Immunology Basics - Immunological Computation: Theory and Applications - page 9

pathogenic microorganisms. h is ingestion has two purposes: to kill the anti-
gen and to present fragments of the invader's proteins to other immune cells
and molecules.

Infl ammatory response . Activated macrophages produce cytokines (hormone-
like protein messengers), which induce the infl ammatory response character-
ized by vasodilation and rise in capillary permeability. h ese changes allow a
large number of circulating immune cells to be recruited to the site where an
infection occurs.

1.2.3 Adaptive Immunity

Adaptive immunity (Kuby et al., 2000; Stanley, 2002), also called acquired or spe-
cifi c immunity, represents the part of the immune mechanism that is able to spe-
cifi cally recognize and selectively eliminate foreign microorganisms and molecules.
Adaptive immunity produces two types of responses in the presence of pathogens:
humoral immunity and cellular immunity. h e humoral immunity is based on the
synthesis of antibodies by B cells; however, in cellular immunity, T cells cause the
destruction of microorganisms that carry invading antigens and those self-cells that
have been infected.

Humoral immunity . Humoral immunity is mediated by antibodies contained
in body fl uids (known as humors). h e humoral branch of the immune sys-
tem involves B cell/antigen interaction, and the subsequent proliferation and
diff erentiation of B cells into antibody-secreting plasma cells. Antibodies
function as eff ectors of the humoral response by binding to antigens and
facilitating their elimination.

Cellular immunity . Cellular immunity is cell-mediated; thus, eff ector T cells,
generated in response to an antigen, are responsible for cell-mediated immu-
nity. Cytotoxic T lymphocytes (CTLs) participate in cell-mediated immune
reactions by killing altered self-cells; they play an important role in killing
virus-infected- and tumor cells. Cytokines secreted by T DH cells can medi-
ate cellular immunity, and activate various phagocytic cells, enabling them
to kill microorganisms more eff ectively. h is type of cell-mediated immune
response is especially important in host defense against intracellular bacteria
and protozoa (Abbas and Lichtman, 2004; Todd and Spickett, 2005).

1.3 Immune System Dynamics

h e mechanisms that defi ne the immune system's dynamic behavior are explained
in this section.