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Ricinus communis 627 RNA polymerase (RNAP)
Charles Robert Richet.
Ricinus communis
Refer to ricin.
Rickettsia immunity
The immune response in rickettsial infection involves powerful
and persistent humoral and cell-mediated responses.
Antibodies act as opsonins that render microorganisms susceptible
to destruction by macrophages even though complement
and antibody are not bactericidal. Antibody-dependent
cellular cytotoxicity has also been demonstrated. Interferon-γ
(IFN-γ)-activated macrophages effectively destroy rickettsia.
Interferon-γ and to a lesser degree tumor necrosis factor
(TNF) can control reproduction of rickettsiae in nonprofessional
phagocytes. Protection depends upon cell-mediated
immunity rather than antibody alone. Rickettsial infections
activate natural killer (NK) cells. Both LAK and cytotoxic
T cells can kill rickettsia-infected cells. Numerous attenuated
rickettsial and killed subunit vaccines are available.
Rieckenberg reaction
A trypanosome immune adherence test. Anticoagulated
blood of an animal that recovered from trypanosomiasis
is combined with live trypanosomes. Provided the same
antigenic type of trypanosome that produced the infection is
used for the test, blood platelets adhere to the trypanosomes.
rinderpest vaccines
Although several types have been used in the past, the most
satisfactory contemporary vaccine contains a virus adapted
to tissue culture.
ring precipitation test
Refer to ring test.
ring test
A qualitative precipitin test used for more than a century
in which soluble antigen (or antibody) is layered onto an
antibody (or antigen) solution in a serological tube or capillary
tube without agitating or mixing the two layers. If the
antigen and antibody are specific for one another, a ring of
precipitate will form at the interface. This simple technique
was among the first antigen–antibody tests.
Antigen
Antibody
Precipitation test, lattice formation.
RIST
Refer to radioimmunosorbent test.
rituxan
An anti-cancer monoclonal antibody that serves as a type
of biotherapy by binding to tumor cells and triggering the
immune system to kill target tumor cells rather than using
toxic chemicals to accomplish this result. The antibody has
been approved by the FDA for use in patients with non-
Hodgkin lymphoma.
rituximab
A chimeric murine–human monoclonal IgG 1 (human
Fc) that unites with the CD20 molecule on normal and
malignant B cells and is used to treat patients with relapsed
or refractory low-grade or follicular B cell non-Hodgkin
lymphoma. It acts by complement-mediated lysis, antibodydependent
cellular cytotoxicity, and apoptosis of malignant
lymphoma cells.
RNA-directed DNA polymerase (reverse transcriptase)
DNA polymerase present in retroviruses such as human
immunodeficiency virus (HIV) and Rous sarcoma virus
that can use an RNA template to produce DNA. The primer
needed must contain a free 3′ hydroxyl group that is basepaired
with the template. This produces a DNA–RNA
hybrid. Reverse transcriptase is critical in recombinant
DNA techniques, as it is employed for first-strand cDNA
synthesis.
RNA polymerase (RNAP)
A multiprotein complex comprised of 8 to 14 polypeptides
involved in the transcription of different sets of genes into
RNA. RNAP I, II, and III direct the synthesis of ribosomal
RNA, messenger RNA, and selected small nuclear
or cytoplasmic RNAs, including transfer RNA, respectively.
Each human RNAP is composed of two large subunits
(126 to 192 kDa) and at least six small subunits (14
to 18 kDa), three of which are shared by all three RNAP
classes. Autoantibodies against RNAP I and III are very
specific for systemic sclerosis and may portend a poor
prognosis. Autoantibodies to RNAP II are also associated
with systemic sclerosis. Although initially believed to be
diagnostic for systemic sclerosis, autoantibodies against
RNAP II have also been detected in patients with systemic
lupus erythematosus (SLE) and overlap syndromes.
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