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FcμR 267 Fc receptors on human T cells
Peptides
pFc´
F(ab´) 2
Pepsin
digestion
comprised of two C terminal heavy chain segments
(C H2, C H3) and a portion of the hinge region linked by the
central disulfide bond and noncovalent forces. This 50-kDa
fragment is unable to bind antigen, but it has multiple
other biological functions, including complement fixation,
interaction with Fc receptors on cell surfaces, and placental
transmission of IgG. One Fc fragment is produced by
papain digestion of each IgG molecule. The Fc region of an
intact IgG molecule mediates effector functions by binding
to cell surface receptors or C1q complement protein.
FcμR
IgM Fc receptors have been described but remain to be
well characterized.
Fc piece
Refer to Fc fragment.
Fc receptor
A structure on the surfaces of some lymphocytes, macrophages,
or mast cells that specifically binds the Fc region
of immunoglobulin, often when the Fc is aggregated.
Effector cells express isoforms FcαcR, FcγR, or FcεR and
activate signaling that mediates receptor-mediated endocytosis,
phagocytosis, and ADCC in addition to neutrophil
and mast cell degranulation with the release of inflammatory
mediators and cytokines. Numerous FcRs belong to the
immunoglobulin (Ig) superfamily and contain ITAMs. The
Fc receptors for immunoglobulin G (IgG) are designated
FcγR. Those for IgE are designated FcεR. IgM and IgD
Fc receptors have yet to be defined. Neutrophils, eosinophils,
mononuclear phagocytes, B lymphocytes, selected T
lymphocytes, and accessory cells bear Fc receptors for IgG
on their surfaces. When the Fc region of immunoglobulin
binds to the cation permease Fc receptor, there is an influx
of Na + or K + that activates phagocytosis, H 2O 2 formation,
and cell movement by macrophages.
Fc receptors on human T cells
Fc receptors (FcRs) are carried on 95% of human peripheral
blood T lymphocytes. On about 75% of the cells, the FcRs
are specific for immunoglobulin M (IgM); the remaining
20% are specific for IgG. The FcR-bearing T cells are also
designated T M and T G or Tμ and Tγ. The T M cells act as
helpers in B cell function. They are required for the B cell
responses to pokeweed mitogen (PWM). In cultures of B
cells with PWM, the T M cells also proliferate, supporting
the views on their helper effects. Binding of IgM to FcR of
IgG
Fc fragment.
Papain
digestion
Fab
Fc
Fab
Fc (IgG) receptor (neonatal).
Fcε RI Fcε RII Fcα R
Fcα and Fcε receptors.
Fcγ RI Fcγ RII Fcγ RIII
Fcγ receptors.
T M cells is not a prerequisite for helper activity. In contrast
to the T M cells, the T G cells effectively suppress B cell differentiation.
They act on the T M cells, and their suppressive
F