Untitled - D Ank Unlimited

lymphokine 469 lysis
Fabricius in birds, and other lymphoid organs for which the
predominant cell type is the lymphocyte.
lymphokine
A nonimmunoglobulin polypeptide substance, i.e., a cytokine
synthesized mainly by T lymphocytes that affects the function
of other cells. It may enhance or suppress an immune
response. Lymphokines may facilitate cell proliferation,
growth, and differentiation, and they may act on gene transcription
to regulate cell function. Lymphokines exert paracrine
or autocrine effects. Many lymphokines have now been
described. Well known examples include interleukin-2 (IL2),
IL3, migration inhibitory factor (MIF), and interferon-γ
(IFN-γ). The term cytokine includes lymphokines and soluble
products produced by lymphocytes, as well as monokines
and soluble products produced by monocytes. Lymphokines
are more frequently known as cytokines formed by lymphocytes,
soluble protein mediators of immune responses.
lymphokine-activated killer (LAK) cells
Lymphoid cells derived from normal or tumor patients
cultured in medium with recombinant interleukin-2 (IL2)
become capable of lysing natural killer (NK)-resistant tumor
cells as revealed by 51 Cr-release cytotoxicity assays. These
cells are also known as lymphokine-activated killer cells.
Most LAK activity is derived from NK cells. The large granular
lymphocytes (LGLs) contain all LAK precursor activity
and all active NK cells. In accord with the phenotype of precursor
cells, LAK effector cells are also granular lymphocytes
expressing markers associated with human NK cells. The
asialo G 1+m population, known to be expressed by murine NK
cells, contains most LAK precursor activity. Essentially all
LAK activity resides in the LGL population in rats. LAK cell
and IL2 immunotherapy has been employed in human cancer
patients with a variety of histological tumor types when conventional
therapy has been unsuccessful. Approximately one
fourth of LAK- and IL2-treated patients manifested significant
responses, and some individuals experienced complete
remissions. Serious side effects include fluid retention and
pulmonary edema attributable to the administration of IL2.
lymphoma
A malignant neoplasm of lymphoid cells. Hodgkin disease,
non-Hodgkin lymphoma, and Burkitt’s lymphoma are
examples. Lymphomas or lymphocyte tumors grow in
lymphoid or other tissues but fail to enter the blood in large
numbers. The numerous types of lymphomas are characterized
by various classes of transformed lymphoid cells.
Lymphomas often manifest the phenotype of the normal
lymphocytes from which they arose.
lymphoma belt
An area across central Africa on both sides of the Equator
where an increased incidence of Epstein–Barr virus (EBV)induced
Burkitt’s lymphoma occurs. Burkitt’s lymphoma is
a relatively common childhood cancer in Uganda.
lymphomatoid granulomatosis
Vasculitis in the lung of unknown etiology with an ominous
prognosis. Atypical lymphocytes and plasma cells extensively
infiltrate the pulmonary vasculature. Many of these
lymphocytes undergo mitosis. The lungs may develop cavities,
and occasionally the nervous system, skin, and kidneys
may be sites of nodular vasculitis.
lymphomatosis
Numerous lymphomas occurring in different parts of the
body, such as those occurring in Hodgkin disease.
lymphopenia
A decrease below normal in the number of lymphocytes in
the peripheral blood.
lymphopoiesis
The differentiation of hematopoietic stem cells into common
lymphoid progenitors and ultimately into lymphocytes.
lymphoreticular
A system composed of lymphocytes, monocytes–macrophages,
and the stromal elements that support them. The
thymus, lymph nodes, spleen, tonsils, bone marrow, Peyer’s
patches, and avian bursa of Fabricius comprise the lymphoreticular
tissues.
lymphorrhages
Accumulations of lymphocytes in inflamed muscle in
selected muscle diseases such as myasthenia gravis.
lymphotactin (Ltn)
A member of the γ or C family of chemokines. Human lymphotactin
(Ltn) resembles some β chemokines but is lacking
the first and third cysteine residues characteristic of the α
and β chemokines. Ltn is chemotactic for lymphocytes but
not monocytes and employs a unique receptor. An ATAC
cDNA clone derived from human T cell activation genes
encodes a protein 73.8% identical to mouse lymphotactin.
Tissue sources include thymocytes and activated T cells. T
lymphocytes are the target cells.
lymphotoxin (LT)
A T lymphocyte lymphokine produced by some CD4 +
T cells; it is a heterodimeric glycoprotein comprised
of 5- and 15-kDa protein fragments. Lymphotoxin is
inhibitory to the growth of tumors in vitro and in vivo,
and it also blocks chemical-, carcinogen-, and ultraviolet
light-induced transformation of cells. Lymphotoxin
has cytolytic or cytostatic properties for tumor cells that
are sensitive to it. Approximately three quarters of the
amino acid sequences of human and mouse lymphotoxins
are identical. Human lymphotoxin has 205-amino
acid residues and the mouse variety has 202-amino acid
residues. Lymphotoxin does not produce membrane pores
in its target cells, such as those produced by perforin or
complement, but it is taken into cells after it is bound to
their surfaces and subsequently interferes with metabolism.
Lymphotoxin is also called tumor necrosis factor
β (TNF-β). This T cell cytokine is homologous to and
binds to the same receptors as TNF. It is proinflammatory,
activating both endothelial cells and neutrophils. It
is necessary for normal lymphoid organ development. A
surface form on T cells is mainly a heterotrimer of one
LTα subunit with two LTβ molecules (LTα 1β2). LTα and
LTβ are related to TNF-α, sharing sequence and structural
characteristics in addition to a tight genetic linkage.
TNFα, LTα, and LTα 1β2 all bind to TNF receptor family
molecules.
lysins
Factors such as antibodies and complement or microbial
toxins that induce cell lysis. For an antibody to demonstrate
this capacity, it must be able to fix complement.
lysis
Disruption of cells due to interruption of their membrane
integrity. This may be accomplished nonspecifically, as
with hypotonic salt solution, or via interactions of surface
membrane epitopes with specific antibody and complement
or with cytotoxic T lymphocytes.
L