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everse transcriptase–polymerase chain reaction 622 rhesus antigen
B Lymphocyte
(Plasma cell)
Antibody
release
Anti-Ig
into host cell DNA. It also permits RNA sequences to be
converted into complementary DNA (cDNA) and cloned.
Problems in proofreading may lead to introduction of a considerable
number of mutations into the DNA. It is encoded
by human immunodeficiency virus (HIV), and the purified
form is used to clone complementary DNAs encoding
a gene of interest from messenger RNA. Inhibitors of the
enzyme have been used as therapy for HIV-1 infection.
reverse transcriptase–polymerase chain reaction
(RT-PCR)
A technique employed to amplify RNA sequences. Reverse
transcriptase is used to convert an RNA sequence into a
complementary DNA (cDNA) sequence that is amplified by
PCR using gene-specific primers. This technique is a variation
of the polymerase chain reaction employed to amplify a
complementary cDNA of a gene of interest.
reverse vaccinology
Development of a vaccine antigen based on sequences in a
pathogenic organism’s genome or proteome that are most
likely to represent epitopes that T cells recognize. Also
called epitope-driven vaccine design.
RF
Abbreviation for rheumatoid factor.
RFLP (restriction fragment length polymorphism)
Local DNA sequence variations of humans or other animals
that may be revealed by the use of restriction endonucleases.
These enzymes cut double-stranded DNA at points where they
recognize a very specific oligonucleotide sequence, resulting
in DNA fragments of different lengths that are unique to each
individual. The fragments of different sizes are separated
by electrophoresis. The technique is useful for a variety of
purposes, such as identifying genes associated with neurologic
diseases (e.g., myotonic dystrophy) that are inherited as
autosomal-dominant genes or in documenting chimerism. The
fragments may also be used as genetic markers to help identify
the inheritance patterns of particular genes.
rhabdovirus immunity
Resistance to rabies is in part genetically controlled; in mice,
it is controlled by one or two genes. Resistance is a dominant
trait. Susceptibility to rabies virus infection varies among species.
Immunity may be specific or nonspecific. Interferon plays
a critical role. Rhabdoviruses are very susceptible to interferon
action. In rabies, no serological evidence of infection is found
prior to onset of the disease, which is usually fatal. Vaccination
studies have yielded the most data concerning specific immunity.
Vaccination during the incubation period, if not repeated,
Antibody-coated
erythrocyte
Ig from
B cell
+
Reverse plaque method.
Complement
Complement
mediated red
cell lysis, plaque
formation
can cause the “early death phenomenon.” Passively transferred
specific antibodies can protect against rabies. The relative
significance of cell-mediated immunity as a protective mechanism
remains to be demonstrated, although antibody titers
and protection are closely correlated. Protective mechanisms
following post-exposure treatment of humans with rabies vaccine
involve T lymphocytes. Rabies virus infection progresses
silently in the nervous system without inducing any detectable
humoral immune response. Use of anti-rabies vaccination must
distinguish between preventive vaccination and post-exposure
treatment. Several vaccine injections together with specific
immunoglobulin inoculation are warranted in post-exposure
treatment for humans. Preventive vaccination is usually carried
out in veterinary medicine. Contemporary vaccines confer
partial or no protection against selected rabies-related virus
infections. Only inactivated vaccines are licensed for use in
humans. Those previously used that contained nervous tissue
were dangerous because their myelin content could have
induced hypersensitivity reactions leading to paralysis. Most
current vaccines are prepared from virus grown in cell culture.
While attenuated virus vaccines have been used in domestic
animals in the past, newer potent inactivated vaccines have
replaced them. Recombinant vaccines make use of a vaccinia
recombinant virus containing the rabies virus glycoprotein
gene that induces production of virus glycoprotein in infected
cells to induce rabies virus-neutralizing antibodies and protect
susceptible hosts. It is active by oral administration.
Rh antigens
Refer to rhesus antigen and to rhesus blood group system.
Rh disease
Refer to erythroblastosis fetalis.
Rh factor
Erythrocyte antigen that determines the Rh blood group system.
Refer to rhesus antigen and rhesus blood group system.
Rhazes (Abu Bakr Muhammad ibn Zakariya, 865–932)
Persian philosopher and alchemist who described measles
and smallpox as different diseases. He was also a proponent
of the theory that immunity is acquired and is often cited as
the premier physician of Islam.
rhesus antibody
An antibody reactive with rhesus antigen, especially RhD.
rhesus antigen
Erythrocyte antigen of humans that shares epitopes in common
with rhesus monkey red blood cells. Rhesus antigens
are encoded by allelic genes. D antigen has the greatest clinical
significance as it may stimulate antibodies in subjects