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mixed lymphocyte reaction (MLR) 501 MNS blood group system
of histoincompatibility between the two individuals donating
the lymphocytes. The lymphocyte antigens of these
genetically dissimilar subjects stimulate DNA synthesis by
each other which is measured by tritiated thymidine uptake
assayed in a scintillation counter. Refer to mixed lymphocyte
reaction (MLR).
mixed lymphocyte reaction (MLR)
Lymphocytes from a potential donor and recipient are combined
in tissue culture. Each of these lymphoid cells has the
ability to respond by proliferating following stimulation by
antigens of the other cells. In the one-way reaction, the donor
cells are treated with mitomycin or irradiation to render them
incapable of proliferation. Thus, the donor antigens stimulate
the untreated responder cells. Antigenic specificities
of the stimulator cells absent in the responder cells lead to
blastogenesis of the responder lymphocytes and a subsequent
increase in the synthesis of DNA and cell division. This
process is followed by introduction of a measured amount
of tritiated thymidine, which is incorporated into the newly
synthesized DNA. In the two-way MLR, lymphoid cells from
two individuals are incubated together and total proliferation
is measured. The mixed lymphocyte reaction usually
measures a proliferative response and not an effector cell
killing response. The test is important in bone marrow and
organ transplantation to evaluate the degree of histoincompatibility
between donor and recipient. Both CD4 + and Cd8 +
T lymphocytes proliferate and secrete cytokines in the MLR.
Also called mixed lymphocyte culture.
mixed vaccine
A preparation intended for protective immunization that
contains antigens of more than one pathogenic microorganism.
Thus, it induces immunity against those disease agents
whose antigens are represented in the vaccine. It may also
be called a polyvalent vaccine.
MK-571
A powerful synthetic antagonist of leukotriene D 4 receptor
that prevents bronchoconstriction induced by exercise in
patients with asthma.
MLC
Acronym for mixed lymphocyte culture.
MLD (minimum lethal dose)
That dose of a substance or agent that will kill 100% of the
population tested. Ehrlich defined MLD as the least amount
of a toxin that will kill a 250-g guinea pig within 4 days
after subcutaneous injection.
MLNS (mucocutaneous lymph node syndrome)
Refer to Kawasaki’s disease.
Mls antigens
Minor lymphocyte-stimulating antigens; cell surface
molecules originally observed on mouse cells that stimulate
previously unsensitized T lymphocytes. They occur in two
stimulatory forms designated Mlsa and Mlsc. The Vβ chain
of the T cell receptor is encoded by the Mls genes. The
anti-Mls response is linked to T lymphocyte receptor Vβ
expression. The anti-Mls responses also link to intrathymic
contact of CD8 + T lymphocytes and are critical in the
induction of immunologic tolerance. As the immune system
matures, clones of autoreactive T lymphocytes expressing
the T cell receptor Vβ chain are deleted.
Mls genes
Minor lymphocyte-stimulating genes. Mouse mammary
tumor retroviruses code for Mls genes. The proteins formed
serve as superantigens that are powerful inducers of CD4 +
T lymphocyte proliferation in mixed lymphocyte cultures.
M macroglobulin
An IgM paraprotein that occurs in Waldenström’s
macroglobulinemia.
MMR vaccine
Measles–mumps–rubella vaccine. A live attenuated virus
vaccine given at 15 months of age or earlier. A booster
injection is given later. The vaccine is effective in stimulating
protective immunity in most cases. It may prove ineffective
in children younger than 15 months of age if they
still have transferred antibodies from their mothers. This
vaccine should not be given to pregnant women, immunodeficient
individuals undergoing immunosuppressive
therapy, or patients with acute febrile disease.
MNS Blood Group System
Reactions Phenotype Frequency
Anti-M Anti-N Phenotype Caucasian
African
American
+ 0 M+N– 28 26
+ + M+N+ 50 45
0 + M–N+ 22 30
Anti-s Anti-s
+ 0 S+s– 11 3
+ + S+s+ 43 28
0 + S–s+ 45 69
0 0 S–s– 0