Untitled - D Ank Unlimited

N addition
Appending nucleotides by terminal deoxynucleotidyl transferase
during D–J joining or V to-D–J joining.
naïve
B and T lymphocytes that have not been exposed to antigen.
Also called unprimed or virgin lymphocytes.
naïve B cell
A mature lymphocyte that has exited the bone marrow but
has not yet come into contact with the antigen for which it
is specific.
naïve lymphocyte
Mature T or B lymphocytes that have never been exposed to
antigen and are not derived from antigen-stimulated mature
lymphocytes. Exposure of naïve lymphocytes to antigen
leads to their differentiation into effector lymphocytes such
as antibody-secreting B cells or helper T cells and cytolytic
T lymphocytes (CTLs). Lymphocytes that migrate from the
central lymphoid organs are naïve (e.g., naïve T cells from
the thymus and naïve B cells from the bone marrow). The
surface markers and recirculation patterns of naïve lymphocytes
differ from those of lymphocytes activated previously.
Also termed unprimed or virgin lymphocytes.
naïve T cell
A mature T lymphocyte that has exited the thymus but has not
yet come into contact with the antigen for which it is specific.
naked DNA vaccine
An immunizing preparation composed of an isolated DNA
plasmid that encodes the vaccine antigen. Following introduction
into the host body, the plasmid becomes incorporated
into the host cells that form pathogen protein.
NALT
Abbreviation for nasopharynx-associated lymphoid tissue.
Refer also to MALT.
NANBH
The principal cause of transfusion-related hepatitis. Risk
factors include intravenous drug abuse (42%), unknown risk
factors (40%), sexual contact (6%), blood transfusion (6%),
household contact (3%), and health professional occupations
(2%). Of the 150,000 cases per year in the United States, 30
to 50% become chronic carriers, and one fifth develop cirrhosis.
Parental NANBH is usually hepatitis C, and enteric
NANBH is usually hepatitis E.
NAP
Neutrophil alkaline phosphatase.
NAP-1
Neutrophil attractant or activation protein-1. Refer to interleukin-8
(IL8).
NAP-2 (neutrophil activating protein 2)
A chemokine of the α (CXC) family. NAP-2 is a proteolytic
fragment of platelet basic protein (PBP) corresponding
to amino acids 25 to 94. CTAP-III and LA-PF4 or β-TG
released from activated platelets are inactive NAP-2 precursors.
Leukocytes and leukocyte-derived proteases convert
N
the inactive precursors into NAP-2 by proteolytic cleavage
at the N terminus. Platelets represent the tissue source.
naprosyn
A nonsteroidal anti-inflammatory drug (NSAID).
naproxen (2-naphthaleneacetic acid, 6-methoxy-α-methyl)
An anti-inflammatory drug used in the treatment of arthritis,
especially rheumatoid arthritis of children and adults, as
well as ankylosing spondylitis.
nasopharyngeal-associated lymphoreticular tissue (NALT)
Tissue that includes the palatine and nasopharyngeal tonsils
(adenoids) that are mostly covered by squamous epithelium.
The palatine tonsils usually contain 10 to 20 crypts
that increase their surface area. The deeper regions of
these crypts contain M cells that may take up encountered
antigens. The tonsils contain all major classes of antigenpresenting
cells, including dendritic and Langerhans’ cells,
macrophages, class I-positive B cells, and antigen-retaining
follicular dendritic cells in B cell germinal centers.
Approximately one half of tonsillar cells are B lymphocytes
situated mainly in follicles containing germinal
centers. Immunoglobulin G (IgG) blasts are predominant
in germinal centers; plasma cells, in the parafollicular area.
Approximately 40% of tonsillar cells are T cells, and more
than 98% express the αβ TCR. Higher CD4:CD8 ratios are
found in tonsils compared with peripheral blood. The tonsils
reveal not only features of mucosal inductive sites but
also characteristics of effector sites with high numbers of
plasma cells. The role of tonsils in host mucosal immunity
following intranasal immunization remains to be determined.
NALT also includes diffuse aggregates of lymphocytes
in the upper respiratory epithelium.
native immunity
Genetically determined host responsiveness that prevents
healthy humans from becoming infected under normal
circumstances by selected microorganisms that usually
infect animals. This may be altered in the case of profound
immunosuppression of humans, as in the case of
acquired immune deficiency syndrome (AIDS), in which
humans become infected with microorganisms such as
Mycobacterium avium intracellulare.
natural antibody
Polyreactive antibodies (principally IgM antibodies) found
in the serum of an individual who has no known previous
contact with that antigen such as by previous immunization
or infection with a microorganism containing the antigen.
The anti-A and anti-B antibodies related to the ABO blood
group system are natural antibodies. Natural antibodies
may be consequences of exposure to cross reacting antigens
(e.g., ABO blood group antibodies resulting from exposure
to bacterial antigens in the gut). Also refers to immunoglobulin
M (IgM) antibodies produced by B-1 (CD5 + ) cells
specific for microorganisms found in the environment and
gastrointestinal tract. The two kinds of natural antibodies in
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