Defense Mechanisms of the Body
Encounter and recognition
Helper T cell
Cytotoxic T cell
NK cells to attack
or to neutralize
Directly attack antigen-
Summary of the roles of B, cytotoxic T, and helper T cells in immune responses. Events of the attack phase are described in later sections.
symbol denotes a stimulatory effect (activation) of cytokines.
Immunoglobulin structure. The Fc portions and an extended region
of the heavy chains are the same for all immunoglobulins of a
particular class. A small portion of the light chains are also the same
for a given immunoglobulin class. Collectively, these portions of
the heavy and light chains are called “constant ends.” Each “prong”
contains a variable amino acid sequence, which represents the single
antigen binding site. The links between chains represent disulﬁ de