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cell-bound antibody (cell-fixed antibody) 159 cell separation methods
Most are grouped into protein families that include the
integrins, selectins, mucin-like proteins, and the immunoglobulin
superfamily.
cell-bound antibody (cell-fixed antibody)
An antibody anchored to the cell surface either through its
paratopes binding to cell epitopes or attachment of its Fc
region to Fc receptors. An example is cytophilic antibody or
IgE which may then react with antigens as their Fab regions
are available.
cell cooperation
T lymphocyte and B lymphocyte cooperation.
cell line
Cultured neoplastic cells or normal cells that have been
transformed by chemicals or viruses. Transformed cell lines
may be immortal, enabling them to be propagated indefinitely
in culture.
cell-mediated hypersensitivity
Refer to delayed-type hypersensitivity and to type IV cellmediated
hypersensitivity.
cell-mediated immune response
Host defense mediated by antigen-specific T lymphocytes
together with nonspecific cells of the immune system. The
response offers protection against intracellular bacteria,
viruses, and neoplasms and mediates graft rejection. It may
be transferred passively with primed T lymphocytes.
cell-mediated immunity (CMI)
The limb of the immune response mediated by antigenspecific
effector T cells that produce their effect through
direct reaction, in contrast to the indirect effect mediated by
antibodies of the humoral limb produced by B lymphocytes.
CMI also includes the effector functions of natural killer
(NK) and NKT cells. The development of cell-mediated
immunity to an exogenous antigen first involves processing
of the antigen by an antigen-presenting cell such as a macrophage.
Processed antigen is presented in the context of
major histocompatibility complex (MHC) class II molecules
to a CD4 + T lymphocyte. IL1β is also released from the
macrophage to induce IL2 synthesis in CD4 + lymphocytes.
The IL2 has an autocrine effect on the cells producing it,
causing their proliferation and also causing proliferation
of other lymphocyte subsets including CD8 + suppressor/
cytotoxic T cells, B lymphocytes that form antibodies, and
NK cells. Cell-mediated immunity is critical in defenses
against mycobacterial and fungal infections and resistance
to tumors, and it has a role in allograft rejection.
4–5 days
added
3 hours
Cell-mediated lympholysis test.
cell-mediated immunodeficiency syndrome
Condition in which cell-mediated immunity is defective. It
may be manifested as negative skin test results following the
application of tuberculin, histoplasmin, or other common
skin test antigens; failure to develop contact hypersensitivity
following application of sensitizing substances such as dinitrochlorobenzene
(DNCB) to the skin; or failure to reject an
allograft, such as a skin graft. Severe combined immunodeficiency
(SCID) is characterized by defective T lymphocyte
and B lymphocyte limbs of the immune response. DiGeorge
syndrome is characterized by failure of development of the
T-cell-mediated limb of the immune response.
cell-mediated lympholysis (CML) test
Responder (effector) lymphocytes are cytotoxic for donor
(target) lymphocytes after the two are combined in culture.
Target cells are labeled by incubation with 51 Cr at
37°C for 60 minutes. Following combination of effector
and target cells in tissue culture, the release of 51 Cr from
target cells injured by cytotoxicity represents a measure of
cell-mediated lympholysis (CML). The CML assay gives
uniform results, is relatively simple to perform, and is rather
easily controlled. The effector cells can result from in vivo
sensitization following organ grafting or can be induced in
vitro. Variations in the ratio of effector to target cell can be
employed for quantification.
cell separation methods
Early cell separation techniques were based in the
early 1960s on differences such as cell size and density.
Subsequently, membrane receptors or surface antigens were
found to be differently expressed by lymphocyte subsets.
Currently, the most popular lymphocyte separation techniques
include immunoselection procedures that employ
monoclonal antibodies. The two methods used for lymphocyte
separation based on physical differences include sedimentation
separation and density gradient separation. Other
methods are based on functional properties of cells such as
adhesive or phagocytic properties. Selected mononuclear cell
types can adhere to plastic surfaces or to nylon wool. Other
techniques employ selective depletion of cells such as lymphocytes
undergoing proliferation. Mitogens in culture can
be employed to select given lymphocyte populations based
on their ability to respond to these stimulants. Rosetting techniques
permit the detection or purification of cells expressing
a certain surface receptor for antigen. Immunoselection techniques
employ either monoclonal or polyclonal antibodies
Culture
medium
containing
51 Cr
Target cells (chromium-labeled)
Stimulating (sensitizing) cells
Responding (effector) cells
C