Humoral immunity

Involves antibodies.

Primary response
IgM is the main Ab isotype produced in primary infection. It is found in the blood.

Secondary response
Involves improved response due to T cell help to create antibodies.

Note that the lack of improved response upon secondary immunization is characteristic of a T cell independent Ab response.

Key preferred characteristics include:
 * Shorter lag time post-immunization before Ab responses are detectable
 * Increased peak magnitude of the Ab response over the primary response
 * Long-lasting increase in antibody titers