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microinjection 494 microorganisms
Major histocompatibility complex (MHC) genes encode the major histocompatibility antigens that are expressed on cell membranes. MHC genes in the
mouse are located at the H-2 locus on chromosome 17, and MHC genes in humans are located at the HLA locus on the short arm of chromosome 6.
I. II. III.
HLA-A1
CD8 HLA-A1
TcR Virus
TcR
Lysis
Bence–Jones proteins in the serum or urine are examples.
β 2 microglobulin that is a constituent of major histocompatibility
complex (MHC) class I molecules is another
example.
microinjection
A technique for introducing a solution of DNA into a pronuclear
cell or blastocyst using a fine microcapillary pipet.
microlymphocytotoxicity
A widely used technique for human leukocyte antigen
(HLA) tissue typing. Lymphocytes are separated from
heparinized blood samples by layering over Ficoll-
Hypaque, centrifuging and removing lymphocytes from
the interface or by using beads. After appropriate washing,
these purified lymphocyte preparations are counted, and
aliquots are dispensed into microtiter plate wells containing
predispensed quantities of antibody. When used for
human histocompatibility HLA testing, antisera in the
wells are specific for known HLA antigenic specificities.
After incubation of the cells and antisera, rabbit complement
is added, and the plates are again incubated. The
HLA-A1 HLA-A1 HLA-A2 HLA-A2 HLA-A2
HLA-A2
No lysis
Major histocompatibility (MHC) restriction.
Lysis
extent of cytotoxicity induced is determined by incubating
the cells with Trypan blue, which enters dead cells and
stains them blue, while leaving live cells unstained. The
plates are read with an inverted phase contrast microscope.
A scoring system from 0 to 8 (8 implies >80% of
target cells killed) indicates cytotoxicity. Most of the sera
used to date are multispecific because they were obtained
from multiparous females who were sensitized during
pregnancy by HLA antigens determined by their spouses.
Monoclonal antibodies are used with increasing frequency
in tissue typing. This technique is useful to identify
HLA-A, HLA-B, and HLA-C antigens. When purified B
cell preparations and specific antibodies against B cell
antigens are employed, HLA-DR and HLA-DQ antigens
can be identified.
microorganisms
Microscopic life forms that are mostly unicellular, with the
exception of selected fungi. The term may apply to bacteria,
yeast and other fungi, and protozoa, all of which have been
implicated in human diseases.