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lymphocyte antigen stimulation test 465 lymphocyte-function-associated antigen-3 (LFA-3)
interactions. Cytokines play important heavy chain isotype
and provide amplification mechanisms through argumentation
of B lymphocyte proliferation and differentiation.
Germinal centers are the sites of synthesis of antibodies of
high affinity and of memory B cells.
lymphocyte antigen stimulation test
An assay for the in vitro assessment of impaired cellmediated
immunity. It is useful to evaluate patients with
genetic or acquired immunodeficiencies, bacterial and viral
infections, cancers, autoimmune disorders, transplantationrelated
disorders, antisperm antbodies, and previous exposures
to a variety of antigens, allergens, pathogens, metals,
and chemicals. Lymphocyte antigen stimulation is assayed
by [ 3 H]-thymidine uptake or a flow cytometric assay (based
on expression of the activation antigen CD69) with [ 3 H]thymidine
incorporation. Antigen-stimulated culture supernatants
can be assessed for cytokine production by enzyme
immunoassay (EIA).
lymphocyte chemokine (BLC)
A CSC chemokine that induces B lymphocytes and activated
T cells to enter peripheral lymphoid tissue follicles by
binding to the CXCR5 receptor.
lymphocyte chemotaxis
Lymphocytes comprise a heterogeneous motile cell population.
Both T and B cells recirculate continuously between
the blood and the lymphoid tissues. This recirculating cell
population consists of naïve small lymphocytes that are
not in the cell cycle. Once lymphocytes recognize antigen,
their migration behavior changes. They enter the cell cycle
and exit the recirculatory pool. An adhesion phenotype
changes with loss of L-selectin and loss of affinity for the
high endothelial venule (HEV) cells of lymphoid tissue.
They increase expression and activity of various other
adhesion molecules which prevents them from attaching to
the endothelium at sites of inflammation, to cluster around
antigen-presenting cells, and to interact with target cells
for cytotoxicity. Rather than continuing to monitor the
environment for antigen, the lymphocyte changes to a cell
that mediates effector functions. Interleukin-2 (IL2) and
IL15 are both excellent chemotactic factors for activated T
lymphocytes. IL16 is also a T cell attractant with selective
activity for CD4 + . Several chemokines including both α
and β types exert activity. B and T cells respond better to
attractants following their activation. Natural killer (NK)
cells activated with IL2 can respond to chemoattractants,
including several chemokines such as MIP-1α, MCP-1,
RANTES, and IL8.
lymphocyte-defined (LD) antigens
Histocompatibility antigens on mammalian cells that
induce reactivity in a mixed-lymphocyte culture (MLC) or
mixed-lymphocyte reaction.
lymphocyte determinant
Target cell epitopes identified by lymphocytes rather than
antibodies from a specifically immunized host.
lymphocyte-function-associated antigen-1 (LFA-1)
A leukocyte integrin that facilitates lymphocyte adhesion to
endothelial cells and antigen-presenting cells. A glycoprotein
comprised of a 180-kDa α chain and a 95-kDa β chain
expressed on lymphocyte and phagocytic cell membranes.
The ligand of LFA-1 is the intercellular adhesion molecule 1
(ICAM-1). It facilitates natural killer (NK) cell and cytotoxic
T cell interaction with target cells. Complement receptor 3
Lymphocyte-function-associated antigen 1 (LFA-1).
Lymphocyte-function-associated antigen-1 (LFA-1) I domain.
and p150,95 share the same specificity of the 769-amino acid
residue β chain found in LFA-1. A gene on chromosome 16
encodes the α chain and a gene on chromosome 21 encodes
the β chain. This leukocyte integrin (β 2) adhesion molecule
plays a critical role in adhesion of leukocytes to each other
and to other cells and microbial recognition by phagocytes.
LFA-1 binds not only ICAM-1 but also ICAM-2 or ICAM-3.
LFA-1-dependent cell adhesion is also temperature-, magnesium-,
and cytoskeleton-dependent. LFA-1 induces costimulatory
signals believed to be significant in leukocyte function.
LFA-1 function is critical to most aspects of the immune
response. Refer to CD11a and CD18.
lymphocyte-function-associated antigen-2 (LFA-2)
Refer to CD2.
lymphocyte-function-associated antigen-3 (LFA-3)
An immunoglobulin superfamily cell adhesion molecule
found on antigen-presenting cells, among others, that
facilitates their adhesion to T cells. A 60-kDa polypeptide
chain expressed on the surfaces of B cells, T cells, monocytes,
granulocytes, platelets, fibroblasts, and endothelial
cells of vessels. LFA-3 is the ligand for CD2 and is encoded
by genes on chromosome 1 in humans. LFA-3 or CD58 is
L