TITLE:
Fc receptors: Cell activators of antibody functions
AUTHORS:
Carlos Rosales, Eileen Uribe-Querol
KEYWORDS:
Immunoglobulin; Antibody; Immunoreceptor; Neutrophil; Macrophage
JOURNAL NAME:
Advances in Bioscience and Biotechnology,
Vol.4 No.4A,
April
29,
2013
ABSTRACT:
At the onset of an infection early defense systems,
such as complement, get into action. Specialized leukocytes (white blood
cells) of the innate immune system,
including monocytes, macrophages, and neutrophils also participate as
a first line of defense against infections. These early responses are rapid but
not very specific and are usually not enough
to clear completely many infections. The adaptive immune system is
also needed to finish the job against many microorganisms. Antibody
molecules, produced during the adaptive immune response, are crucial for
preventing recurrent infections. Although, IgG antibodies are essential for
controlling infections, these molecules do not directly damage the
microorganisms they recognize. Today, it is established that leukocytes of
the innate immune system are responsible for the protective effects of these
antibodies. IgG molecules bind to their cognate antigens and are in turn recognized
by specific receptors (Fcγ receptors)
on the membrane of leukocytes. Crosslinking these receptors on the surface of
leukocytes leads to activation of several effector cell functions. These
effector functions are geared toward the destruction of microbial pathogens and
the induction of an inflammatory state that is beneficial during infections.
However, in autoimmune diseases, antibodies can direct these effector
functions against normal tissues and cause severe tissue damage. In recent
years, several factors that can modulate the IgG-FcγR interaction have been elucidated. In this review, we describe
the main types of Fcγ receptors, and
our current view of how antibody variants interact with these receptors to
initiate different cell responses. In addition, new findings on the signaling
role of individual Fcγ receptors are
also discussed.