Key Terms
Specificity
The ability to target specific pathogens; protection against one pathogen does NOT protect against others.
Memory
The ability to respond faster and stronger to a pathogen encountered before.
Primary response
Slower, lower antibody levels, ~10 day lag before detectable antibody.
Secondary response
Faster (lag reduced to days), higher antibody concentration, longer lasting, higher affinity antibodies. IgG dominates t
Humoral immunity
Mediated by B cells and the antibodies they produce; targets pathogens and toxins in EXTRACELLULAR environments.
Cellular immunity (cell-mediated immunity)
Mediated by T cells; targets pathogens INSIDE host cells.
Antigen (immunogen)
A molecule that activates adaptive immunity; unique to a specific pathogen (unlike PAMPs, which are shared across many p
Epitope
A small, specific region on the surface of an antigen that is actually recognized by antibodies or T cells. One antigen
Hapten
A small molecule that is essentially a free epitope — too small to be antigenic alone. Must attach to a carrier protein
Bacteria
Capsules, cell walls, fimbriae, flagella, pili, extracellular toxins, enzymes. Viruses: capsids, envelopes, spike struct
Molecular class (ranked most to least antigenic)
1. Proteins - most antigenic; stimulate BOTH humoral and cellular immunity.
Structural complexity
More complex three-dimensional structure = more antigenic. Proteins are most antigenic because of their complex 3D struc
Size
Larger molecules have more epitopes and are more antigenic. Very small molecules (haptens) are non-antigenic alone.
Basic monomer structure
Four protein chains held together by disulfide bonds (covalent bonds between sulfhydryl R groups on cysteine amino acids
Fab region
The two "arms" of the Y. "Fragment of antigen binding." The variable region at the far end of the Fab determines epitope