG, IgA, IgE and IgD differ in role and distribution. Antibody level does not always equal protection, and test timing or cross-reactivity matters. No single molecule or measurement explains the whole system; cell type, timing, environment and feedback must be considered together.
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